Vintage Audio
this section covers some restoration work that I did on my vintage HI-FI gear
Main Internet site | FAQ | Personal
Article #1 | 11:25 AM Monday 02/09/2019

Studer B67 MKII: Introduction

A studio-class machine has a totally different architecture and construction quality than consumer-class ones. For me this is the first studio reel to reel tape machine that I restore. Up until now I restored a lot of consumer decks but working on this thing is sure something new for me. The unit is a monster weighting about 75-80 Kg, all hardware included -- console, VU-meter bridge, speed variator. Moving and handling is very though and requires a lot of energy. Other than that, the construction is very rugged and easy to service.

For some reason I always ran away from European audio gear. Especially from Revox. I don't know exactly why. Maybe because of their ugly looks? Well the ugliness is a relative concept. But nobody can't argue that an AKAI GX-747 is ugly. That is a fact. Studer on the other hand are less ugly and have a somewhat neutral, industrial design. But the sound of these machines is what makes them so sought after by music lovers.

This restoration requires a lot of parts, both electrical and mechanical, and will take me some time to get where I want. It is very difficult for me to resist plugging the unit in the wall-socket to see the nice VU-meters light up. On the other hand I know that these Studer decks have some unobtanium integrated circuits that are easily damaged by faults generated by bad capacitors. This is one of those weird cases where film capacitors fail too. I mean this machine has all of them faulty capacitors: electrolytic (FRAKO and Philips), tantalum (ITT), and film (RIFA). But it also has some of the most interesting capacitors I've ever seen: SAL (solid aluminum) made by Philips in the old days. Construction-wise they employ anodic oxidized aluminum oxide as dielectric and semiconducting solid manganese dioxide as electrolyte. These have a very, very long MTBF rate. Think a few hundred thousands hours of service life at 30 degrees Celsius -- insane.

Mechanically there is nothing to reproach. It is clearly that it was designed with perfection in mind. I can think Telefunken, Nagra, Otari, and some high-end Sony machines that are on par with what the Swiss engineers at Studer did. There might be other out there but I haven't heard of nor seen or hear in real life.

I'm thinking out loud here: what if Studer was built by the Japanese people, with genuine Japanese parts? Other manufacturers wouldn't have had any chance in front of such a machine. Anyway the Studer B67 and A80 models were used as master recorders to capture the sound of many great bands in the early '70s and '80s.

Let's put history aside for now and let's concentrate on the actual restoration. This machine was built in 1982. This qualifies it as one of the last production samples. This means they have corrected most of their youth mistakes. I'm more than happy with this.

Disclaimer: FRAKO, RIFA, ITT, Philips, Roederstein, and the like, all produced great quality parts that were working perfectly throughout the intended lifespan of the machines in which they were installed. The fact that these parts have not aged well is well known in the restoration world. Anyway who would have ever thought these units will be in use some 40+ years after they were designed? No one is to blame for this. Sure Japanese parts of the same era aged better. But they probably had different production techniques.

Article #2 | 02:39 PM Monday 02/09/2019

Studer B67 MKII: Technical Data

This reel to reel tape machine has the following technical characteristics.

TECHNICAL PARAMETERS
ParameterValue
Track System2 track 2 channel stereo/monoaural system
Reel CapacityDIN, CINE, NAB, up to 11.1" reel
Tape Speed38 cm/sec ±0.2% (15 ips)
19 cm/sec ±0.2% (7.5 ips)
9.5 cm/sec ±0.2% (3.75 ips)
Variable Speed±1/2 octave
Wow and Flutter<0.06% at 38 cm/sec
<0.08% at 19 cm/sec
<0.15% WRMS at 9.5 cm/sec
Frequency Response30 Hz - 18,000 Hz (±2 dB) at 38 cm/sec
60 Hz - 15,000 Hz (±1 dB) at 38 cm/sec
30 Hz - 15,000 Hz (±2 dB) at 19 cm/sec
60 Hz - 12,000 Hz (±1 dB) at 19 cm/sec
40 Hz - 10,000 Hz (±2 dB) at 9.5 cm/sec
60 Hz - 8,000 Hz (±1 dB) at 9.5 cm/sec
DistortionCCIR equalization: <1% (1,000 Hz / 320 nWb/m) at 38 cm/sec
CCIR equalization: <2% (1,000 Hz / 510 nWb/m) at 38 cm/sec
NAB equalization: <1% (1,000 Hz / 185 nWb/m) at 38 cm/sec
CCIR equalization: <1% (1,000 Hz / 320 nWb/m) at 19 cm/sec
CCIR equalization: <2% (1,000 Hz / 510 nWb/m) at 19 cm/sec
NAB equalization: <1% (1,000 Hz / 185 nWb/m) at 19 cm/sec
CCIR equalization: <2% (1,000 Hz / 320 nWb/m) at 9.5 cm/sec
CCIR equalization: <31% (1,000 Hz / 510 nWb/m) at 9.5 cm/sec
NAB equalization: <1% (1,000 Hz / 185 nWb/m) at 9.5 cm/sec
Signal to Noise RatioBetter than 56 dB (DIN 45405, 320 nWb/m, 2 track) at 38 cm/sec
Better than 54 dB (DIN 45405, 320 nWb/m, 2 track) at 19 cm/sec
Better than 52 dB (DIN 45405, 320 nWb/m, 2 track) at 9.5 cm/sec
Erase RatioBetter than 75 dB (1,000 Hz)
Cross TalkBetter than 45 dB (1,000 Hz)
Bias Frequency150 kHz
Heads1 x record head
1 x playback head
1 x erase head
Motors1 x AC servo motor for capstan drive
2 x AC motor for reel drive
Real Time CounterUp to 9 h 99 min 59 sec; less than ±0.5%
Power Voltage100 V, 120 V, 140 V, 200 V, 220 V, 240 V at 50 / 60 Hz
Dimensions / Weight488 mm (H), 483 mm (W), 257 mm (D) / 35 Kg
(only tape machine, console not included)

Article #3 | 09:30 AM Tuesday 03/09/2019

Studer B67 MKII: Parts List

I have assembled a parts list for this tape machine. My restoration targets mainly the electrolytic and tantalum capacitors but also some other components. Because I am aiming for maximum reliability and low maintenance, some of the electrolytic capacitors were replaced with film or MLCC counterparts. Below you will find lists consisting of the various parts in this unit.

The schematic value corresponds to what normally can be found in the electrical schematics but the actual parts could vary. Especially electrolytic capacitor voltages -- derating (!?). The recommended value is what I replaced the former part with. The TC inscription signifies a tantalum capacitor while MLCC signifies a multi-layer ceramic capacitor.

Descriptions and Parts Listings

The modular layout of this machine is clearly divided in two sections: tape transport and analog signal processing. The first section contains schematics with mixed analog-digital sections but no audio while the second section contains only audio related circuitry. The VU-meter bridge restoration is covered separately.

Tape Transport Section

First of all there are three safety capacitors directly on the mains supply lines that could benefit from replacement. They are located on the power supply chassis.

Power Supply Chassis
IdentifierSchematicRecommendedMouser Number
C1100 nF / 275 Vacclass X505-MPX21W3100FG00KS
C22200 pF / 250 Vacclass Y505-MPY20W1220FAMSSD
C32200 pF / 250 Vacclass Y505-MPY20W1220FAMSSD
C32200 pF / 250 Vacclass Y505-MPY20W1220FAMSSD

The Power Supply / Stabilizer printed circuit board is coded 1.167.746-81 and is located under the big power transformer.

Power Supply / Stabilizer (1.167.746-81)
IdentifierSchematicRecommendedMouser Number
C14700 uF / 40 V4700 uF / 63 V594-MAL205158472E3
C24700 uF / 40 V4700 uF / 63 V594-MAL205158472E3
C310000 uF / 40 V594-2222-051-57103
C44700 uF / 40 V4700 uF / 63 V594-MAL205158472E3
C5220 uF / 16 V220 uF / 25 V594-2222-118-36221
C63.3 uF / 35 V TC80-T350D335K035AT
C71 uF / 40 V TC1 uF / 50 V TC80-T350B105K050AT
C81 uF / 40 V TC1 uF / 50 V TC80-T350B105K050AT
C9220 uF / 16 V220 uF / 25 V594-2222-118-36221
C103.3 uF / 35 V TC80-T350D335K035AT
C11220 uF / 16 V220 uF / 25 V594-2222-118-36221
C121 uF / 40 V TC1 uF / 50 V TC80-T350B105K050AT
C133.3 uF / 35 V TC80-T350D335K035AT

The Tape Transport Control printed circuit board is coded 1.167.790 is located in the center of the machine. It is very easy to spot as it is the largest single PCB in the whole deck. It comes of very easy by unscrewing only two screws. The PCB assembly comes off together with all the tape transport control buttons.

Note that the red lines below don't need to be ordered. I did so because in my unit these parts were either damaged or I thought they will improve quality. You can safely omit them.

Tape Transport Control (1.167.790)
IdentifierSchematicRecommendedMouser Number
C13.3 uF / 25 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C6220 nF / 100 V505-MKS4.22/100/10P
C7220 nF / 100 V505-MKS4.22/100/10P
C106.8 uF / 6.3 V TC6.8 uF / 25 V MLCC810-FK26X7R1E685K
C123.3 uF / 16 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C143.3 uF / 16 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C153.3 uF / 16 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C163.3 uF / 16 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C173.3 uF / 16 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C233.3 uF / 6.3 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C2533 uF / 10 V TC33 uF / 16 V TCT350H336K016AT
C283.3 uF / 6.3 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C353.3 uF / 6.3 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C31470 uF / 6.3 V470 uF / 16 V594-2222-118-35471
C32100 uF / 16 V100 uF / 25 V594-2222-118-36101
C33100 uF / 16 V100 uF / 25 V594-2222-118-36101
IC1RC4558595-RC4558P
IC2RC4558595-RC4558P
IC3SN75462595-SN75462P
IC4RC4558595-RC4558P
IC8SN74LS02595-SN74LS02N
IC9SN75462595-SN75462P
IC10SN75462595-SN75462P
IC11SN75462595-SN75462P
IC18-pin Socket575-193308
IC28-pin Socket575-193308
IC38-pin Socket575-193308
IC48-pin Socket575-193308
IC58-pin Socket575-193308
IC68-pin Socket575-193308
IC814-pin Socket575-199314
IC98-pin Socket575-193308
IC108-pin Socket575-193308
IC118-pin Socket575-193308
DLQ18-pin Socket575-193308

The Tape Tension Control printed circuit board is coded 1.167.790-11 and soldered directly in upright position on the tape transport control PCB assembly. You don't need to remove it in order to service it.

Tape Tension Control (1.167.790-11)
IdentifierSchematicRecommendedMouser Number
C2031 uF / 35 V TC1 uF / 50 V MLCC810-FK16X5R1H105K
IC201SN74LS00595-SN74LS00N
IC202SN74LS00595-SN74LS00N
IC20114-pin Socket575-199314
IC20214-pin Socket575-199314

The Sensor Board Right printed circuit board is coded 1.167.767-82 and is located next to the right tape guidance roller.

Sensor Board Right (1.167.767-82)
IdentifierSchematicRecommendedMouser Number
C210 uF / 25 V10 uF / 50 V647-UBT1H100MPD

There are two Spooling Motor Control printed circuit boards. They are coded 1.167.764 and are located next to the spooling motors. These PCBs are bolted to the top radiator.

The parts from the table below need to be ordered twice.

Spooling Motor Control (1.167.764)
IdentifierSchematicRecommendedMouser Number
C1470 nF / 150 Vac470 nF / 160 Vac598-474MSR250K
C2470 nF / 150 Vac470 nF / 160 Vac598-474MSR250K
C3470 nF / 150 Vac470 nF / 160 Vac598-474MSR250K
R34.7 Ω / 7 W594-AC070004708JAC00

The Capstan Motor Control printed circuit boards is coded 1.167.775 and is located on the upper part of the unit, bolted to the top radiator.

Capstan Motor Control (1.167.775)
IdentifierSchematicRecommendedMouser Number
C1470 nF / 150 Vac470 nF / 160 Vac598-474MSR250K
R322 Ω / 4.2 W22 Ω / 5 W594-AC05W22R00J

The Capstan Speed Control printed circuit board is coded 1.167.770 and is located on the lower left part of the unit, as you look at it from behind.

Capstan Speed Control (1.167.770)
IdentifierSchematicRecommendedMouser Number
C147 nF / 250 V505-M10.047/250/5P
C247 nF / 250 V505-M10.047/250/5P
C347 nF / 250 V505-M10.047/250/5P
C4100 nF / 100 V505-MKS4.1/250/10P
C54.7 uF / 10 V TC4.7 uF / 25 V MLCC810-FK26X7R1E475K
C71 uF / 35 V TC1 uF / 50 V MLCC810-FK16X5R1H105K
C8100 nF / 100 V505-MKS4.1/250/10P
C9100 nF / 100 V505-MKS4.1/250/10P
C10100 nF / 100 V505-MKS4.1/250/10P
C153.3 uF / 16 V TC3.3 uF / 25 V MLCC810-FK26X7R1E335K
C16220 uF / 3 V TCN/A
C18100 uF / 16 V100 uF / 25 V594-2222-118-36101
C19470 uF / 6.3 V470 uF / 16 V594-2222-118-35471
C20100 uF / 16 V100 uF / 25 V594-2222-118-36101
IC1RC4558595-RC4558P
IC4RC4558595-RC4558P
IC5RC4558595-RC4558P
IC18-pin Socket575-193308
IC28-pin Socket575-193308
IC316-pin Socket575-110433161
IC48-pin Socket575-193308
IC58-pin Socket575-193308

The Variable Speed Control printed circuit board is coded 1.167.780 and is located on the lower right part of the unit, as you look at it from behind You cannot remove (of course you can) the PCB assembly because it has some soldered wires attached. However the wires are long enough so that you could work your way on.

Note that the red lines below don't need to be ordered. I did so because I had the brand new ICs as leftovers from other projects. The old logic ICs work just well as they are but since I will add sockets, I might as well put new ICs in them.

Variable Speed Control (1.167.780)
IdentifierSchematicRecommendedMouser Number
C1100 uF / 16 V100 uF / 25 V594-2222-118-36101
C2100 uF / 16 V100 uF / 25 V594-2222-118-36101
C3100 uF / 16 V100 uF / 25 V594-2222-118-36101
IC1SN74LS132595-SN74LS132N
IC2NE555V595-NE555P
IC3NE555V595-NE555P
IC114-pin Socket575-199314
IC28-pin Socket575-193308
IC38-pin Socket575-193308
IC48-pin Socket575-193308

The Counter printed circuit board is coded 1.167.765 and is located on the lower left part of the unit, as you look at it from behind, just above the capstan speed control PCB assembly.

Note that the red lines below don't need to be ordered. I did so because I had the brand new ICs as leftovers from other projects. The old logic ICs work just well as they are but since I will add sockets, I might as well put new ICs in them.

Counter (1.167.765)
IdentifierSchematicRecommendedMouser Number
C747 uF / 6.3 V TC47 uF / 16 V TCT350J476M016AT
C132200 uF / 6.3 V2200 uF / 16 V594-2222-120-15222
C14220 uF / 16 V220 uF / 25 V594-2222-118-36221
IC1SN74LS14595-SN74LS14N
IC2SN74LS132595-SN74LS132N
IC3SN74LS00595-SN74LS00N
IC4SN74LS00595-SN74LS00N
IC5SN74LS11595-SN74LS11N
IC6SN74LS00595-SN74LS00N
IC7SN74LS00595-SN74LS00N
IC8SN74LS193595-SN74LS193N
IC9SN74LS26595-SN74LS26N
IC10SN74LS86595-SN74LS86AN
IC114-pin Socket575-199314
IC214-pin Socket575-199314
IC314-pin Socket575-199314
IC414-pin Socket575-199314
IC514-pin Socket575-199314
IC614-pin Socket575-199314
IC714-pin Socket575-199314
IC816-pin Socket575-110433161
IC914-pin Socket575-199314
IC1014-pin Socket575-199314
IC1116-pin Socket575-110433161
IC1240-pin Socket575-193640

Audio Section

The Reproduce Amplifier printed circuit boards are coded 1.167.710.81 and in my unit bear the numbers 1 and 2. They are located in the audio boards tray.

The parts from the table below need to be ordered twice. Note that the red lines below don't need to be ordered. I did so because in my unit these parts were either damaged or I thought they will improve quality. You can safely omit them.

Reproduce Amplifier (1.167.710.81)
IdentifierSchematicRecommendedMouser Number
C11000 uF / 16 V1000 uF / 25 V594-2222-120-16102
C71000 uF / 16 V1000 uF / 25 V594-2222-120-16102
C8220 uF / 10 V220 uF / 16 V647-UFG1C221MPM
C9220 uF / 10 V220 uF / 16 V647-UFG1C221MPM
C131000 uF / 16 V1000 uF / 25 V594-2222-120-16102
C171 uF / 16 V TC1 uF / 50 V MLCC810-FK16X5R1H105K
C22100 uF / 16 V100 uF / 25 V647-UFG1E101MPM
C24100 uF / 3 V100 uF / 25 V647-UFG1E101MPM
C25100 uF / 3 V100 uF / 25 V647-UFG1E101MPM
C30150 nF / 100 V150 nF / 250 V505-MKP4.15/250/10P
C32100 uF / 16 V100 uF / 25 V647-UFG1E101MPM
C464.7 nF / 160 V4.7 nF / 1 kV505-MKS4O114703C00JS
R74.7 Ω / 0.5 W71-RN60D4R70FB14
R84.7 Ω / 0.5 W71-RN60D4R70FB14
IC1RC5534NE5534595-NE5534P
IC2RC5534NE5534595-NE5534P
IC3RC5534NE5534595-NE5534P
IC18-pin Socket575-193308
IC28-pin Socket575-193308
IC38-pin Socket575-193308

The Overload Detector printed circuit board is coded 1.067.722 and in my unit bears the number 3. It is located in the audio boards tray. Naturally mine is the stereo version.

Overload Detector (1.067.722)
IdentifierSchematicRecommendedMouser Number
C310 uF / 16 V TC10 uF / 25 V TC80-T350E106M025AT
C610 uF / 16 V TC10 uF / 25 V TC80-T350E106M025AT
C710 uF / 16 V TC10 uF / 25 V TC80-T350E106M025AT
C1310 uF / 16 V TC10 uF / 25 V TC80-T350E106M025AT
C1710 uF / 16 V TC10 uF / 25 V TC80-T350E106M025AT
C1810 uF / 16 V TC10 uF / 25 V TC80-T350E106M025AT
IC114-pin Socket575-199314
IC214-pin Socket575-199314

The Record Amplifier printed circuit boards are coded 1.167.711 and in my unit bear the numbers 4 and 5. They are located in the audio boards tray.

The parts from the table below need to be ordered twice.

Record Amplifier (1.167.711)
IdentifierSchematicRecommendedMouser Number
C447 uF / 20 V TC47 uF / 25 V TC80-T350K476M025AT
C73.3 uF / 35 V TC80-T350D335K035AT
C947 uF / 20 V TC47 uF / 25 V TC80-T350K476M025AT
C1147 uF / 3 V TC47 uF / 6.3 V TC80-T350F476K006AT
C1247 uF / 20 V TC47 uF / 25 V TC80-T350K476M025AT
C1647 uF / 3 V TC47 uF / 6.3 V TC80-T350F476K006AT
C1747 uF / 3 V TC47 uF / 6.3 V TC80-T350F476K006AT
C4247 uF / 20 V TC47 uF / 25 V TC80-T350K476M025AT
C5447 uF / 3 V TC47 uF / 6.3 V TC80-T350F476K006AT
IC1SN7402SN74LS02595-SN74LS02N
IC2RC5534NE5534595-NE5534P
IC3RC5534NE5534595-NE5534P
IC4RC5534NE5534595-NE5534P
IC114-pin Socket575-199314
IC28-pin Socket575-193308
IC38-pin Socket575-193308
IC48-pin Socket575-193308

The Oscillator printed circuit board is coded 1.167.712 and in my unit bears the number 6. It is located in the audio boards tray. I have the version with only two non-polarized capacitors near the main connector. I think it is the later variant.

Oscillator (1.167.712)
IdentifierSchematicRecommendedMouser Number
C347 uF / 35 V47 uF / 63 V594-2222-118-38479
C510 uF / 35 V10 uF / 100 V647-UKZ2A100MPM
C710 uF / 35 V10 uF / 100 V647-UKZ2A100MPM
C81 uF / 35 V1 uF / 50 V FILMN/A

The Stabilizer printed circuit board is coded 1.167.713 and in my unit bears the number 7. It is located in the audio boards tray.

Stabilizer (1.167.713)
IdentifierSchematicRecommendedMouser Number
C147 uF / 16 V TC47 uF / 25 V TC80-T350K476M025AT
C247 uF / 16 V TC47 uF / 25 V TC80-T350K476M025AT
C410 uF / 100 V47 uF / 100 V594-2222-120-19479
C510 uF / 100 V47 uF / 100 V594-2222-120-19479
C647 uF / 16 V TC47 uF / 25 V TC80-T350K476M025AT
C847 uF / 16 V TC47 uF / 25 V TC80-T350K476M025AT

VU-meter Bridge

The VU-meter bridge contains the VU-meters, various input-reproduction controls, and the monitor amplifier. There are a few parts that need to be changed here.

The Monitor Amplifier printed circuit board is coded 1.081.908 and it is socketed into the monitor panel PCB assembly behind the monitoring speaker.

Monitor Amplifier (1.081.908)
IdentifierSchematicRecommendedMouser Number
C21000 uF / 16 V1000 uF / 25 V594-2222-120-16102
C31000 uF / 16 V1000 uF / 25 V594-2222-120-16102
C433 uF / 10 V TC33 uF / 16 V TCT350H336K016AT
IC2RC5534NE5534595-NE5534P
IC18-pin Socket575-193308

The Monitor Panel printed circuit board is coded 1.081.900 and it is home to the input-reproduce switch, channel switches, headphones socket, and volume control. It is located behind the monitoring speaker.

Monitor Amplifier (1.081.908)
IdentifierSchematicRecommendedMouser Number
C1470 nF / 16 V TC470 nF / 25 V MLCC810-FK28X5R1E474K
C2470 nF / 16 V TC470 nF / 25 V MLCC810-FK28X5R1E474K
C3470 nF / 16 V TC470 nF / 25 V MLCC810-FK28X5R1E474K
C4470 nF / 16 V TC470 nF / 25 V MLCC810-FK28X5R1E474K
C51 uF / 16 V TC1 uF / 50 V MLCC810-FK16X5R1H105K
C61 uF / 16 V TC1 uF / 50 V MLCC810-FK16X5R1H105K
C71 uF / 16 V TC1 uF / 50 V MLCC810-FK16X5R1H105K
C81 uF / 16 V TC1 uF / 50 V MLCC810-FK16X5R1H105K

This is a very complex machine and it deserves a lot of respect. If you decide to do the restoration then do not hurry, take your time and do the job once. And do it well. Use quality parts. And again, take your time.

Article #4 | 01:28 PM Sunday 08/09/2019

Studer B67 MKII: Restoration

There are a lot of printed circuit boards that require removal before attempting any parts exchange. Some are insanely easy to remove and service, and some are a little bit more difficult. There are single layer and double layer boards. Some have solder mask on both layers, some have only on one layer. Desoldering might be tricky at times. But nothing to be scared of if you have the right tools and the necessary patience. Thankfully everything is serviceable. However note that there are a few integrated circuits that cannot be obtained anymore. I am talking about the TDA 1000 capstan motor controller circuit and the tape transport command mask programmed circuit. Of course both can be emulated with modern microcontrollers. TDA 1000 would be harder to emulate but the other one is simpler and requires only a very good understanding of the electrical schematic. However I am not planning to emulate anything. I'm pretty sure I could do both of them but the amount of work is inhuman. I'd better prefer designing microcomputers instead.

Sure there are other vintage ICs that once fried you will have a hard time getting them. But not as hard as the ones mentioned above. And they can be easily substituted, even though pin-compatibility will be compromised. But this is another subject. Some integrated circuits in my unit presented some sort of corrosion on their terminals: they turned black. This kind of corrosion is easily removed by scraping the leads. But from my experience with older Japanese parts that suffer from a similar disease, it is better to replace these with new parts. So I did. I also replaced the sockets wherever I found appropriate (or not).

One thing I like is that I found the service manual easily on the Internet and it is very comprehensive. Furthermore some of the schematics are hand drawn. Very human-esque. However in my unit on some of the printed circuit boards I have found some electrolytic capacitors with double the voltage specified in the schematics. Not a problem by all means, but so that you know.

An annoying fact is that the Studer engineers have used a lot of axial capacitors on various printed circuit boards. Sure these can easily be changed with radial types with insulated leads. But in order to keep originality I am going to use axial types as well. Vishay still makes them in high quality.

This machine is made in 1982, judging by the dates stamped on various printed circuit boards. Some boards are stamped 1981. The motors are built in 1982, so is the chassis. I think this is one of the latter revisions of the deck because I can see that they have improved the quality of some of the electronic components inside. There are absolutely no red tantalum capacitors and in some places where FRAKO electrolytic capacitors would've been installed, there are Philips parts instead. Speaking of tantalum, only a few of them are made by ITT (blue colored) and are mostly installed in the audio PCB assemblies. The logic boards have green tantalum capacitors. From my experience these are very stable and there is little concern about them. But I trust modern Kemet capacitors even more so I will replace them all. In some cases I will even use MLCC parts instead of tantalum. This will ensure better stability and reliability. It might be overkill in some cases but still. This reel to reel tape deck deserves the best.

What I like most about servicing this deck is that the PCBs are of very good quality. The tracks are very resistant and the through plated holes are very sturdy. However the soldermask is very soft. Don't ever think about pressing the iron too hard on it or it will leave a scratch. But overall from the units that I fixed or restored throughout the time, this one has the best PCBs.

Let's go ahead then.

General Considerations

I should begin by saying that working on this reel to reel tape machine presents a very big health hazard. There are lethal voltages inside. Not knowing what you are doing might result in severe accidents and possibly death by electrocution. I am very skilled in electronics repair and I have been doing such repairs for almost 20 years. This qualifies me to work in this field. But if you do not have experience, please take this information just as a knowledge base. Do not attempt to repair something that you cannot handle as there is a big probability to severe it further while also suffering accidents.

Good working condition tools are also necessary for this restoration. I am using a quality temperature regulated soldering station with multiple tips for every situation that I could possibly encounter. Also I am using a good solder pump and quality desoldering wick in two sizes. Isopropyl alcohol is handy to decontaminate boards of old flux and other residues. I also use eutectic formulation quality solder. Every replacement part is brand new, from a reputable manufacturer, ordered from U.S.A., Japan, or Germany. Also I only use parts that are suitable as replacements in various sections of the machine, after inspecting and comprehending the original schematic. Last but not least I have the years of experience backing up every action that I take while working on this unit.

I have found out that working with a temperature of 285 to 290 degrees Celsius is sane for these Studer vintage printed circuit boards. Keep in mind that parts fitted to large ground planes require 300 to 305 degrees Celsius. I have never lifted a pad with this temperature. But it is also true that I never wait more than three seconds with the soldering tip on a pad.

Flux fumes are extremely toxic and should be avoided at all costs. Especially toxic are the fumes released while working on these old electronic boards.

Tape Transport Section

The tape transport section consists of restorations of the various printed circuit boards that control the operation of the machine. Think various motor control circuits, solenoid control, (variable) tape speed regulator, digital counter, power supply, and so on.

Power Supply / Stabilizer Restoration

This large PCB is bolted under the power transformer and is easy to remove. You just need a very long Allen key. Or Inbus as they call them in Germany.

This is the board prior to servicing.

And the solder side.

A bunch of small tantalum capacitors are decoupling the input and outputs of the stabilizer integrated circuits. I know they look like power transistors but in fact they are ICs.

The four big FRAKO capacitors have been carefully removed from the PCB assembly. I have tested all of them and -- surprise -- all are in very good shape. All are well within their factory specifications. This is unexpected. I believe this is a low mileage deck. Otherwise I can't explain. In fact they look so well on the tester that I can safely put them back. But at a second thought they are almost 38 years and I know FRAKO parts tend to fail short. I wouldn't want this to happen directly on the power supply rails.

I have found new capacitors employing the exact same fixture as the old ones. However I couldn't find a 10000 uF / 25 V capacitor with dimensions 30 x 40 mm thus I bought a 10000 uF / 40 V part which is slightly larger at 35 x 40 mm. There is enough space on the PCB for this capacitor so no problems here. Only aesthetics are a little bit impacted. If you care, that is.

New tantalum capacitors and big electrolytic capacitors are in position.

This is the solder side after servicing.

Tape Transport Control Restoration

The biggest printed circuit board of them all. It is a little bit difficult to get it out but not impossible, even without clearing the wire loom out of the way. This PCB is home to a mask programmed integrated circuit (a ROM basically) that contains the program that controls the tape transport functions. I am very curious about the internal organization of this ROM. Maybe it can be replicated? It should be a fun project.

Details on various sections of the PCB.

I have changed all but one tantalum capacitors with modern MLCC parts. I replaced one tantalum capacitor with a similar part rated higher in terms of operating voltage. Also I added sockets to all integrated circuits, dual-mosfets, and optocoupler. I have replaced two Philips film capacitors with WIMA parts. This operation is unnecessary though. But I did it anyway.

The circuit board is restored.

Detailed view on restored PCB sections.

Solder side.

Tape Tension Control Restoration

This is a small PCB soldered directly on the tape transport control PCB. I have not removed it nor have I took pictures of it. However I have changed one tantalum capacitor rated 1 uF / 35 V with a modern MLCC part rated 1 uF / 50 V. Also I have added sockets for the two integrated circuits. While here I replaced the old ICs with new ones built by Texas Instruments.

For pictures, please observe the images above in the paragraphs dedicated to the tape transport control circuit board.

Sensor Board Right Restoration

This is a small printed circuit board that is next to the right tape sensor assembly. It is tricky to get out without removing the tape roller but it can be done with much care. There is only one capacitor to replace on this PCB.

This is the board prior to servicing.

And the solder side.

The sole FRAKO capacitor that requires service. In the schematic it is rated 10 uF / 25 V. In my unit a 63 V part was factory-installed. I chose to replace it with a Nichicon BT series part rated 10 uF / 50 V.

After servicing.

View from another angle.

Spooling Motor Control Restoration

These two small printed circuit boards are home of the dreaded RIFA film capacitors. These have developed a habit of cracking, shorting, and eventually smoking out, causing the spooling motors to malfunction. It is recommended to replace the power resistor as well. By now it should already be fatigued. In my unit, one of those power resistors has increased its resistance and is now measuring almost 7 Ω.

This is the board prior to servicing.

And the solder side.

A close-up shot of the RIFA film capacitors. These have 20 mm lead spacing and it is difficult to find modern capacitors that don't come in 22 mm spacing. But most important is the Vac rating of the replacements. It should absolutely not be below 150 Vac. I found some Illinois Capacitor parts that come in 20 mm lead spacing and 160 Vac rating. I think these make for a good replacement.

The new Illinois Capacitor parts are all in. I have used glass beads as spacers. Power resistor has been replaced as well.

Solder side.

Detailed view.

Next up comes the second spooling motor PCB. One of the RIFAs was measuring continuity at 2 Ω and 0 nF capacitance.

And the solder side.

New parts.

New parts have been installed in place.

Solder side is good.

Capstan Motor Control Restoration

This small printed circuit boards is home of one (shot) RIFA film capacitor. On my board the capacitor is measuring 1.5 uF and is cracked badly. The resistor measures OK however. I chose to replace it for safety reasons.

Before servicing.

And the solder side.

Cracked RIFA capacitor is out for good.

PCB is restored.

This is the solder side. I have cleaned up the old flux.

View from another angle.

Capstan Speed Control Restoration

This printed circuit board controls the speed of the capstan motor by means of a quartz locked PLL mechanism. It accepts the feedback from the capstan motor tachogenerator as speed regulation reference. It also has three switches that commute between the three speeds available. This board is also home of the very rare TDA 1000 integrated circuit.

This is the board prior to servicing.

The solder side is hidden beneath an electromagnetic radiation shield.

You can see that the integrated circuits on my PCB are all directly soldered. I decided to socket all of them in order to ease-up future maintenances.

Halfway through the socketing operation. With the right tools you can remove even the most stubborn integrated circuit without damage. I use an Engineer SS-02 solder pump and the soldering station for heating purposes. Unfortunately I don't have a desoldering station.

The precious TDA 1000 integrated circuit is removed from the PCB safely.

Delicate handling and making sure you are not statically charged is very much required when dealing with these (rare) integrated circuits.

While here, I decided to replace all operational amplifiers on this board. They show signs of leg corrosion. Better safe than sorry.

Also I have replaced seven film capacitors. This operation is largely unnecessary but I have my doubts about Philips capacitors in general -- except SAL types. I used WIMA film capacitors of the same rating to replace C1, C2, C3, C4, C8, C9, and C10. As a matter of fact I have measured all the Philips film capacitors that I extracted and absolutely all of them are within their 5% specified tolerance. They all measure perfect. But I had some bad experiences in the past which made me want to replace these. In fact I recommend you to not touch any part (resistor, capacitor, transistor, integrated circuit, and so on) if it is not defect. You know the drill: if it ain't broke, don't fix it.

C5, C7, and C15 were originally tantalum capacitors and I decided to replace them with modern MLCC parts with a bump in operational voltage. I very much trust modern tantalum capacitors but given the fact that this PCB is so expensive, I went the reliability lane.

I couldn't source a Kemet 220 uF / 3 V tantalum capacitor at the time of this restoration. It was simply not available at Mouser. But I am keeping an open eye on them and I'll order one as soon as they come back in stock.

Supply rail filtering capacitors C18, C19, and C20 were FRAKO bombs. I replaced them all with Vishay 118 AHT series parts.

Solder side.

Metallic shield is installed back in position.

View from another angle.

Variable Speed Restoration

This circuit board is bolted to the chassis via two very long hex nuts. Thankfully these are very well secured in place thus you only need to remove two Allen screws and pull this PCB assembly gently from its socket in the distribution PCB. Also this board has some wires soldered to it and servicing it is a little bit awkward. But there is little to do here: change only three electrolytic capacitors.

This is the board prior to servicing.

The solder side as follows.

Of course I have also added augat sockets to all integrated circuits.

Counter Restoration

The tape counter printed circuit board is constructed entirely with TTL integrated circuits. In my unit all but two of the TTL ICs are directly soldered. Some of them present black legs which is a common fault with old Texas Instruments parts. Well I hope you see the quotes, it is not a fault per se but it could be if the corrosion progresses enough. I decided to do a full scale re-socketing of all ICs. While here I chose to swap all of them with new ones that I had lying around the parts drawer. These are remnants of other digital projects that I worked on so giving them a useful life seems like a good idea.

This is the board prior to servicing.

The solder side as follows.

Main counter IC. This is a MOSTEK ion-implanted, P-channel MOS six-decade synchronous up/down counter/display driver with compare register and storage latches. Sounds impressive, eh? It should be. This is 1976 technology after all. Vacuum tubes were still around in big numbers back then.

All unsoldered and PCB pads cleaned.

Components side.

Detailed view.

Sockets are mounted. The capacitors have been changed.

Detailed view. 47 uF capacitor has glass beads as spacers.

All new integrated circuits are in position.

Tilted-frontal view.

Detailed view again.

Solder side looks good too.

This was the most tedious PCB of them all to work on. It was not bad by all means and I had a lot of fun doing it, even if it appears to be a boring job. It all depends on perspective.

Audio Section

The audio section consists of restorations of all the printed circuit boards involved in analog signal processing. That means reproduce and record amplifiers, oscillator, overload detector, and stabilizer. All these PCB assemblies are located in the audio boards tray in the lower part of the tape machine.

Reproduce Amplifier Restoration

There are two reproduce amplifiers located in positions 1 and 2 in the audio boards tray in my machine. They are fairly complicated but thankfully there is not a lot to change on them. The usual suspects are FRAKO electrolytic capacitors, old tantalum capacitors. In addition I am going to add integrated circuit sockets. Also I will fix the bad channel 1 reproduce amplifier because at this moment it is not working at all.

This is the channel 1 PCB before servicing.

And the solder side. Trained eyes will spot a lifted pad.

FRAKO time-bombs and mismatched axial capacitors. Somebody was here before me and replaced one of those big axial FRAKO capacitors with a blue one. He did a messy job. Also he exchanged one of the non-polarized film capacitors next to the trimmer resistors array. It is the second one from the top. The yellow one. The technician also lifted one of the bottom pads of this capacitor and did another messy job adding a wire connector in place of the printed track. Huh...

Scorched 4.7 Ω resistors. One is measuring ~ 380 kΩ and the other one is measuring ~ 680 Ω. Way off limits.

The burned resistors were replaced by Dale RN60D series metal film precision resistors seated on glass beads for better heat dissipation. I tried to clean the PCB as much as I could but some carbonized burn residues were so stubborn that I had to leave them be. Also somebody scratched the soldermask next to one of the 1000 uF capacitors. It wasn't me. I did my share of scratchings but in this case it wasn't me.

The restored printed circuit board looks like this.

This is the solder side after the restoration.

Tilted-frontal view.

More details.

This is the channel 2 PCB before servicing.

And the solder side.

Roederstein capacitors. This is weird but not uncommon. Both Roederstein and FRAKO were high quality at their time. But they both aged badly. Surprisingly all these Roederstein capacitors still measure up to specifications. As a fun fact, I always liked ROE (or ERO, as they called themselves at some point) capacitors.

This is the restored PCB. I have changed all Roederstein and FRAKO capacitors, one Philips Film capacitor, one ITT tantalum capacitor, and two resistors. The resistors were OK but for symmetry and looks I chose to upgrade them to Dale RN60D parts as those used on channel 1 PCB. The Philips film capacitor was OK but I changed it anyway with a WIMA polypropylene film part.

And the solder side.

View from another angle.

Overload Detector Restoration

This is the first printed circuit board that I serviced in this tape deck. I decided to replace the sockets with augat-class ones. Note that this operation is largely unnecessary but since I had these fine sockets around, why not? Note that the original sockets are made by AMP -- very good manufacturer. On this board there are some tantalum bombs made by ITT. The blue drops need to go quickly. It is unlikely that these capacitors will fail in this circuit topology but what if? Yes, they need to go.

This is the PCB before servicing.

And the underside.

Detailed view on the ITT tantalum capacitors. Notice the TBA231A integrated circuits. These are operational amplifiers that are no longer available. But they are equivalent to SN76131 parts made by Texas Instruments. You'll have a hard time sourcing these as well. The other parts around are unlikely to fail so no need to change anything else.

C3, C6, C7, C13, C17, and C18 were all tantalum capacitors rated 10 uF / 16 V. I replaced them all with modern Kemet tantalum capacitors rated 10 uF / 25 V. All these capacitors play the role of stage decoupling or functional parts of high pass filters. The AMP sockets were replaced by augat-class sockets.

Detailed view.

Overview of the serviced printed circuit board.

Detailed view of the soldering job I did on the new integrated circuit sockets. Looks industrial. However a trained eye can easily tell the solder is newer than that of the other terminals around.

Record Amplifier Restoration

There are two record amplifiers located in positions 4 and 5 in the audio boards tray in my machine. Like the reproduce amplifier, these are also fairly complicated. But nothing to be scared of. I've seen my round of printed circuit boards throughout the time.

This is the channel 1 PCB before servicing. Note that somebody before me changed an operational amplifier. I am going to probably change all of them with new parts of the same type.

And the solder side.

The 74LS02 integrated circuit presents black oxide on its legs. It is a candidate for replacement.

I added augat sockets to all integrated circuits. Also all ICs have been replaced with new Texas Instruments parts. All tantalum capacitors were replaced with modern Kemet tantalum parts. There is nothing else to be done on this board.

The restored PCB looks as follows.

The solder side looks OK after servicing.

View from another angle.

This is the channel 2 PCB before servicing.

And the solder side.

View from another angle, just to illustrate the parts density on these PCBs.

All old parts have been changed.

Solder side now looks like this.

View from another angle.

Oscillator Restoration

This is a very simple PCB consisting of only a handful of parts. Very few capacitors need to be replaced here. No other part was touched. FRAKO electrolytic capacitors are know for failing short. In my case however I have put the FRAKOs to test after I have extracted them. To my surprise they were measuring very good, even thought the ESR was a little on the higher side. But I've seen new capacitors measuring worse than these.

Here is the board before servicing.

This is the underside.

C3 was originally rated 47 uF / 35 V and was replaced with a modern axial capacitor rated 47 uF / 63 V. C5 and C7 were rated 10 uF / 35 V in the schematic. In my unit they were at 63 V. I chose to replace them with Nichicon KZ MUSE series parts rated 10 uF / 100 V. Not that the extra voltage bump is required but I had these capacitors lying around. C8 was an electrolytic capacitor rated 1 uF / 35 V and was replaced with a Panasonic ECQ series film capacitor with glass beads as spacers.

Here is the board after servicing.

Details.

And a detailed view on the solder job.

Stabilizer Restoration

This circuit board implements the power supply for the entire audio section. Only a few parts need to be changed here. Namely two electrolytic capacitors and four tantalum capacitors.

Here is the board before the restoration.

This is the solder side.

The restored PCB looks nice with the blue-yellow contrasting colors.

I have used 6 mm height glass tubes as electrolytic capacitor spacers. Better airflow is thus assured and it looks good too.

Kemet tantalum capacitors are trusty in all environments. And this one makes no exception.

The solder side looks good.

VU-meter Bridge

The VU-meter bridge is simple to restore since it has very few parts that require replacement. Everything that needs service is located behind the monitoring speaker panel. Thus it is best to dismantle the hinges and take out the entire speaker assembly.

Like this.

Monitor Amplifier Restoration

This circuit is a classic push-pull amplifier driven by an operational amplifier. Simple and effective. You can't go wrong with this.

And the solder side.

Electrolytic and tantalum capacitors have been changed. I added an augat socket to the integrated circuit and I have replaced the IC with a new one.

Solder side after the work is done looks like this.

Monitor Panel Restoration

The monitor panel consists of only some signal routing switches and four transistor audio buffer circuits. These filters use some small capacity tantalum capacitors that can be quickly replaced with MLCC modern parts.

This is the PCB assembly before.

I have used TDK MLCC capacitors to replace all ITT old ones. Then I brush cleaned the PCB. And it looks like this now.

All done on the VU-meter bridge. I really like the simplicity of these circuits.

The volume potentiometer is cracking a little bit. But it doesn't matter that much since I seldom use the integrated monitoring function. Most of the time, the volume is set to minimum and the input signal switch is set to Input. It is easy to omit the restoration of these small circuits. But a shorted electrolytic capacitor could jeopardize the stabilizer card in the B67 machine. Better safe than sorry.

Overview of Audio Section

Here are the audio section printed circuit boards all socketed in their corresponding place. I have replaced the long PCBs dampening sponge as well. Removing of the old one was a very tedious job and I used acetone because I had no luck with isopropyl alcohool. Acetone stinks and a very well ventilated room is required.

Aftermath

Old parts that have been removed from this reel to reel unit.

Electrolytic capacitors.

Tantalum capacitors.

Film capacitors.

Power electrolytic capacitors and integrated circuit sockets.

Integrated circuits.

Resistors.

Old parts from the VU-meter bridge.

This is all the work I did so far.

Article #5 | 10:53 AM Sunday 15/09/2019

Studer B67 MKII: Replacing the Pinch Roller

This deck was originally equipped with a green adiprene (synthetic rubber) pinch roller. In my case this roller was very gummy and incredibly sticky. Also it was transversally badly cracked.

I immediately started searching for replacements. There are a number of alternatives out there in the wild and I'm not going to enumerate through all of them. But my final decision was to go with an Athan polyurethane roller employing dual ball bearings. This ensures precision movement and reduces wow & flutter. Furthermore the color of this roller is transparent-white which is great for observing the oxide deposits.

The two rollers side by side. You can clearly see the uneven wear on the original green roller.

This is the roller mounted on the tape machine. It looks pretty neat and it works as expected. In fact you can already see the magnetic oxide dust remnants on the edges of the roller.

I have to say that I had my share of fears regarding this roller. I have seen on different audio forums that the shaft needs to be polished with sandpaper in order for the roller to engage correctly on it. I talked with George at Athan before ordering this roller and he reassured me that I couldn't polish the axle by hand with just fine grit sandpaper, even if I tried hard. And I tend to agree with him. Anyway I had no issues inserting this roller onto the axle. It went straightforward with minimal insertion force. Needless to say that I thoroughly cleaned the axle with isopropyl alcohol before putting the new pinch roller on.

Now I have my first chance to listen to a tape. Or more. I hope this pinch roller will last for a long time as it appears to be of a very high quality. I like the dual bearing design and the fact that between the two precision bearings there is a small brass bushing.

Article #6 | 09:00 AM Saturday 21/09/2019

Studer B67 MKII: Varispeed Controller Burned Bulb

The varispeed controller on my unit is directly mounted on the right pillar of the VU-meter bridge. There are two insanely micro-miniature light bulbs. Obviously one of them is burnt out. It is the orange speed-locked indicator. I have never seen a bulb so small. It is smaller than a 3 mm LED. The bulb is designated as 24VA34.

This is the small orange light disperser.

And the small parts inside: a circular spring (inside the orange plastic cap), a spring (visible), and the mini-bulb.

Let's measure this tiny bulb.

So we're looking for a bulb with a length of 8.5 mm, a glass bulb diameter of 2.25 mm, and a metal fixture diameter of 2.75 mm.

I have searched high and low for a bulb so small and eventually found out that it is called Micro Midget Flange T3/4 bulb.

At the moment I am still searching for a supplier of these bulbs.

Article #7 | 11:20 PM Wednesday 25/09/2019

Studer B67 MKII: Impressions

I have listened to a few tapes that I had bought a long time ago from a decommissioned radio station. These are most certainly audio selections for night time since there are some interesting transitions between tracks and also there are very few jingles inter-spread. These tapes contain mostly 1990s Eurodance selections -- not bad by all means.

The tapes are Maxell UD 35-180N recorded on Studer machines. Exact models are unknown to me but radio stations here used A80, B67, and A810. Regardless of what machine they were recorded, the channels are not equal on most of the tracks. But the audio quality is stunning. There are some sections of the tape where the channels are dead spot on. Very good alignment between left and right recording levels.

As I was saying above, I have these tapes for a long time and haven't had any chance of listening to them since I never had a 2-track machine available.

OK enough with the chit-chat on my audio media. Not the best, not the worst. Up until I will have new tapes and time to record on them I need to do with what I have.

So I loaded a tape on the Studer machine and pressed play. The sound is crystal clear and fat. All frequencies are where they need to be. Except for the low end which is a little bit emphasized. Which I like a lot. It can be corrected but I am not going to do it anytime soon.

It's very hard to describe the quality and presence of the sound. The dynamics as well. It is surreal how they managed to design, engineer, and build these machines back then. I mean, for today's audiophiles, having 5 meters of unbalanced XLR-RCA interconnect cables and tantalum capacitors in the signal path would be the recipe of disaster. Also there are no exotic parts installed. Then again the vast majority of bands back in the '70s, '80s, and '90s recorded their albums on Studer reel to reel machines. And they did it with the unmodified machines as they came from the factory. With FRAKO and Roederstein capacitors -- albeit in new condition -- and ITT tantalum bombs in the signal path. Nobody ever complained about this. And these days we listen to CDs, vinyl discs, and hi-resolution audio files all originating on those old master tapes. Think Pink Floyd - The Dark Side of the Moon. It was recorded on Studer A80.

I don't know what to think or say. Studio equipment is part of a different world than that we're used to.

I had a lot of reel to reel tape decks during the past years but none of them sounded or gave the impression of sturdiness like this one does. Now I really can't explain why I ran away from or avoided Revox and Studer. Big mistake.

Enough talking. I have seven Maxell reels that I have to listen, re-listen, identify who's singing, and then decide whether the tape will be reused or kept in its current state. At this moment I'm listening to Ice MC - It's a Rainy Day and for the last 50 minutes or so both channels were equal with peaks at about -2 dB. Conservatively recorded, it seems.

One thing that I observed is that the unit is heating up after two to four hours of continuous use. Now I am really glad I chose high temperature electrolytic capacitors and MLCC / film parts where appropriate. I think most of the heat comes from the motors. Another thing I observed is that after a full speed rewind of an entire tape reel the temperature drops considerably. And since I have to rewind a tape every 90 minutes or so, I don't see this as an issue. Anyway these machines are designed to run 24/7 as broadcast workhorses. Thus I see no problems here.

Article #8 | 09:49 AM Thursday 26/09/2019

Studer B67 MKII: Spare Bulbs for Command Buttons

I noticed that the Stop button is not lighting up. The light bulb must be burned out. I quickly looked on eBay to search for replacement lamps. I have seen some obscene prices and a lot of mystery surrounding the bulb types. Then I did a little research and found out that the bulbs are plain old standard telephone lamps using a T5,5 socket and a 30 V / 40 mA rating. Why such a secretive atmosphere, I don't know.

Anyway I have found someone on eBay selling these telephone lamps at a fair price. And I bought eight clear ones and four green ones. I have now enough spares for the next many years.

Here are the bulbs.

I will use the green ones for the Play button only. The rest of the lamps I will be using for all the other functions. I have even found red bulbs but there is nowhere I could use one. Red designates the recording function. So let's keep it this way.

I don't have the required tool to remove the button caps. But I can improvise: a pliers and some consistent protective material on the sides of the button cap and job done. However this approach is dangerous and requires a lot of patience and care. I decided to remove the front cover and the buttons cover before removing the caps. This operation might be largely unnecessary but since working with metal pliers and plastic caps is dangerous, I took all the necessary precautions.

I have removed the working bulb from the Play button and replaced the burned bulb on the Stop button with it. Then I installed the green lamp in the Play button housing. Stop command button happily lights up now.

Detailed view.

All good so far. I have seen other restorations where people used LEDs to replace these bulbs. I can agree with this solution but as long as original lamps still do exist then why shouldn't I go with this approach? In a way, LEDs are problematic since they require voltage rectification and current limiting resistors. Otherwise they will flicker and their lifespan will be reduced due to inverse voltage constantly being applied on the negative alternating sinewave.

Enough talking and more tape listening is what I need now.

Article #9 | 02:42 PM Saturday 05/10/2019

Studer B67 MKII: Cleaning the Pinch Roller

After playing and recording of a few tapes, inevitably comes the moment to clean the pinch roller. Athan rollers are not to be cleaned with isopropyl alcohol as it will irreversibly damage them. The recommended cleaning solution is soapy water. It sounds like a joke if you've cleaned pinch rollers with IPA in the last thirty years or so.

As skeptical as I could be, I first tried with a cotton swab and tap water. To my surprise the roller cleaned perfectly with only a few swabs and plain old water. No soap whatsoever. I am puzzled. It is either the fact that the roller is new and the oxide deposits were new as well. Or the material this roller is made of is of good quality and the magnetic dust doesn't clog it profoundly.

Later Edit: I found a better way to clean the roller. I gently push it towards the capstan motor axle and while spins I am cleaning it with a cotton swab and water. It works great.

Article #10 | 11:13 AM Friday 25/10/2019

Studer B67 MKII: Recording Audio Program to Tape

I decided to buy a few new tapes for the first time in my life. After analyzing the market I chose the RTM LPR 35 and LPR 90. I bought two of the first type and two of the second. I am very curious of how the Studer will handle these tapes.

Once I opened up the boxes I was greeted with a familiar chlorine (or some similar chemical substance) tape smell. I did some test recordings on 9.5 cm/sec and 19 cm/sec. While 9.5 cm/sec brings up a very nice fat tape sound, 19 cm/sec sounds way better. I briefly tried 38 cm/sec and I was blown away. But let's face it, the tape duration is about 45 minutes. Which is kind of a waste of tape.

I recorded Sandra from FLAC files that I converted from old audio CDs on RTM LPR 90. I also recorded some '80s Italo Disco selections from various vinyl discs on RTM LPR 35. In both cases the tape sounds like the source. Not better, not worse. I went with a maximum peak of 0 dB on the VU-meters. Noise floor was minimal. Smaller than any of my cassette decks. By comparison, my old AKAI GX-535DB tape machine was recording with a strong bass and highs emphasis.

After I finished recording the tapes I gave them a good listen. I couldn't spot any notable audio differences at 9.5 cm/sec between LPR 35 and LPR 90. Both are great. However I was under the impression that LPR 35 left less black residue on the pinch roller.

Speaking of oxide or back coating residue, on the first run, both tapes left slight traces of dirt on the pinch roller. But nothing on the heads and tape guides. It is kind of expected though. The old Maxell tapes leave zero residue but unfortunately they are well used and are well beyond their usable life by now.

One thing I absolutely love about these new tapes is the fact that on fast rewind or fast forward, the tape rolls up perfectly. It looks like the tape was slowly winded in play mode.

When I will have money I'll buy some other RTM tapes. Maybe I will sell one of the cassette decks to buy a couple of tapes.

If you will

Please note that all the work presented herein this site is non-commercial. This is my hobby and I am doing this in my spare time. Through this page I freely share my knowledge with you. But if you like my work, please consider helping me buy a transistor or a capacitor for my projects.

Thank you!

Copyright © 1998- Alexandru Groza