Vintage Audio
this section covers some restoration work that I did on my vintage HI-FI gear
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Article #1 | 10:00 PM Sunday 03/01/2016

Sansui AU-666: Introduction

This is my wife's amplifier.

Article #2 | 11:00 PM Sunday 03/01/2016

Sansui AU-666: Technical Data

This amplifier has the following technical characteristics.

TECHNICAL PARAMETERS
ParameterValue
Continuous RMS power (both channels)35 W + 35 W (8 Ω at 1,000 Hz)
Total Harmonic Distortion<0.5% (at rated output)
Intermodulation Distortion (60 Hz : 7,000 Hz = 4:1 SMPTE method)<0.5% (at rated output)
IHF power bandwidth (each channel driven at 8 Ω)10 Hz - 40,000 Hz
Frequency Response (at normal listening level)10 Hz - 40,000 Hz ±1 dB
Load Impedance4 Ω - 16 Ω
Damping Factorapproximately 40 at 8 Ω load
SemiconductorsTransistors: 33 / Diodes: 13 / S.C.R.: 2
Power Voltage100 V, 110 V, 117 V, 127 V, 220 V, 230 V, 240 V, 250 V at 50/60 Hz
Power Consumption240 W (max)
Dimensions / Weight127 mm (H), 415 mm (W), 278 mm (D) / 9.75 kg

Article #3 | 02:58 PM Tuesday 05/01/2016

Sansui AU-666: Parts List

I have assembled a parts list for this amplifier. My restoration does not touch original transistors as I consider them irreplaceable for an authentic Sansui sound. Thus I am only interested in exchanging the electrolytic capacitors. So this is what you will find listed below.

The schematic value corresponds to what normally can be found in the electrical schematics. The recommended value is what I replaced the former part with. The BP inscription signifies a bipolar capacitor. Where I found appropriate, I have chosen a film capacitor replacement instead of an electrolytic. My reasons are reliability in time. Less electrolytic capacitors, less time-ticking bombs.

Descriptions and Parts Listings

There are some Power Supply electrolytic capacitors mounted directly on the steel Chassis. These are either filter or decoupling capacitors. Normally I don't recommend replacing the big filter capacitors. Should they test OK, leave them alone. Otherwise, get replacements. But the smaller ones need to go.

Power Supply / Chassis
IdentifierSchematicRecommended
C0023300 uF / 50 V
C0033300 uF / 50 V
C9051 uF / 50 V1 uF / 50 V FILM
C9061 uF / 50 V1 uF / 50 V FILM
C9072.2 uF / 50 V2.2 uF / 63 V
C9082.2 uF / 50 V2.2 uF / 63 V
C9091 uF / 50 V1 uF / 50 V FILM
C9101 uF / 50 V1 uF / 50 V FILM

There are two Driver Block boards in this amplifier. They are coded as F-1159A. These boards are positioned in front of the big black power transistor aluminum radiator. They are socketed in blue sockets mounted on the chassis. In the table below, I have listed the electrolytic capacitors for only one board. So be careful to double order each part. Thankfully, on this board, the engineers have spared electrolytic capacitors in favor of Mylar film ones. I cannot but greet them! Thank you, Sansui!

Driver Block (F-1159A)
IdentifierSchematicRecommended
C80747 uF / 10 V BP47 uF / 16 V BP
C809100 uF / 10 V100 uF / 16 V

The Minus Ripple Filter Block board is mounted under the steel chassis, near the big filter capacitors. It is coded as F-1277A. Easy to spot, even easier to operate changes.

Minus Ripple Filter Block (F-1277A)
IdentifierSchematicRecommended
C814100 uF / 50 V100 uF / 63 V
C8164.7 uF / 50 V4.7 uF / 63 V

The Plus Ripple Filter Block board is mounted under the steel chassis, left of the Minus Ripple Filter Block board. It is coded as F-1231A. Easy to spot, even easier to operate changes.

Plus Ripple Filter Block (F-1231A)
IdentifierSchematicRecommended
C813100 uF / 50 V100 uF / 63 V
C8154.7 uF / 50 V4.7 uF / 63 V

The Tone Control Block board is coded F-1279 and is mounted upside down in front-left of the amplifier chassis. It is held in place by the potentiometer axles. In order to remove it, you need to undo the potentiometer axle nuts. I recommend to get it out in order to gain better access to it.

Tone Control Block (F-1279)
IdentifierSchematicRecommended
C70510 uF / 10 V10 uF / 16 V
C70610 uF / 10 V10 uF / 16 V
C70747 uF / 6.3 V47 uF / 16 V
C70847 uF / 6.3 V47 uF / 16 V
C70910 uF / 25 V10 uF / 50 V
C71010 uF / 25 V10 uF / 50 V
C72147 uF / 6.3 V47 uF / 16 V
C72247 uF / 6.3 V47 uF / 16 V
C72310 uF / 25 V10 uF / 50 V
C72410 uF / 25 V10 uF / 50 V
C7251 uF / 50 V1 uF / 50 V FILM
C7261 uF / 50 V1 uF / 50 V FILM

The Speaker Protector Block board is coded as F-1234 and is mounted under the steel chassis, just above the two blue sockets for the Driver Block boards. If we take the blue sockets as a reference point, then the Speaker Protector Block is diametrically opposing the Minus and Plus Ripple Filter Block boards. Easy to spot, even easier to operate changes.

Speaker Protector Block (F-1334)
IdentifierSchematicRecommended
C903220 uF / 10 V BP220 uF / 16 V BP

The Ripple Filter Block board is coded as F-1268A and is mounted below the mains transformer, in the left region on the steel chassis. This board does not require removal in order to exchange parts. The solder side is accessed from below.

Ripple Filter Block (F-1268A)
IdentifierSchematicRecommended
C012100 uF / 50 V100 uF / 63 V
C013220 uF / 50 V220 uF / 63 V
C014100 uF / 50 V100 uF / 63 V

The Head Amplifier Block board is coded as F-1284-1 and is socketed in the far front-right region of the steel chassis. You cannot miss it.

Head Amplifier Block (F-1284-1)
IdentifierSchematicRecommended
C60547 uF / 6.3 V47 uF / 16 V
C60647 uF / 6.3 V47 uF / 16 V
C607100 uF / 6.3 V100 uF / 16 V
C608100 uF / 6.3 V100 uF / 16 V
C61110 uF / 25 V10 uF / 50 V
C61210 uF / 25 V10 uF / 50 V
C62133 uF / 16 V33 uF / 25 V
C62333 uF / 6.3 V33 uF / 16 V
C62433 uF / 6.3 V33 uF / 16 V

A lot of capacitors, indeed. But no need to worry. Take one board at a time. Success is guaranteed.

As always, let me throw a piece of advice. Do not hurry, take your time and do the job once. And do it well.

Article #4 | 02:31 PM Wednesday 27/01/2016

Sansui AU-666: Woodwork

I started by restoring the wooden case. As you would have expected, it is crafted from real wood with a walnut (?) wooden veneer applied on top. I find it beautiful but it has a few scratches and usage marks here and there. Here are a few pictures of what the case looked before the restoration.

This is the underside of the wooden case. You can see the real wood grain. In my opinion, it is beautiful on the inside too.

To restore this part, I first opted for a thorough rubbing alcohol cleanup on the entire veneer. It came up pretty good. Then I used some felt to even up the surface and remove minor imperfections. Deep scratches, however are here to stay. I don't have means nor skills to restore them. Then I took some walnut wood stain that I applied with a soft sponge brush. After the first coat, it looks like this.

Or, in daylight it appears like this.

A second and final coat of walnut stain produced this end result. Before applying this final coat, I have slightly sanded the case with my trusty felt. Light scrubbing with alcohol helped remove the dust. Don't insist as stain is easily removed by sanding or alcohol rubbing.

This is all I am going to do to this case. I think it's current condition nuances the fact that this amplifier is over four decades old and adds to the appealing aging wood character. A little secret I wanted to share: in time, I have learned to like imperfection. Anyway, should I ever put my hands on a nice piece of oak or walnut wood, I would very much like to find a workshop to build a replica of the original case. I would not use veneer but wood stain and lacquer instead. It might be a nice future project.

But for now, let's continue with the next stage.

Article #5 | 10:00 AM Saturday 30/01/2016

Sansui AU-666: Cleaning the Dirt

Before moving on to electronics, I have decided to clean the internals and the front mask and knobs.

Stay tuned as pictures are on their way.

Copyright © 1998- Alexandru Groza