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

AKAI AA-5210 #2: Introduction

This is one of my two identical amplifiers that I use in my study.

The electrical characteristics of this small amplifier might look conservative at first. But I assure you, it is a true performer. This amplifier came to me with the front face clogged with cigarette smoke. It had a dark golden hue. I tried to wash it as much as I could. Unfortunately some of the letters in the POWER inscription got wiped. Inside it was like new. But the cigarette smoke is omnipresent. This amplifier requires a thorough cleaning of the circuit boards. This could only mean complete strip down of every electronic part. The volume button interrupts a little at about a third of its course. A faint electrolyte smell mixes with the cigarette smoke. Otherwise, it still sings music. And does it well enough for its age.

If you want to see its brother passing through the same restoration process, then check out its page: AKAI AA-5210 #1.

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

AKAI AA-5210 #2: Technical Data

This amplifier has the following technical characteristics.

TECHNICAL PARAMETERS
ParameterValue
Continuous RMS power (both channels)15 W + 15 W (8 Ω at 1,000 Hz)
Total Harmonic Distortion<0.5% (at rated output)
IHF power bandwidth (each channel driven at 8 Ω)15 Hz - 80,000 Hz
Frequency Response (at normal listening level)20 Hz - 50,000 Hz
Load Impedance4 Ω - 16 Ω
SemiconductorsTransistors: 23 / Diodes: 8
Power Voltage100 V, 117 V, 220 V, 240 V, at 50/60 Hz
Power Consumption120 W (max)
Dimensions / Weight108 mm (H), 430 mm (W), 290 mm (D) / 7.2 kg

Article #3 | 12:00 PM Tuesday 05/01/2016

AKAI AA-5210 #2: Parts List

I have assembled a parts list for this amplifier. My restoration touches some of the original transistors. Normally the original transistors contribute to the authentic AKAI sound. But modern equivalents are better in any aspects. I am also 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. 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

The Power Amplifier Block is coded 96-5008 and is located in the bottom-right part of the steel chassis. You will recognize it by the power transistors which are mounted on an aluminum radiator.

Power Amplifier Block (96-5008)
IdentifierSchematicRecommended
1-C12.2 uF / 50 V
1-C1b2.2 uF / 50 V
1-C2100 uF / 50 V
1-C2b100 uF / 50 V
1-C52.2 uF / 80 V
1-C5b2.2 uF / 80 V
1-C7100 uF / 6.3 V100 uF / 16 V
1-C7b100 uF / 6.3 V100 uF / 16 V
1-C91000 uF / 25 V AUDIO
1-C9b1000 uF / 25 V AUDIO
1-C11220 uF / 35 V
1-C11b220 uF / 35 V

The Tone Control Block is coded A5-5029 and is located in the front-center region of the steel chassis, next to the tone shaping potentiometers. For an easy maintenance access, you need to extract this board. Or you could work your way through the bottom of the amplifier chassis after you remove the switches printed circuit board.

Tone Control Block (A5-5029)
IdentifierSchematicRecommended
2-C147 uF / 50 V
2-C1b47 uF / 50 V
2-C547 uF / 6.3 V47 uF / 25 V
2-C5b47 uF / 6.3 V47 uF / 25 V
2-C64.7 uF / 25 V4.7 uF / 50V
2-C6b4.7 uF / 25 V4.7 uF / 50V
2-C1010 uF / 25 V10 uF / 50 V
2-C10b10 uF / 25 V10 uF / 50 V
2-C12100 uF / 6.3 V100 uF / 25 V
2-C12b100 uF / 6.3 V100 uF / 25 V
2-C1347 uF / 50 V
2-C13b47 uF / 50 V
1-C142.2 uF / 25 V
1-C14b2.2 uF / 25 V

The Equalizer Block is coded A5-5028 and implements the Phono preamplifier and the RIAA correction curve. You can find it in the front-right part of the steel chassis, next to the Tone Control Block board. In order to operate changes, you need to extract this board too. Or you could work your way through the bottom of the amplifier chassis.

On this board the capacitors are listed for both channels.

Equalizer Block (A5-5028)
IdentifierSchematicRecommended
3-C1100 uF / 16 V100 uF / 25 V
3-C2100 uF / 16 V100 uF / 25 V
3-C31 uF / 25 V1 uF / 50 V FILM
3-C41 uF / 25 V1 uF / 50 V FILM
3-C52.2 uF / 25 V
3-C62.2 uF / 25 V
3-C710 uF / 25 V10 uF / 50 V
3-C810 uF / 25 V10 uF / 50 V
3-C91 uF / 50 V1 uF / 50 V FILM
3-C101 uF / 50 V1 uF / 50 V FILM

The Power Supply Block is coded A5-5026 and occupies the bottom-center of the steel chassis next to the power transformer. You recognize it by the four rectifier diodes.

For the electrolytic capacitors on this board, you need to order only once.

Power Supply Block (A5-5026)
IdentifierSchematicRecommended
5-C1100 uF / 63 V100 uF / 100 V
5-C2330 uF / 63 V470 uF / 100 V
5-C3330 uF / 63 V470 uF / 100 V
5-C447 uF / 50 V47 uF / 63 V

The construction of this amplifier is straightforward and poses no problems for the restoration.

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 | 10:00 AM Monday 06/01/2018

AKAI AA-5210 #2: Restoration

I have already restored it's sibling which means that I already have the restoration plan in my mind. Everything should be straightforward.

I am not going to repeat myself regarding part numbers and replacement component markings. In short I have used the exact same parts as for the first AKAI AA-5210 that I have been working on.

General Considerations

I should begin by saying that working on this amplifier 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 amplifier, 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 exactly 323 degrees Celsius is sane for these vintage printed circuit boards. 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. While working on the chassis, I am pumping up between 360 and 440 degrees Celsius in the soldering iron.

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

Here are some before and after pictures of this unit.

96-5008 Power Amplifier Board Restoration

Here is the board before the job.

And here it is after servicing.

A5-5029 Tone Control Board Restoration

This is the board before the service operation.

And here it is after servicing.

A5-5028 Equalizer Board Restoration

Here is the board before the job.

And here is the board after working on it. Note the transistors mounted in reverse. This is due to the modern parts having mirrored terminal disposition.

A5-5026 Power Supply Board Restoration

Here is the board prior to restoration.

And after the job.

This concludes the restoration of this unit.

Article #5 | 01:42 PM Monday 19/02/2018

AKAI AA-5210 #2: Impressions

So how does it sound? Like it's twin brother. I parted with this amplifier because it was accumulating dust. And a superb little amplifier like this should be singing music. Not waiting in the corner. It is still in the family though. My wife's brother in law has it these days.

Overall I declare the restoration a success.

Copyright © 1998- Alexandru Groza