Introduction

This is was 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.

Technical Data

This amplifier has the following technical characteristics.

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. I don't believe that transistors actually contribute to any specific sound signature. 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.

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.

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.

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.

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

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

Working on this unit exposes you to electrical hazards. There are lethal voltages inside.
Severe accidents and possibly death by electrocution might occur. I am qualified and skilled at electronics and I have been doing audio gear repairs for over 20 years. If you lack experience, please take these articles as just a knowledge base. Do not attempt to repair something that you cannot handle as there is a high chance of doing further damage while also possibly suffering accidents.

Good tools are a must for a quality restoration. I use eutectic soldering alloy and a temperature-controlled soldering station equipped with various tip shapes. I have both standard and precision desoldering pumps and desoldering wicks of various widths. To clean the flux, I use isopropyl alcohol and high-purity acetone.

Empirically, I found that soldering at a temperature of exactly 300 °C is safe for these vintage printed circuit boards. I have never lifted any pads and I never wait more than a couple of seconds with the hot tip on any pad. While working on the chassis, I use between 360 and 440 °C. Flux fumes are extremely toxic and should be avoided at all costs.

Every replacement part is brand new, from a reputable manufacturer, ordered from the U.S.A., Japan, or Germany. In addition, I only use parts that are suitable for specific circuit sections, after inspecting and comprehending the original schematic diagrams. Last but not least, I have years of experience backing up my choices and actions.

Sometimes, I like to take unnecessary actions, such as replacing perfectly working components for futureproofing, or completely stripping down PCBs of parts for a better cleaning. While tedious, I have fun while doing so, and I also learn a thing or two in the process.

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.

Impressions

So how does it sound? Like its twin brother.

In the end I parted ways with this amplifier once the Sansui AU-7500 took over my dual amplification rig in my study. In addition, a superb little amplifier like the AA-5210 should be playing music instead of waiting in a corner. It is still in the family, though. These days, my wife's brother in law owns it.

But overall, I declare the restoration a success.

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

Thank you!