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Musical Fidelity A3 Integrated Amplifier Corrosion Repair

This Musical Fidelity A3 Integrated Amplifier suffered from something worse than the usual cheap parts – a leaking Varta NiMH battery.

I really appreciated the feedback I received about the Sansui AU-D707 article and I know how much people enjoy these articles so here’s another one for your reading pleasure.

We all know that you shouldn’t leave batteries installed in equipment for long periods of time because they leak, right? Well, do you know what happens when a manufacturer solders in a ‘permanently installed’ nickel-metal-hydride or NiMH battery that nobody knows they should check? In the case of the Musical Fidelity A3 integrated amplifier, this is what happens:

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No kidding, this is dire and a potential amplifier killer, because replacement boards are no longer available. I know that this fault has written off other A3s and I wonder how many people reading this have equipment like this, containing memory batteries that have never been checked? Hopefully, this serves as a reminder to have equipment inspected and serviced periodically, whatever it might be. Batteries can destroy electronic equipment.

UPDATE: Can you believe this article and video have already saved several people’s amplifiers from certain death?! Hopefully we save a few more!

I’ve written quite extensively about Musical Fidelity equipment (and owned a few pieces), including my favourite Tri-Vista 21 Class-A Tube DAC with multiple articles and videos, the M1 DAC, the beastly NuVista M3 Amplifier, and more.

As usual, check out our video summary with other details:

Features

The Musical Fidelity A3 Dual Mono integrated amplifier is a basic, solidly built, UK made integrated amplifier with op-amp based phono preamp and a selection of fairly ordinary parts, including the not very nice SAP15N and SAP15P Darlington pair output devices that fail and can not be replaced because they are no longer available.

Musical Fidelity A3 integrated amplifier
The Musical Fidelity A3 integrated amplifier is a handsome amp to many. Personally, I prefer the silver highlights of the A3.2 series, which I think is one of the best looking series of modern hi-fi gear.

Why were these devices used? This will explain why: each device contains two transistors, an emitter resistor, a diode and some other stuff, depending on polarity. It’s like a big op-amp. These save money and allow for a simpler more cost-effective layout, just like the op-amp they use in the phono preamp does.

Musical Fidelity had a habit of buying up big on a certain part type and I’m guessing they did that with these SAP15s as they are used in many of their products from the time. When they fail, and they do for thermal reasons and because you can’t make a big resistor and several transistors and diodes fit into a little plastic package and handle any power, they cannot be replaced. Something else must be used and boards modified accordingly and with an amplifier like this, that may not be worth doing.

Other than that, they are a well-built amplifier, with two decent sized toroidal transformers, nice heatsinks and good quality boards. Significant improvements can be made to these and everything else MF makes, simply by focussing on parts.

Musical Fidelity A3 integrated amplifier
OK so this is the inside AFTER repair, but don’t worry about that, it’s here to show the layout. The good: dual mono, toroidal transformers, one-board design with nice silk-screening, minimal wiring, serviceability. The bad: puny C-grade filter caps, op-amp phono pre and SAP15 output devices, Teapo capacitors, cheap connectors. Note how the board used here has provision for two extra output devices per channel. A more expensive model would have used the same board, with extra devices.

Musical Fidelity A3 Specifications

Courtesy of HiFi Engine

Power output: 85 watts per channel into 8Ω (stereo)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.008%
Input sensitivity: 0.35mV (MC), 3.5mV (MM), 300mV (line)
Signal to noise ratio: 72dB (MC), 80dB (MM), 96dB (line)
Dimensions: 440 x 95 x 400mm
Weight: 13kg

Issues

I have a real love-hate relationship with Musical Fidelity because they made some great sounding gear and found a unique niche design-wise. But they just won’t stop using crappy C-grade parts, and cheesy plastic connectors. The modern stuff is worse too. My feeling is to try to improve the MF gear you own, if you like it, or sell it and buy better if you don’t.

This Musical Fidelity A3 integrated amplifier presented with some obvious functional issues, and more that I found internally:

  • Source selection buttons had a mind of their own
  • Some buttons didn’t work
  • Power on LED not working
  • Obvious and horrendous Varta NiMH battery leakage corrosion, board, connector and LED damage

Corrosion and board damage this severe could easily write off an amplifier like this, especially as replacement boards are no longer available. In this case, I suggested to the owner that we have a crack at removing, detoxing and repairing the board. He agreed.

Repair

In any case like this, we start with disassembly and cleaning. This necessitated the removal of the volume knob, front panel assembly and control board. Once done, I could focus on cleaning and repairing the control board.

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Musical Fidelity A3 integrated amplifier
We thoroughly cleaned the front panel – this is before cleaning.
Musical Fidelity A3 integrated amplifier
This is truly awful, one of the worst cases of board corrosion I’ve seen. The timely removal of that battery would have prevented this. Note the way the battery electrolyte follows traces and pads, and then wicks along wiring, including the connector I had to cut the wires to, and the power-on LED, which died from the effects of the electrolyte.
Musical Fidelity A3 integrated amplifier
The dead NiMH battery must be removed, and not replaced in this case.
Musical Fidelity A3 integrated amplifier
Note the damage to the front side of the same board. The corrosion must be removed.
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A lot has happened between the previous photo and this one: a detergent and water board wash and scrub, a vinegar wash and scrub, a distilled water rinse, time in the drying oven, and a glass fibre pen scrub to remove the surface corrosion, where possible.
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More work on the front of the board and I replaced the small electrolytic cap near the controller. The board will never look new, but the corrosion source is gone.

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Loose surface corrosion gone, many joints re-worked, extension wires attached, trace repair made.

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Ded LED…
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New LED assembly, with current limit resistor inside heat-shrink. This little red panel LED fits perfectly and looks completely original.

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Musical Fidelity A3 integrated amplifier
There she is, repaired and running normally again. Well worth doing I think, given how much MF wants for a new equivalent of this.

Verdict

Well, what a great result. Apart from probably not remembering what source was previously selected (and who really cares about that anyway), this Musical Fidelity A3 integrated amplifier now works perfectly again, much to the surprise and appreciation of her owner.

Musical Fidelity A3 integrated amplifier
Note the beautifully clean front panel in this shot.

She is now spotlessly clean, all LEDs and switches work and the amp is fully functional. The control board has taken some punishment, but the neutralisation cleaning process I use should mean that the corrosion is halted and that the owner can keep enjoying his amplifier rather than having to buy a new one. That’s a win and a good example of the sort of results we work hard to achieve.

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The Musical Fidelity A3 integrated amplifier is an undeniable cool-looking unit.
Musical Fidelity A3 integrated amplifier
I prefer the silver-trimmed A3.2 series, but the Musical Fidelity A3 is a good looking old girl.

Can you believe this article and associated video have already saved several people’s amplifiers from certain death?! If I saved you and your amplifier with this article, you’re welcome, there’s a drink donation button in the footer which helps me continue to create content like this 😉

As always, thanks for reading, get in touch if you’d like Liquid Audio to care for any of your Musical Fidelity equipment and happy hi-fi-ing!

4 thoughts on “Musical Fidelity A3 Integrated Amplifier Corrosion Repair”

  1. timothy joel davis

    Awesome article Mike! I’m starting to believe you have taught enough about electronics over the past 5 years via your articles that I may be ready to start learning electronics repair my own self. In keeping with that line of thought I must ask, do you have any reason to believe that my Musical Fidelity A324 D/A processor could suffer from a similar issue? I’ve had it for over a decade & other than the co-ax input no longer locking onto an input signal, it’s been great. I’ve had it hooked to a JVC transport through the optical input for years with no issues. Also, know this, if it weren’t for the huge round trip shipping cost from Nc, USA to Australia & back I would have packed it up years ago & sent it down to Perth for you to service & hopefully correct it’s one minor issue.

    1. Hi Tim, thank you, sounds like a good plan, go for it! I can’t say if the A324 has the battery, but if it does, it has to be removed. These can be greatly improved too, but you’ll find modern DACs perform better in many cases.

  2. Matthew Davidson

    Really interesting to read this post and the Sansui article. Thanks for taking the time to document things as you go along. Cheers

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