Accuphase M-60 Love

[User211]

Sussed it. The yellow ITT cap is fine I was pretty sure I had tested all the caps. It's the 4.7uF soft start cap. The two transistors below it - one is definitely knackered the collector / emitter is not open circuit, which it should be. The other one is fine.

These two transistors control the relay state depending on the cap charge state.

Degree of certainty is very high I would say. Probably a good idea to do all the transistors on the board in one go.

I spoke to two electronics repair guys and they would not touch this amp despite trying to talk them into it.

Fault finding this really didn't prove difficult, so their loss I guess.

[Macca]

I wonder what sort of repairs they will do?

I mean it's an old amp, you have the schematic, there's no surface mount, it's all neat and tidy. Is there some reason I don't know?

[User211]

They were both Weston-super-mare based.

One guy wouldn't touch it because it was high end and it weighed too much. He did sound pretty old, though.

I'm struggling to remember the other phone call, but I know it was the second time I had called him (the other was for the 211 amp fault) only to be turned away again.

I could have tried Alan (Firebottle) but I just decided to get into DIY figuring it'd be cool to sort stuff out myself.

There's a high likelihood more failures will occur with the M-60s and I just don't want to sell them. So it's probably a good decision long term.

[Macca]

Makes sense. I wouldn't have the courage.

[Swann36]

I wonder what sort of repairs they will do?

I mean it's an old amp, you have the schematic, there's no surface mount, it's all neat and tidy. Is there some reason I don't know?

Point well made

[Firebottle]

You're doing brilliantly Justin, well done.

[User211]

Thanks, Alan

To make it clear to others the resistors that were failing are only designed to take strain until the relay clicks after 3 seconds. Cos it never does they get more than they can handle, so 10W or 20W ones will fail. A cheap fail-safe in a way, I guess.

[User211]

Ordered some bits. These suckers are definitely not dying on my watch.

[User211]

Been looking at an Accuphase DF-75 active crossover. One on eBay for 6K. I reckon I can build one with an 8 inch OLED to control various parameters with a Raspberry Pi 5, plus some A/D, DSP and D/A boards.

Most of the time will probably be spent writing the GUI.

Cost probably £1K and absolutely bespoke to my needs. Performance probably close to the Accuphase.

Finding the time is another matter.

[User211]

OK whilst I think that protection board is knackered as described and I now have the parts to fix it, I thought let's put the protection board in from the working amp with a new 20W resistor.

Result? The resistor blew again.

The relay the protection board controls is this one, and it clicks almost insanely loudly 3 seconds after power up in a working amp.