Adcom GFA-585 Limited Edition Repair

[anatech]

Hi All,
Is there anyone close to Fearlessleader1 that can give him a hand??

There has to be someone!

-Chris

 

[K-amps]

Or an authorized warranty depot. A good one. It is unlikely that there is no sub for your caps. The leakage should be visible on the board, but I haven't heard of this as a specific fault or weakness. It is possible.

Too bad I'm in Canada, shipping is a supreme pain (border thing).

-Chris

Chris,

If you can slip pass the border, I have a 585 and a 565 that need repairs, I never had the time to dabble with them ... seriously




Wilson, If I were you , I'd send the amp to Anatech prepaid and not worry about it. He knows more about the Adcoms than probably any tech you could send it to locally.

 

[Fearlessleader1]

murphy,anatech

I have been in contact with the repair sevice and he is going to try the dishwasher trick I hope this works when I hear from him I will let you all know. I am very grateful for all your help. I know I am not out of the woods yet but at least I have the stars to guide me.

THANKS

 

[anatech]

Hi Arif,
I can't live up to that claim, but thanks. There are many techs out there who are just as talented for sure. Just got to find them.

No problem looking at your amps, I just don't get out much at the moment. Might be nice to take another trip through the 'States some year. I've driven to Florida and North Carolina, plus some short trips into New York. I would have to pay duty to get the amps across the border in my trunk though. Then they still have to come back.

-Chris

 

[anatech]

Hi Fearlessleader1,
It's very important they remove the bias control first. You do not want to wash that! I wish you luck with them. I hope they use some common sense.

-Chris

 

[K-amps]

Actually Chris,

I may just convert them into class-AB krell klones running at 95vdc rails. Using the KSA-50 boards. Will add a CCS to the front end to take the high voltage.

Both the 585 and the 565 have the same chassis so I could get a pair of amps out of them...

 

[anatech]

Hi Arif,
True, but the front panels will lie! Kind of a shame really. Adcoms aren't bad and have resale value.

Now if you were to strip some old 4B's - GREAT! I couldn't think of a better use of those chassis's. Besides, they are well out of warranty now.

-Chris

 

[Kmh3212]

Me Too!

I bought my GFA 585 a year or so ago hooked it up to a pair of 'tester' speakers and got a loud thump but it sounded okay. I turned it off and again a loud thump. I knew it was probably needed a cap job. Well it got pushed aside for other projects and I hooked the speakers back up for another test before I popped the hood. Bad noise, very bad noise. I couldn't pull the plug out fast enough blew a fuse. I did a quick visual and replaced all the E-caps on the left and right boards. Oh I cleaned the boards up with warm water and a little dish soap and a soft tooth brush. These caps had leaked terribly. Black smelly goo. I put the caps in and checked the boards for continuity where the goo was eating the traces. It was fine. Put the boards in. Found out the voltage on right channel was -85 volts. That speaker was toast of course. The left was a +1 volt. But the left speaker was toast as well. I pulled the boards and somehow I missed cleaning the right board where the support bar was hiding q160 and q161 and the r142 and r143. Started ordering parts... at myself.

 

[anatech]

Hi Kmh3212,
Did you remove the parts in that area before cleaning the board? If not, guess what? You also need to clean or replace the parts in those areas. There is no short-cut for this.

Measure your output DC offsets without connecting a load.

-Chris

 

[Kmh3212]

I was very careful and wiped with a damp paper towel just on that corner and and used very little water. The electrolyte dissolved easily and used the soft brush gently and wiped after each time. It only took a couple minutes the only component that got a little wet was a two legged q102 one leg was corroded off. q162 really wasn't involved. Nothing else got wet well except the resistor next to the transistor and it was going to get replaced anyway. One of its legs was corroded.
I read the dishwasher idea and I know the that that type of soap is very alkaline and very aggressive. Of course that electrolyte must have been a little acidic to corrode the transistor leg away and the tracings on the board.
A little dawn in warm water is pretty harmless and I was careful.
I know what happened the phone started ringing while I was in the middle of cleaning and that corner on that and that side just got missed.
I wish that I would have fixed the amp when I first got it.

 

[Kmh3212]

I will let you know how it turns out.
Thanks Kevin

 

[KD6AR]

Bad news. You have a lot bigger job than you signed on for. The electrolyte is insidious. It's under the traces, under the conformal coating. Extremely hard to totally get rid of. This come from personal experience. You think you got it all, then months later more electrolyte starts seeping from under the traces. You get the idea.

Has anyone just created a replacement PCB? That would be a much better solution than trying to rehab a contaminated board.

I will let you know how it turns out.
Thanks Kevin

 

[Kmh3212]

I was beginning to desolder the trashed caps and this bubbling was going on and it was the black stinky goo was boiling out of the hole in the solder trace. Yes this problem might come back to haunt me. It seems that it was just the four caps on the corners of the boards. The cap in the center did not appear to be leaking but it's gone now.
Question for those who made this repair before me did you replace the little e-caps on the amp boards? Any leakage from those? I will because they cheap and easy to get to.

Thanks gentleman for the help!
Kevin H.

 

[Kmh3212]

On second thought I am replacing all the Electrolytic caps in the amp. I also found a transistor with only 2 legs left several of the others around it had corrosion on the legs and a resistor burned open. I am still on it as the parts trickle in.
Kevin