ADCOM GFA-585 Is it possible for it not to blow up

mobay

Member
2008-01-30 8:10 pm
I bought recently a used ADCOM GFA-585 amp. I've had no issues with it whatsoever. However I learned yesterday that I may have a time bomb on my hands. By that I mean the famous GFA-585 leaking cap issue.

Mine has a serial number of 0463 ( early model I guess ) .

My question is to the experts here:

1) was the failure rate 100% on these amps ?( i.e. just a matter of time )

2) are there any warning signs to show imminent failure?.

3) Could the unit have had the caps replaced by the previous owner ?( what should I look for if I take off the cover?)

Thanks for your patience.

Randy
 

ben62670

Member
2006-12-27 7:58 am
Hey Randy.
I would definetely take off the cover, and change those caps.
Once they leak on the input boards you have major problems. I know. I have about 80hrs between research, and work on mine.
Feel free to contact me. Phone is a lot easier than PM's Also check your DC offset.


Ben
 

mobay

Member
2008-01-30 8:10 pm
I plan to and hope beyond hope that I do not see ELNA caps.. although I kind of doubt it. With me delivering it , the authorised ADCOM service center in Virginia will charge about $230 for the "repair"

If it was'nt for the damn bias adjustment and just a straight cap replacement I'd tackle it myself, I have limited experience or equipment for diagnostic work however. Wrote ADCOM who sent me a detailed .PDF describing the condition ( mainly geared to a 565 mono block) . They basically were VERY helpful in telling me that a problem existed.

I cannot believe that the 565 and 585 could have such a defect and that the failure rate is 100%. Unbelievable.

Once again, mine works perfectly, no thump, no crackling, nothing.., which makes it all the more annoying to have to shell out almost what I paid for the amp ( $300 ) to repair it.

Oh well..., lemme stop whining. Somewhere , somehow there's a person out there with one that has never failed. I'm led to believe by others however, that a scenario like that is like finding a 24 year old virgin in New York or Los Angeles!!

Thanks for the offer, I appreciated it
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi mobay,
Yes, 100%. Sorry to confirm that.

Right now it's a straight capacitor change unless you smell something nasty while desoldering the old parts. Replace all the caps on the board. I am wishing you luck on this.

Would you do me a big favour please mobay? I have not seen the document you are talking about. Is it possible to email it to me? I'll send you my email address.

BTW, the caps are a good brand, but there was a run of bad ones. The electrolyte is the problem. Elna caps are a top brand of capacitor.

Also, I have seen units that have not failed - yet. It might be a temperature related thing. Don't guess, just get it looked after.

-Chris
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi mobay,
I do, and thank you.

I feel that PDF is not entirely accurate and have commented to tech support at Adcom. You have my concerns via my rely to the email. Use your common sense would be my main comment.

The PDF states that those PCBs are "paper", or phenolic type. This is not true, it is an epoxy PCB. It does seem to soak up this evil stuff though. Also, atmospheric contaminants were blamed for the leakage. This is also not the case if you think about it. My belief is that it is an electrolyte issue, the same one that plagued computer products. Elna is a good brand of capacitor normally.

The other comments are easily figured out if you read and look where they are coming from. The Ebayer's comments are a bit self serving and designed to elevate the service above normal attempts. While the service is good as stated, there is excessive work being done and some parts being replaced under the guise of improving the performance. This is also not the case. The original components used are very good. No improvement will be heard or measured with these "upgrades". The flake factor has surfaced.

-Chris
 

mobay

Member
2008-01-30 8:10 pm
The .PDF file on leaking Caps for ADCOM GFA-585

Chris,

As is usual for you , your providing a great service for those of us who own a ADCOM GFA-565 , 585 or maybe even more.

The .PDF file was sent to me by a "sales Engineer" ( yep! that was his title ) at ADCOM's headquarters in AZ. This was after I asked them if the problem was a case of 100% failure of all the units made or just a few. His "help" was to attach the .pdf and then suggest that I get the unit fixed.

I also asked if there were any warning signs to indicate imminent failure , and did not get anything from this " Engineer"

Now a lot of readers will say " why bring up this dead horse"? Well..., a lot of people will get these amps hook them up to expensive speakers , and then have the amp burn them out or God forbid even worse ( fire ). When I bought my amp, I had no idea that there was such a serious and devastating problem.

I know that what I'll say next will not make me popular with ADCOM owners, but just like car manufacturers , ADCOM needs to "fess up" and assume SOME sort of responsibility for this.

My son's 1997 Chrysler Sebring got warranty work done (10 years later ) on a lower control arm for a problem that was discovered a lont time ago. If I had a pair of expensive speakers burnt out because of a amplifier with a known ( by the MFG) defect , you can bet I'll be pissed off.

I still need to know what are the warning signs or will the caps just shoot their wad over the circuit board , and then "whammo!
your speakers are toast!"

Anyone have any real life experiences to relate with this problem, as far as how bad it got for them?

thanks
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi Randy,
Most often there are no warning signs that anyone would notice. Sometimes there may be some low frequency noise, or some excessive on / off thumps. The problem is that it's not until complete failure, or truly excessive offset occurs that the average person would stop using the equipment. That is human nature (from my own observations over the years).

Since Adcom was purchased and completely restructured, I would not expect them to warranty any old products for any problems. I'm just happy they didn't go "poof!" gone. The other issue is that this fault is not Adcom's fault at all. They purchased good quality capacitors and used them properly. It is not a design flaw, nor is it the result of buying from the cheapest vendor. The damage is the result (from what I can tell) of a dishonest company that sold defective electrolyte for use in capacitor manufacture. Perhaps Elna was remiss in it's supply chain management. The current Adcom company had no knowledge or warning of the previous events and is really a completely different company.

I'm not really trying to defend Adcom, but I had a working relationship with the original firm and I knew what their intentions and design direction was. Believe me when I say that this would have been horrifying to them. Completely unavoidable and unintentional. I also know that this information doesn't help you, except that it is now the devil you know rather than a surprise speaker cook-off. :devilr:

-Chris
 

mobay

Member
2008-01-30 8:10 pm
OK Chris will lay this one to rest

No need to waste electrons. I'll just have to bite the bullet and send the unit to be fixed. Wish I could have simply replaced the capacitors as that does not look too hard.

But, if I have to then do diagnostic work afterwards, I cannot
take the chance of blowing the amp up.

Thanks again Chris
Randy
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi Randy,
Why not have a look? If the caps have not leaked yet, you should be able to do the job.

-Chris

Edit: Look for soggy bottoms on the caps. If you touch the bottom with your hot soldering iron, you can sample the odor to you can test the PCB. IF all you smell is hot rubber - GREAT!!!
 
The other thing that can be checked, without opening the case, is to look for signs of DC offest at the speaker terminals (with the inputs & speakers disconnected).

In a healthy amp, any DC seen at switch-on should rapidly decrease toward zero, and be well within single digit millivolt levels after the amp has reached thermal equilibrium. Larger offsets, certainly at the level of 0.1V or greater could indicate a problem.

Check both channels and compare, if you are able. My amp had one good channel and the other with a catastrophic 71V offset. Both channels had leaky capacitors, but after removal, thorough board cleaning and reassembly with new caps the amp operates beautifully. More details on this repair here http://www.diyaudio.com/forums/showthread.php?s=&threadid=90059

The time consuming work is in extracting the boards, keeping proper tabs on the many connecting wires, some soldered, some with plugs/sockets.


The usual caveats about extreme caution, only making connections with the power off, guarding against short circuits etc apply when testing.

Ed
 

mobay

Member
2008-01-30 8:10 pm
OK so if the caps are not leaking , a replacement can be done easily

So, if I find not leakage of the caps ( possible ) and I replace ALL of them with newer caps, would one have to do any detailed bias adjusting or anything that is specialized?

I would replace every cap on the board. Could one then fire up the amp or is this just a pipe dream.?

Sorry for not ending this but I need to know.
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi Randy,
Replacing capacitors only should not require any adjustments at all. When I pull bias pots to clean them, I keep track of which is which. Normally the bias is exactly where it was before I start the job.

So, in a nutshell, you should not need to do anything more than replace the capacitors if there is no leakage.

Hi Ed,
Pretty much. Most home owners do not own a meter, or know how to use one.

-Chris