Adcom GFA-585 problems

heiney9

Also for kicks after you put everything back together it would be a good idea to power up and check the DC offset at the speaker terminals with a volt meter (mV) and let it idle for a good 60-90 minutes and check again. That way you won't fry any VC's on any speakers even if they are cheap JVC's. One of the easiest things to check for is large amounts of DC leaking to the speakers.

heiney9

Also those boards are not available from Adcom or anywhere else for that matter. So cleaning them up really well and inspecting for any trace cracks is very important. I've read of people taking blank boards and making their own traces, but that takes a $hitload of patience and know how. So do your best to really clean them up well with a process that doesn't damage the boards.

ben62670

You seem almost as nervous as I am.

heiney9

ben62670 wrote:

You seem almost as nervous as I am.

I just know what a nice amp that is and the fact that it's a limited run and some parts are hard to come by. Just wanted to pass on some info.........:D . There probably isn't anything that can't be fixed some way, but it's much easier and much more cost effective to do it right from the beginning than it is to try and fix a bunch of bad blunders.

If this were a typical inexpensive straight forward design where parts were easily interchangeable and a dime a dozen I'd say go after it with reckless abandon..............but that's not the case here. So caution is the order of the day.

ben62670

Yes sir I fully absolutely 110% appreciate what you are saying. This amp is #1096 out of a run of 2000 or 3000. I forget. The person I purchased this from on ebay said they would give me a full rebate minus the shipping. I didn't want to loose the $100+ round trip on shipping, and risk the amp being damaged even more. So I kept it.

unc2701

ben62670 wrote:

Yes sir I fully absolutely 110% appreciate what you are saying. This amp is #1096 out of a run of 2000 or 3000. I forget. The person I purchased this from on ebay said they would give me a full rebate minus the shipping. I didn't want to loose the $100+ round trip on shipping, and risk the amp being damaged even more. So I kept it.

Well, I feel better knowing that my old one isn't out there **** you over... I had #1580

(In case you're wondering, I still have pics on my computer from where I ebay'd it).

heiney9

unc2701 wrote:

Well, I feel better knowing that my old one isn't out there **** you over... I had #1580

(In case you're wondering, I still have pics on my computer from where I ebay'd it).

It's funny you should say that. My brother has an Adcom GCA-510 which is in my possesion currently and the caps are leaking (seems they are anyways light sticky residue around the 4 caps) and some prior owner has been inside and lost screws and had the output board out because there are large burrs on the brass nuts that attach the wires to the speaker terminals. Apparently he didn't know what he was doing. I think the amp sounds off and my bro is going to sell it and disclose that it might have some issues. I'm still looking for one of these so I am going to copy down the serial number so I don't buy it later down the line.

Someone got into this unit and had no clue what they were doing adn while it might sound fine to most I've had it hooked up several times and it just seems to be a bit off, nothing drastic but it just doesn't sound quite right. If I were to repair it I'd have to buy it from my bro and I'm not interested in paying for it and then sending it for repair.

ben62670

"Someone got into this unit and had no clue what they were doing "
It wasn't me.
I'm about 20 minutes away from firing her up. Not setting her on fire! Are the caps Elna caps? I wouldn't hesitate at all on a preamp. There isn't much juice running through it to hurt much. But... It isn't yours either. Is it wrong to pray for an amp?

fingers crossed and praying Ben

heiney9

ben62670 wrote:

"Someone got into this unit and had no clue what they were doing "
It wasn't me.
I'm about 20 minutes away from firing her up. Not setting her on fire! Are the caps Elna caps? I wouldn't hesitate at all on a preamp. There isn't much juice running through it to hurt much. But... It isn't yours either. Is it wrong to pray for an amp?

fingers crossed and praying Ben

Not Elna caps and the GCA-510 is Adcom's version of an integrated. 50 watts per channel it's a bit odd because the pre-amp section is line stage passive. It's essentially a Gfa 535 with the SLC 505 passive controller in one unit. It's slick but it's not mine and I'm not messing with it.

Good luck and be sure to report back

heiney9

The GCA-510 has over 27,000 uF of filter capacitance so it could give you a good zap if you aren't careful .

H9

ben62670

Cold start on momentarily, back off. No smoke. On 20 seconds 30mv on the bias. No smoke.

ben62670

18,000 uf at 81.7 volts x 4. 84,000uf at 81.7 volts = grown man with tears in his eyes. Time for another power cycle.

ben62670

Mental note. Large metal output transistors contain some form of alternating current. Use caution when reaching for bias testing legs on output circuit.

unc2701

What's that noise? It's your brass balls knocking together.


Be careful there, dude.

ben62670

blue balls

heres what has been going on

http://www.diyaudio.com/forums/showthread.php?s=&threadid=92926&perpage=10&pagenumber=1

I was told to look for open 10ohm resistors, and I found all 4 were open!

Input ground was running through the preamp. No way to get proper bias ajustment, or DC offset

Systems

Nice,making fun of our attempts to help you (post#14at diyaudio):rolleyes:

doggie750

Hello Ben,
Just wanna say that you are in good hands, ANATECH from DIY helped me with my Carver once. He's a PRO. You are in my thoughts and prayers.....I've been in your shoes before so just have faith with the DIY gurus.....

Just a thought: You might wanna replace the coil/ power supply due to the overheating issue.

Merry Christmas and a Prosperous New Year:D

ben62670

GV#27 wrote:

Nice,making fun of our attempts to help you (post#14at diyaudio):rolleyes:

I should have been more specific. I was poking fun at me for playing with live electricity.

"Replaced the caps, and some of them exploded."

"I will hook it up to my SDA2's because they can handle the most power out of my speaker collection. I'm just kidding, and I only said that because I know you guys can't slap, and sterilize me so I don't reproduce via the INTERNET."

"Cold start on momentarily, back off. No smoke. On 20 seconds 30mv on the bias. No smoke."

"Mental note. Large metal output transistors contain some form of alternating current. Use caution when reaching for bias testing legs on output circuit."

I caught a little juice inspired me on that last quote :eek:

Actually if I were to give out a prize for best guess on what the problem was it would be a tie for leaking caps, and ground loop issue via the input boards, due to four 1/4 watt 10 input resistors.

Many thanks to all who posted. Without the posts here I would have never gotten as far as I have come, and I am still trucking along

heiney9

Glad we could get you pointed in the right direction and it sounds like things are working out for you so far. Anatech knows his stuff :cool: .

H9

Systems

ben62670 wrote:

I should have been more specific. I was poking fun at me for playing with live electricity.

OK I forgive you.:D

Its great you found someone(Anatech) that has expierience with that particular amp.

Be sure to practice safe electronics.

ben62670

Done and Done
Seems to work perfect!

Thanks for all your help!

Systems

Great:)