Repair Advice

[heiney9]

I have a small problem with this Adcom GCA-510. It's a high gain "integrated" amp that uses a completely passive pre amplifier section. Actually there is no typical pre-amplifer stage. They refer to it as "line stage"

It has playback and recording switching, bal. control and vol. control. It seems the Right channel has an intermittent cut out and can get very slightly fuzzy at times. It's completely random independent of volume level or run time. Comes in and out or sometimes not at all.

Any ideas where to look for cold solder joints. I used Caig on all the controls as it acts like a dirty/dusty potentiometer. That didn't help at all. I'm thinking of pulling the rail fuses and cleaning those as well as the fuse holders. Except as you can see in the picture the fuses are in a very, very tight area. I can't get my fingers in there to pull them. Any ideas????

Also if I wanted to inspect the bottom of the main board how would I do that without de-soldering all the trannies? I suppose I could remove the entire assembly cooling fins and all. I'm thinking more along the lines of bad solder joint vs bad components.

Here's a long distance (borrowed) picture of the innards.

Ben would you work on this? Not much hope of getting the service manual as this was a fairly rare, limited run piece mostly sold in Canada and overseas.

[heiney9]

TTP.......Somebody has to have some advice or discussion.:)

[BigMac]

Hi. I have no repair experience at all but here is a schematic of the insides of your unit. I could not find a repair manual but if I do I will post it. Hope this makes sense to you or someone else. It is Greek to me,lol. Hope this helps you out some.

Link: http://www.sendspace.com/file/ye28sr

[engtaz]

Cold solder joints are usually hair line crack in the solder. usually where compenent lead is soldered to the board. You should be able to lift the whole assemmbly out tranformer and all.

engtaz

[engtaz]

Great job BigMac

[heiney9]

Hi. I have no repair experience at all but here is a schematic of the insides of your unit. I could not find a repair manual but if I do I will post it. Hope this makes sense to you or someone else. It is Greek to me,lol. Hope this helps you out some.

Link: http://www.sendspace.com/file/ye28sr

Thanks a lot for the link!!!! Where did you find that? DIY Audio?

Cold solder joints are usually hair line crack in the solder. usually where compenent lead is soldered to the board. You should be able to lift the whole assemmbly out tranformer and all.

engtaz

It's been a while since I did any trouble shooting............any tips on what to look for visually or where in the circuit to start?

H9

[billbillw]

Heiney, when you say you used Caig, do you mean the 5% Deoxit flushing spray? That is what you should be using for cleaning pots/switches.

If so, did you use it on those input slider switches too? (I am assuming that is what I see towards the bottom/front of the gut shot)

Those are notorious for causing cutouts.

As far as finding cold solder joints, you usually need to see the bottom of the circuit board. Get a magnifying glass and start by looking for joints that are dull or otherwise look different that all the others. Examine those more closely to see if there are any visible cracks. Sometimes you need to put some pressure on the leads to see the crack. I usually re-flow any leads that are suspect to be sure.

Good luck.

[BigMac]

Thanks a lot for the link!!!! Where did you find that? DIY Audio?


I called Adcom and asked them to send me a schematic so they emailed me one. Then I just uploaded the .pdf to a server you could get it from. They did not have a repair manual but I think I may have found one that someone put together. Just waiting for a response back from them. I hope to get a response but ya' never know.

No DIY audio but I did read that particular thread you are referring to with yourself and Ben. Was looking all over the place to try and find out something to help you. All I located was the manual doing the normal search on Google and a few other search engines and that would have been no help for your issue.

[engtaz]

I will try to look at the schematic when I get off work.

engtaz

[ben62670]

It doesn't look too complicated compared to a 585:) I am guessing like others have suggested a solder joint gone bad, or a DC blocking cap. You could trace the input wires from the selector switch and bypass them so a single source would go straight to the volume pot. Also you could try flexing the boards a bit. I can't read the diagram well enough to see values.

[heiney9]

I called Adcom and asked them to send me a schematic so they emailed me one. Then I just uploaded the .pdf to a server you could get it from. They did not have a repair manual but I think I may have found one that someone put together. Just waiting for a response back from them. I hope to get a response but ya' never know.

No DIY audio but I did read that particular thread you are referring to with yourself and Ben. Was looking all over the place to try and find out something to help you. All I located was the manual doing the normal search on Google and a few other search engines and that would have been no help for your issue.

Thanks again for your help............didn't cross my mind to call Adcom. I keep forgetting they are still a viable company and have really good support.

It doesn't look too complicated compared to a 585:) I am guessing like others have suggested a solder joint gone bad, or a DC blocking cap. You could trace the input wires from the selector switch and bypass them so a single source would go straight to the volume pot. Also you could try flexing the boards a bit. I can't read the diagram well enough to see values.

Not sure there are DC blocking caps. This is a very simple design, I'm guessing production was around 1997-1998.

I'll give a bit more background. The thread I started on DIY awhile ago was for a different GCA510, it was my brothers. I was going to buy it from him but is basically had the same issue I'm now having with a different GCA510. Before he sold his unit on ebay he ttok it to the only local repair shop in town and they gave it a clean bill of health. He never heard anything from the buyer after he sold it.............but it never worked right I thought.

It seems now I'm having the same issue only on a more intermittent level. I've tried using different cables both I/C's and speaker cables. Different sources, etc. to isolate the issue to the unit.

As far as Caig, I used Dexoit and I did get into the switching, bal and vol controls as good as I could.

Keep the ideas coming. It will be awhile before I tear into it to try and find a cold solder joint. I suspect that's what it is.

[sucks2beme]

I second the visual check of the board for solder breaks.
Get yourself a good lighted magnifier and go nuts. I found a
solder pad crack on one of the inputs for my Parasound pre.
The problem was driving me crazy.

[TNRabbit]

I second the visual check of the board for solder breaks.
Get yourself a good lighted magnifier and go nuts. I found a
solder pad crack on one of the inputs for my Parasound pre.
The problem was driving me crazy.

Wow; it must have sucked to b u...


:D

[heiney9]

EDIT:

Actually the unit was probably manufactured around 1993-1994 not 97-98. I'll go to the "old" peoples store and get a lighted magnifyer........that's a good idea!