Fixing an Adcom GFA 555

[pablo_rodz]

Hi all,

I just got a used Adcom GFA 555, it looks different to all the 555's I've seen, so I think it's kind of old.

The amp was cheap because the right channel RCA Jack is broken. I thought it was going to be an easy and cheap fix, but the two (2) RCA inputs are in one plastic unit. I need help finding a new RCA jack "thingy". At least the amp powers up and seems to work.

Below are pictures of the amp opened up and the RCA jack plastic unit/thingy :confused:

It looks clean, the caps are not swollen or leaking everything looks great.

http://i48.photobucket.com/albums/f228/pablo_rodz/VW%20R32/CIMG2901.jpg

http://i48.photobucket.com/albums/f228/pablo_rodz/VW%20R32/CIMG2902.jpg

The broken Right Channel RCA Jack
http://i48.photobucket.com/albums/f228/pablo_rodz/VW%20R32/CIMG2908.jpg

The back of the RCA jacks
http://i48.photobucket.com/albums/f228/pablo_rodz/VW%20R32/CIMG2909.jpg

The plastic RCA jack unit
http://i48.photobucket.com/albums/f228/pablo_rodz/VW%20R32/CIMG2912.jpg

This is where the RCA's are soldered to the board
http://i48.photobucket.com/albums/f228/pablo_rodz/VW%20R32/CIMG2913.jpg

http://i48.photobucket.com/albums/f228/pablo_rodz/VW%20R32/CIMG2905.jpg

http://i48.photobucket.com/albums/f228/pablo_rodz/VW%20R32/CIMG2903.jpg

[AudioGenics]

check out

http://www.parts-express.com/home.cfm

[cnh]

Don't most older GFA-555s just have TWO large Blue 30kmfs CAPS not four? So are those new mods to that unit?

cnh

[pablo_rodz]

check out

http://www.parts-express.com/home.cfm

I did check PE, but the RCA jacks they have are for chassis mount, I need the plastic RCA pad (L+R in one). If I cannot find it I'll have to rig-up something:confused:

[pablo_rodz]

Don't most older GFA-555s just have TWO large Blue 30kmfs CAPS not four? So are those new mods to that unit?

cnh

I have no Idea, the guy that sold it to me had no info. on it, he even asked what I wanted it for :eek:, that he had no idea why will some one need one...:rolleyes:

[cnh]

I may have been wrong about those caps....perhaps it is 4 X 15K. And 16 small caps.

See this link for a photo to compare with yours.

http://www.polkaudio.com/forums/attachment.php?attachmentid=16755&d=1148038682

cnh

[pablo_rodz]

I may have been wrong about those caps....perhaps it is 4 X 15K. And 16 small caps.

See this link for a photo to compare with yours.

http://www.polkaudio.com/forums/attachment.php?attachmentid=16755&d=1148038682

cnh


that is correct it has (Capacitor Technologies) 4 x 15000 MFD 80 WVDC
and 16 Toshiba small caps.

Does someone knows what does this mean on the Toroidal Transformer:confused: 01124 708 VA 11 85 ???

[pablo_rodz]

Anyone??
Does anyone know where I can find a dual RCA jack?

[Bigbang]

you might try and contact this guy...

http://www.alibaba.com/product-gs/50034743/RCA_Jack.html

or better yet save up some cash and send it to these guys...

http://www.musicaldesign.com/adcom.htm

or at least call them and see if you can source that part somewhere...

David

[RandyWilliamson]

Pedro....try:

www.jameco.com

they're very likely to have it...u may have to do extensive searching or call them tho.

Good luck....at worst you can rig one im sure.

[pablo_rodz]

you might try and contact this guy...

http://www.alibaba.com/product-gs/50034743/RCA_Jack.html

or better yet save up some cash and send it to these guys...

http://www.musicaldesign.com/adcom.htm

or at least call them and see if you can source that part somewhere...

David

Yikes that would be quite a bit of cash:(

I wonder If I could do some of that myself:eek:

[Lasareath]

Yikes that would be quite a bit of cash:(

I wonder If I could do some of that myself:eek:


I'm sure ben could do it

maybe you should PM him

[obieone]

+1. I'm sure Dr. Polkenstein can hook you up.

[pablo_rodz]

So Ben or Dr. Polkestein are the guys to find??

But I would like to learn how to do it....

[pablo_rodz]

Hi all!

I just ordered a pair of gold plated RCA Jacks to fix the amp. I couldn't hold my self and decided to hook-up my new Atrium 45 to the amp to see if it works....

Well the right channel works, music plays fine, but the left channel has a Humm/ buzzing sound. The humm is even present when I remove the Interconnect (cable).

Does anyone have an idea of what could be causing it?

[pablo_rodz]

+1. I'm sure Dr. Polkenstein can hook you up.

I tried searching by his name but I got no results...:confused:

[GV#27]

Does someone knows what does this mean on the Toroidal Transformer:confused: 01124 708 VA 11 85 ???Probably part#,VA rating (708)and date code.

[GV#27]

Does anyone have an idea of what could be causing it?Possibly a bad filter cap.Also did you make sure to isolate the body of the new RCA connectors from the chassis.

[CoolJazz]

Coupling capacitor maybe or you still have a open signal or cracked ground on that jack? Since you have obvious external damage, I'd focus on that first.

Coupling caps COULD be something like those round yellow caps that I think I see four of in one of those pictures. Somebody with experience on that amp might be able to send you right to the correct parts in there. Just know what your doing before you poke around in there...those big caps mean business and may hold a charge long after it's off!!

CoolJazz

[polrbehr]

I'm sure this is who Lasareath is referring to...

http://www.polkaudio.com/forums/member.php?u=76154

Ben knows about Adcoms, in fact he's who I bought mine from (GFA555).

He's also a pretty good guy, but that's just IMHO ;)

[cnh]

Ben is great at exactly this kind of thing among a whole host of others. And offers to help anyone out there who needs it. He knows his stuff.

When I first got my Adcom, he told me to drop it by and he'd take a look at my caps, etc, if I were down his way. I have a friend in Atlanta and occasionally get down there. I will certainly lug the Adcom down on my next trip.

Drop Ben a line and get an estimate...and check out your shipping options.

cnh

[dudeinaroom]

I don't believe those had coupling caps

[pablo_rodz]

I PM'd Ben....

Thanks...

Also, I haven't replaced the RCA jacks, I just ordered them today. How do I discharge the caps, before shocking myself???

Thanks again!

[GV#27]

I don't believe those had coupling capsI believe the original version did but the MK11 version omitted them in favour of a servo.

How do I discharge the caps, before shocking myself???

Thanks again!
With a >50 ohm 2watt resistor.

[RandyWilliamson]

where did u find the part btw?? should this ever so sucky situation arrive....I'd want to know.......

[pablo_rodz]

where did u find the part btw?? should this ever so sucky situation arrive....I'd want to know.......

I havent found the part, I'm going to try to "rig-it up".

[pablo_rodz]

Well I got the RCA Jacks, and solder iron today.... Can't wait for the weekend to "fix" the amp.

[pablo_rodz]

Can't wait for the weekend to "fix" the amp.

Well that didn't work! :(

The HUMM is still present, and louder.:confused:

I tried PMing Ben, but his PM's are maxed out!

[fbm211]

Not to jack this thread,, but WHERE IS BEN???...Anyone Know?Im a little worried as I havent seen any posts lately and thats not like him.

[hearingimpared]

Not to jack this thread,, but WHERE IS BEN???...Anyone Know?Im a little worried as I havent seen any posts lately and thats not like him.

Ben is in Conneticut visiting his mom.

[ben62670]

That amp has been modded quite a bit. You are going to need new jacks. I would just use some nice after market types.

[obieone]

Welcome back.

[pablo_rodz]

That amp has been modded quite a bit. You are going to need new jacks. I would just use some nice after market types.

Hi Ben, welcome back to the forum. Needless to say, you were missed!

Modded huh? I wouldn't have guessed that.

From the pics what would you say has been modded?

Also I replaced the RCA's with chassis mount gold plated jacks. I still have a fairly loud hum.

Thanks for your help