Another pair of GFA-565's go under the gun

ben62670

Well I am working on a pair of GFA-565's for a Polkie. This one is the worst case I have seen yet. The Caps are so bad that a couple of the legs have disintegrated. Well I have the input boards removed, and the gun hot. Time to get busy.
Ben

heiney9

ben62670 wrote: »

Well I am working on a pair of GFA-565's for a Polkie. This one is the worst case I have seen yet. The Caps are so bad that a couple of the legs have disintegrated. Well I have the input boards removed, and the gun hot. Time to get busy.
Ben

Dammit!!! We want pics.................we want pics.





















Hey Ben we need pics

george daniel

Those 565's have gotta belong to someone who lives west of Atlanta.

ben62670

OK, and yep yep yep.

ben62670

OK where you see bad cap that is where the cap was. Notice the stains. Where you see good cap someone had replaced them, and not the others Where you see Servo IC that is where the DC offset opamp is located. It is too close to the nasty cap so I just replace the unit anyways because they are cheap, and this is what regulates DC offset. Good caps will be replaced too, and I had also removed the bias trim pot for the ultra sonic cleaning process. They don't like to get wet;)

steveinaz

heiney9 wrote: »

Dammit!!! We want pics.................we want pics.
Hey Ben we need pics

That's right. No pics, then it didn't happen.

Oh...sorry man , you got pics. I guess it DID happen.

Systems

Are these the models that had the wrong voltage caps installed?
Since it uses a DC servo I guess they were able to eliminate an input coupling cap?

ben62670

GV#27 wrote: »

Are these the models that had the wrong voltage caps installed?
Since it uses a DC servo I guess they were able to eliminate an input coupling cap?

What happened with these amps is unfortunately Elna had a bad run on caps that failed over time and leaked all over the input boards. I think that you are correct that these are direct coupled amps;)

ben62670

Cleaned, and ready for re-population. The US cleaner, and simple green goes a long way;) Compare to earlier pic of board:eek:

ben62670

ReCapped, and trim pot reinstalled. I need the OpAmp though. I wish you could just run to the store for these.

danger boy

what would happen if you replaced the wires inside with silver wire?

Just curious...

ben62670

One mod some guys do is to replace the bars with wire. I have not tried it yet, but there is supposed to be a decent difference. Its kinda like doing away with the jumpers, and using wire on bi ampable speakers.
Ben

fbm211

Could you show us 565 owners where to solder on 12uF caps onto the main caps for that other mod you suggested.

RuSsMaN

Where do the tubes go?

ben62670

fbm211 wrote: »

Could you show us 565 owners where to solder on 12uF caps onto the main caps for that other mod you suggested.

Non polars right across the top of the main caps;)

ben62670

RuSsMaN wrote: »

Where do the tubes go?

In my pre:)

hoosier21

man I leave for vacation and my amps are ripped open, cleaned and repaired, good deal.

Ben, let me know what op amps to get and I will get them going.

Thanks for the work, looks great so far.

Russ

ben62670

I'll get that list to you soon.
Its looking pretty good. This was the bad one;)
Ben

ben62670

Well I finished the bad one. Took a little hunting. There was an open resistor on the board(r135 83r 1/4w fusible). It was only pushing, and not pulling. It was very distorted. Now it is beautiful, and DC offset is <10mv This is great news. These thing are a **** to fix!
Ben

ben62670

Here goes number two. I have it all apart. This one is a mess too. Looks like they let a kid do the soldering on this one. I can't believe they went through the trouble of replacing the caps, but did not clean it. This one is just under 1vdc DC offset. They stuck a big ugly 1/2 watt resistor in the signal path where a 1/4w resistor is supposed to go. Time for the board to take a bath in some simple green in the ultra sonic cleaner.
Ben

ben62670

Second one done. All new caps like the other. DC offset less than 4mv right out the bath:D I am very pleased. These things are at new specs, and good for a long time to come. I don't want to give these back. They run better than mine:mad:
HEY RUSS I'M DONE!

engtaz

Great job Ben.

engtaz

zingo

I too like your work Ben.

ben62670

Thanks Guys. I am very pleased with the outcome. I am going to have to do mine. I have one that isn't behaving very nicely. One gets a DC offset that swings up to 8vdc:eek: Not good for speakers at all:(
Ben

ben62670

Well I finally got tired of looking at my GFA-565's. It was their turn today:) Both are running to the same specs as Russ's:D I am very pleased:D:D. I can now run 4 565's, and a 585 on my big speakers. It'll be interesting:D:D:D
Ben

ben62670

Ya know what I like most about the amps I have repaired. Most of them you can tell someone else was in there trying to fix them. Even funnier is the repair shops that have put their name on the shoddy work they have performed:p