Replacement circuit boards for Adcom GFA-565's with leaky caps
Hey DIY'ers. Just wanted to share with you, an elegant solution to the leaking capacitors in GFA-565's.
https://hoppesbrain.com/2016/05/09/how-to-fix-leaking-capacitors-in-adcom-gfa-565-for-good/
A lot of people struggle with fixing these amps—it's really hard to get it all cleaned off—and personally I don't want to deal with that
electrolyte ever again!
Hey DIY'ers. Just wanted to share with you, an elegant solution to the leaking capacitors in GFA-565's.
https://hoppesbrain.com/2016/05/09/how-to-fix-leaking-capacitors-in-adcom-gfa-565-for-good/
A lot of people struggle with fixing these amps—it's really hard to get it all cleaned off—and personally I don't want to deal with that
electrolyte ever again!
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Yep, it's the input board.
The idea wasn't to clone the GFA-565—I just want to make it easier to repair the capacitor issue, without complications from sneaky, leaky electrolyte.
But I suppose you could use the board to clone a 565. You'd still need to build an output section, but it's a simple circuit and if you don't want to make boards for that, it could be done the old-fashioned way with TO-3 sockets and point-to-point wiring.
But it's probably easier to just buy a broken GFA-565 and install the board.
The idea wasn't to clone the GFA-565—I just want to make it easier to repair the capacitor issue, without complications from sneaky, leaky electrolyte.
But I suppose you could use the board to clone a 565. You'd still need to build an output section, but it's a simple circuit and if you don't want to make boards for that, it could be done the old-fashioned way with TO-3 sockets and point-to-point wiring.
But it's probably easier to just buy a broken GFA-565 and install the board.
Revision 2.0 boards arrived today! Even better. Plated through-holes, and all minor errors have been corrected. (Hole sizes, spacing, silkscreen legibility, etc)
https://hoppesbrain.com/2016/07/19/adcom-gfa-565-replacement-boards-revision-2/
https://hoppesbrain.com/2016/07/19/adcom-gfa-565-replacement-boards-revision-2/
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personally i havent officially seen any, but in recent threads i have read people saying the 555ii's have the leaky cap issues too as well as cheap "glorified cardboard" boards. just curious if this was a needed part for the 555ii.
the boards you had made look great! im sure that was a lot of work.
the boards you had made look great! im sure that was a lot of work.
Actually, I've researched this some more, and I'm pretty sure of these equivalents...
1ss82 = BAV21
1ss178 = 1N4148TR Vishay
The one's I can't find replacements for are the KB262 and KB362 "Varactor diodes". I can't even find a decent data sheet for them, just a few specs in tables. What I gather is that these are diodes that vary their forward voltage drop with current. All diodes do this of course, but I think these are designed for this effect, with a steeper curve.
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Huh, I haven't heard of that. The 555 II boards seem pretty decent to me. Just your standard FR4's. It's true that these are nicer though! I'm really impressed with the quality from Seeed Studio's Fusion PCB service.
i will try to search for the links to the threads. some are saying the 555ii boards are very crappy & absorb the leaked electrolyte like a sponge causing shorts & problems & then need to be ultra sonic cleaned multiple times (a dozen) to get it all out...
i agree with your comment, when i look at the boards in my 555ii's they look pretty decent, made from a hard plastic material, not cheap fibre or cardboard like some are saying. maybe they are confusing the 565 & 585 boards & caps with the 555ii's??
also have read &/or been told that ALL the caps in the 555ii's were either complete crap quality &/or defective/leaky & they ALL need to be replaced. yet another reputable member here says they are top notch quality caps & only a small batch were defective mainly in the 565 & 585 amps. forums are great for info & help with things, but the opinions, myths & heresay can be hard to sift through for accurate reliable info.
luckily i dont have a 565 or 585 but im sure many owners of these amps will be happy theres now an option for the bad boards.
http://audiokarma.org/forums/index.php?threads/adcom-gfa555-overheating-issue.723967/page-2
http://audiokarma.org/forums/index....55-ii-amplifier-with-insurance-policy.712851/
i agree with your comment, when i look at the boards in my 555ii's they look pretty decent, made from a hard plastic material, not cheap fibre or cardboard like some are saying. maybe they are confusing the 565 & 585 boards & caps with the 555ii's??
also have read &/or been told that ALL the caps in the 555ii's were either complete crap quality &/or defective/leaky & they ALL need to be replaced. yet another reputable member here says they are top notch quality caps & only a small batch were defective mainly in the 565 & 585 amps. forums are great for info & help with things, but the opinions, myths & heresay can be hard to sift through for accurate reliable info.
luckily i dont have a 565 or 585 but im sure many owners of these amps will be happy theres now an option for the bad boards.
http://audiokarma.org/forums/index.php?threads/adcom-gfa555-overheating-issue.723967/page-2
http://audiokarma.org/forums/index....55-ii-amplifier-with-insurance-policy.712851/
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No idea where this paper circuit board thing is coming from. (Phenolic?) Every Adcom I've ever seen has been basic fiberglass. But there are people on this forum with more experience than I, so who knows?
I have only seen a couple 555's with electrolyte leakage, but it was just a tiny, tiny amount. Nothing like the 565 and 585's Elna caps that blow up all over the place!
The electrolytic caps in the Adcoms are just so-so quality, and more than 20 years old now. They should all be replaced.
My 565 boards don't work in the 585. The circuit is the same, but the board is physically different.
I have only seen a couple 555's with electrolyte leakage, but it was just a tiny, tiny amount. Nothing like the 565 and 585's Elna caps that blow up all over the place!
The electrolytic caps in the Adcoms are just so-so quality, and more than 20 years old now. They should all be replaced.
My 565 boards don't work in the 585. The circuit is the same, but the board is physically different.
yep same here, every 555, 555ii & 545/535 i have owned have all had the hard plastic/fiberglass boards. just going by what ive read recently... who knows.
i do agree that aged caps should be replaced, in electronic gear as well as speaker x-overs. i plan to replace the caps on the input board of my 555ii's very soon as well as the bigger ones on the output boards. the big power caps look to be fine & most have said they are high quality & rarely go bad in the 555's.
thanks for the info.
i do agree that aged caps should be replaced, in electronic gear as well as speaker x-overs. i plan to replace the caps on the input board of my 555ii's very soon as well as the bigger ones on the output boards. the big power caps look to be fine & most have said they are high quality & rarely go bad in the 555's.
thanks for the info.
Yes, the filter caps are very rarely bad. But if you want to get another 30 years out of it, I recommend replacing.
You can also judge the approximate power-on time of the amp, and thus the capacitors, by looking at how much the circuit board is browned around the driver transistors, and on the little boards on top of the caps, above the drain resistors. Of course, it's bad for the caps if the amp sat idle for a long period. But if you see a lot of browning, then you know the caps have a lot of time on them.
Some of the early, rack-mount models of GFA-555 have 80V filter caps instead of 100V, and I see these go bad more often. The supply voltage is 80V!
I use Panasonic EEU-ED2E470 (47uF 250V) on the output boards. Sometimes these are only 100V caps, and they do explode from time to time.
You can also judge the approximate power-on time of the amp, and thus the capacitors, by looking at how much the circuit board is browned around the driver transistors, and on the little boards on top of the caps, above the drain resistors. Of course, it's bad for the caps if the amp sat idle for a long period. But if you see a lot of browning, then you know the caps have a lot of time on them.
Some of the early, rack-mount models of GFA-555 have 80V filter caps instead of 100V, and I see these go bad more often. The supply voltage is 80V!
I use Panasonic EEU-ED2E470 (47uF 250V) on the output boards. Sometimes these are only 100V caps, and they do explode from time to time.
Yep, Nichicon LNR2A153MSE
Unfortunately, they don't fit into the old brackets due to their smaller size, and you'll need to drill new holes. However, this is a good opportunity to clean up the layout a bit. I put the caps side-by side and put the bridges down on the chassis for better heatsinking.
Unfortunately, they don't fit into the old brackets due to their smaller size, and you'll need to drill new holes. However, this is a good opportunity to clean up the layout a bit. I put the caps side-by side and put the bridges down on the chassis for better heatsinking.
is that # for the 555ii? the ones in my 555ii amps are 47uf 160v but will get replaced & im sure a higher volt rating is a good thing for those.
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