The amp works and has near zero voltage at the speaker terminals when nothing is connected. I am told this is a very good sign.
I was told if the amp is faulty it can fry speakers. I still have the 802 B&W speakers that came with the amp back in the early 1990s.
Is it safe to use the amp? It works fine with the current PA speakers attached to the amp. At most I have used the amp every three or four months during the last 20 years. It blew a fuse once and I was able to replace the fuse and it continued to work OK.
Should I service the amp even if it is in good working condition?
I was told if the amp is faulty it can fry speakers. I still have the 802 B&W speakers that came with the amp back in the early 1990s.
Is it safe to use the amp? It works fine with the current PA speakers attached to the amp. At most I have used the amp every three or four months during the last 20 years. It blew a fuse once and I was able to replace the fuse and it continued to work OK.
Should I service the amp even if it is in good working condition?
A faulty amp can fry speakers, that is true.
Your description shows no sign of a problem and as you say yourself it works fine with some PA speakers. If the amp has no history of suddenly zapping speakers or doing anything it shouldn't then it will be fine.
So the answer is yes based on what you have told us, it is fine to use with whatever speakers you wish.
Not necessarily, we see so many cases of recaps and such like that end in tears. It all depends on your skill level and competency.
Your description shows no sign of a problem and as you say yourself it works fine with some PA speakers. If the amp has no history of suddenly zapping speakers or doing anything it shouldn't then it will be fine.
So the answer is yes based on what you have told us, it is fine to use with whatever speakers you wish.
Not necessarily, we see so many cases of recaps and such like that end in tears. It all depends on your skill level and competency.
A second vote to leave well enough alone. Occasional use over 20 years is actually
the best case scenario for the amp being in good condition.
If you are still too worried about it, use some 2A speaker fuses until you are more confident.
Or just leave them permanently in line.
the best case scenario for the amp being in good condition.
If you are still too worried about it, use some 2A speaker fuses until you are more confident.
Or just leave them permanently in line.
I mostly used the amp in the 1990s. Then I moved and did not have a room to listen to music anymore. I set up an AVR theater for the family in the TV room and the Adcom amp went down to the basement where it was used very rarely to power PA speakers. The idea was to play live music, but it never happened. So the amp has been mostly turned off for years.
I would not recap the amp myself since I am a klutz and do not have good eyes anymore. I am not sure there are amp techs where I live in Maryland. I may simply open up the amp and inspect the caps to see if there is any chance they leaked. I saw a video where leaky caps caused short circuit on the boards.
In any event I am just looking for reassurance before I hook up the amp again to my B&W 802s. I am using the latter in my home theater, but they are likely underpowered by the AVR.
Thanks so much for your words!
Years ago when he was first starting out, this gentleman would supply updates to Adcom products. He is still in business and offers some prebuilt modules to update old amps. I have used him in the past. Solid.
https://hoppesbrain.com/
https://hoppesbrain.com/
Chris (hoppesbrain) is a member here and will probably chime in. I have rebuilt several of my Adcom amps with his parts, excellent products!
In the mean time, go over to his website, as listed in the above post, and dig through the FAQ section.
Dan
In the mean time, go over to his website, as listed in the above post, and dig through the FAQ section.
Dan
Let the caps reform, use the amp on spare speakers, after a week of daily use, switch to the expensive speakers if there are no issues.
And do check for bulged or leaky caps.
Spray the selector switches with something like 2-26, it forms a protective film on the contacts, to prevent corrosion related issues.
I have used it on pots as well.
I use software control for volume, so less wear on the pots.
No ties to sellers, here we have several sellers selling 2-26.....
And do check for bulged or leaky caps.
Spray the selector switches with something like 2-26, it forms a protective film on the contacts, to prevent corrosion related issues.
I have used it on pots as well.
I use software control for volume, so less wear on the pots.
No ties to sellers, here we have several sellers selling 2-26.....
I saw his website; impressive! I do not think I can work on the amp. The only time I have done any work like that is wiring an electric guitar. I will open the amp and if the caps are not expanded and leaking I may not do anything. My only concern is that caps have a half life whether the amp is used or not. But, then again I hear anecdotal evidence of people that have no issues with stock old amps. In my experience guitar amps hum when the caps are bad.
Thanks so much!
Hey Julian, +1 on what others have said. The fact that it's been powered on occasionally over those 20 years means a lot. I'd be worried if it just sat and sat and sat, just because of the capacitor oxide formation issue. They do need to be powered on occasionally to maintain that insulating layer in the caps.
Anyways, bad caps are rare in GFA-555 II's. (It's the GFA-565 that had the bad batch of caps) There's only four electrolytic caps on the input board, which are under little stress and rarely if ever fail, there's four electrolytic bypass caps on the output modules. These sometimes go bad with heavy usage. And finally there's the main filter caps, and those are 99% probably fine. In any case, none of these caps should cause speaker blow-outs if they go bad.
The main cause of 555 II's blowing up is user error, shorting it out, overdriving it, or letting it get overheated because of poor ventilation. Otherwise they're super reliable. I mean, not 100%, but there's risks in every hobby.
Anyways, bad caps are rare in GFA-555 II's. (It's the GFA-565 that had the bad batch of caps) There's only four electrolytic caps on the input board, which are under little stress and rarely if ever fail, there's four electrolytic bypass caps on the output modules. These sometimes go bad with heavy usage. And finally there's the main filter caps, and those are 99% probably fine. In any case, none of these caps should cause speaker blow-outs if they go bad.
The main cause of 555 II's blowing up is user error, shorting it out, overdriving it, or letting it get overheated because of poor ventilation. Otherwise they're super reliable. I mean, not 100%, but there's risks in every hobby.
The other thing is check for PCB scorching around the TO-126 transistors. If the board is badly scorched, then the amp might have been run with poor ventilation and gotten hot a lot. If so, re-flow these solder joints, they sometimes get cracked from heat cycling.
The Adcom's that landed on my bench - they all got added heatsinks for the driver transistors, and a cooling fan as additional insurance.
Wow, another highly reassuring post. Thanks so much!
I ordered a switch box to use the Adcom GFA 555ii amp for music and to then use the AVR when watching TV. I will drive the speakers with alternating amps depending on whether I am watching TV or listening to music. I have listened to my B&W 802s with the Denon AVR for a long time and forgot what they sound like with the Adcom.
It's been noted online all over the internet that those "A/V" receivers are lousy for any critical music listening.
Most people don't care, not aware, or are just accustomed to mediocre sound quality, not knowing the delicate "purity" of sound that can be had from a dedicated 2-channel amplifier/receiver designed strictly for music.
I will set it up this weekend. It has been a long time since I had the 802s on that amp. I had forgotten my passion for audio and it is coming back now that I am retiring. I may even put acoustic panels on the walls.