I have a Adcom 555 mk2 that I bought in 1990. It barely gets warm and runs flawlessly with tremendous bass extension and definition. Its sound staging and depth are also amazing. I am biamping with the Adcom on lower midrange and bass and a Conrad Johnson mv55 on upper midrange and treble. I alternate with a Hafler 120 during the spring and summer and the Connie-J. at fall and winter. The Adcom is indestructible and the only maintenance I perform is checking all connections and dusting out the interior every 18 months. Its going on 34 years and I'm confident it will reach 40!! My Hafler dh120 is 37 and both have seen different speakers over the years, Sansuis, H.H.Scotts, Ohm Walsh 3's, Vandersteen 2ci's, Energy veritas, and the Maggie 1.6's along with the Vandersteen 2w's which are a end game for me!

What a great way to start your channel. I have three of these and love them, and your video is most appreciated.

That amp is likely good to go for another 35 years. Well done sir.

You have great knowledge and skill. Explanation was on point. Great job!

I have this exact same amp!!! it's a dream 200 watts at 8 ohms. i use it too power my front left and right channels i use a outlaw mono block for the center! works so well as the front stage! best part only paid $200.00 for it !!

Enjoyed your presentation, thanks!

Excellent video! I don't have this amp or need to repair it, but I came across the video while looking at Adcom's newer amp which shares the same chassis, design and base model name. As a former electronics engineering student, this is an excellent breakdown of troubleshooting. I enjoyed!

awesome video and sweet setup

Excellent video! I worked on one a couple of years ago that had a failed power supply and a bad zener diode.

Glad I found your channel. Nice video and thanks for sharing, Steve

Good video, I love the Adcom 555

Gawd! I love Adcom. What day and age is it that such a boss audio company goes kaput?! See a lot of the pre amps around on the used market, not so much the amps. Thanks for the vid.

Thank You for this Cool Insight on these Very Powerful and under appreciated Adcom amps. I am now subscribed to your channel. I have 3 of these Bad Boys, 2 of them have been fully restored and matched to each other all of them Driving Reconed Cerwin-Vega 12s and 15s from one common/daisy chained preamp (Yamaha RX797) output. Front Row Concert Sound in my Basement. -When My wife is not home lol.

Creative video, thanks :)

I have a GFA555 that one channel stopped working. The rail fuses are all testing good. I am a weekend electronics hobbyist from 30 years ago and not sure the high-end audio world passed me by while I raised my family and am now empty nest and looking to a) repair/refurb my GFA - or - b) replace it (with what that would sound as good as the GFA without spending $4,000). I built several Dynaco kits back in the day and even a 100W/channel into 8 ohms RCA (schematic) power amp from scratch built into an old AM carrier current gutted chassis that had some minor hum because I didn't do a good job of grounding - but that amp still sits on a shelf somewhere in my basement and likely still works albeit, it's just there to make me feel accomplished as I am a self-taught electronics hobbyist and really only have a VOM on my bench and nothing else to work with other than the minor knowledge I have to do what I've done - and the desire to want to see my GFA555 working again. Do I rebuild and if so, where do I get the parts? Or do I replace and, if so, with what and at what silly stupid expensive price? I LOVE my GFA555 and my ears tell me nothing on today's market will sound any better...............so why replace if I can repair/refurb it? PLEASE - any help, guidance/direction you can give me Erik, would be greatly appreciated! As well, I don't know how to reach you (email?) so I have to post here to ask. A musician, high-end hi-fi enthusiast, and weekend auto and electronics hobbyist who has enough skills to be dangerous - and capable! Thank you in advance for whatever you can do to help me with my GFA555 dilemma. Mitch

Beautiful condition subbed,I like your channel

Up here in Canada I had an Adcom. I really found the sound cold and uninteresting. Well built. Perhaps even very well built. Just I look at sound from being expressive and yet delicate. I mean I could push the amp to it's max and it had no distortion. One other amplifier circuit was not as simple but was effectively more robust while able to produce very high quality sound. Rebuilding a damaged amplifier takes knowledge of more than reading a schematic diagram. Understanding

Very very detailed, and helpful. Appreciated !

Thanks for this video. I've had an Adcom 555 Mk11 in my shop for months while I get my nerve to tackle it. (Dead on one channel).

Cheers.

Great Video! @EriksElectronicsWorkbench, do you have a service center? I have a GFA-585, and 2 DBX-BX1's Id love do send in for maintenance. Maybe you are are in the LA area, so I dont have to ship those beasts?

What is the disconnected blue wire pair with white JST connector on it on top of the transformer?

Hi Eric my GFA 555 II hadn't been in use for a while and recently when I turned it on I noticed the right channel heat sinks ran too hot and the channel tended to shut down. I can't remember which one but I did notice some fluid leakage on one of the boards. I gave it to a local shop for service and they claim it isn't troubling anymore. Although I noticed the right heat sinks running hotter. I have no knowledge of electronics but don't want to harm the amp by being ignorant. Specifically could you advise what to check and what to replace as a way to.ensuring the amp doesn't have the over heating problem. Thanks.

I have two modified Adcom GFA-545 mk II amplifiers, and a GFA-535 mk II amplifier. I must have a later revision board of the 545 amplifiers. There are extra components that are not in the schematic. Is there information on board variations somewhere?

I am having hum from my 555 II that might be ground loop hum, maybe not. To make the grounds common, I plugged in the amp and the surround sound processor into the same wall outlet. (Both have polarized, two-prong plugs.) No other devices were powered on. Still humming. But there's no hum when inputs to the amp are taken out. The amp by itself is quiet. Then I plugged in my old Dynaco PAS 3X preamp to the amp and hum is there again, so I guess the problem is not in my surround sound processor. And the hum increased by the volume control. Is there anything internally in the amp that could cause this. Do you have any other thoughts? By the way, in normal operation, none of the other surround amps hum, only the Adcom. Thanks, Carl

Do you want to freshen up a Nakamichi Receiver 1? Can't find anyone local.

Hello Erik great video! I have an old GFA 555 AMP that needs repair. I think it is maybe 40 years old. Can it be repaired? good idea? thank you!!!

I’m getting some static in my right channel that almost sounds like it’s getting a radio signal from a router or phone. Curious if this is an issue with my amp? Also where are you located if I can have you look at my amp?

Hi, I’m a subscriber. My class A amp, (adcom gfa5802) just recently developed a slight buzzing hum on the left channel. Do you think the filter capacitors for the left channel are bad? I checked the DC voltage at the speaker terminals and they’re at 0.025V, so I think the coupling capacitors are fine. Or do you think it’s something else? Thanks in advance.

Erik - could you point me toward the speaker protection relay and monitor circuit for each speaker output? You said that "these are commercially available and could be installed inside the amplifier," but I need help finding the items. Thanks, Carl Espy

I just purchased an adcom 7607 which is a 7 channel amplifier. I purchased it as parts or repair. It won't power on. I thought I could find someone familiar with these but having zero luck. Without taking up a bunch of your time, would you have any idea what I may be able to check quickly to possibly resolve without having to ship the amp cross country for 3 months?

I have had this amp for 30 years and I have been trying to get it going and it is having the exact problem as this one, same right side too. How much would it cost me to have you fix it?

I heard these amps do no have speaker protection. What is the best way to protect the speakers, playing them at low volume?

Did you test the main power supply 15k uf capacitors in circuit? I don't have the Peak meter you have, but my Fluke meter shows each one (in circuit) is very close to 15k. Couldn't measure ESR, though.

Hi l do have 555 ii amp works good, how can I have it check out.

Hi Erik: I have the exact same amplifier purchased new sometime in the 1990s. The amp has been used very little in the last 20 years. Once a channel went out way back when and I had someone look at it. It was so long ago I don't remember. I sometimes power up the amp and about three years ago a fuse was blown. I replaced the fuse and it has worked OK. However, I only power this amp up once every three months or so. Now I want to use the amp again on a regular basis , however I am told if it fails it can destroy the speakers. I have B&W 802 speakers. Should I go ahead and use the amp or should I have it check? I am using the B&W 802s on my home theater, but the AVR amp is probably not as nice as the Adcom.

I’m shocked that this amp doesn’t have output protection circuitry to prevent that kind of offset to get to the speakers! 🤯 I have the Adcom 545 and check it every so often. But it can always fail when in use. 😱

Can you please list the capacitor values you have changed ? thanks

Not sure if the 555ii simply had more units sold than the Adcom 5500. I do see way more vids and repair vids on the 555.

Where are you located? Are you a business? Thanks.

nice amp. bat erik, i had a problem whit mi amp.. i dont no how match bias volt i need. the amp is a realisitc 32-9003. from the 80ste. ant i ripaer it, bat dont now the volt of it. can you help mi ( pls ) it runs now good, so now the setting bias. schematic is on internet.. if i send you te link??? is it possible ant look for a minit ? gr huug sorry for mi shitty englis 😐😐