I am new to this trade so bare with me if I ask dum questions.
I have a AUDIO RESEARCH D-76A power amp that I been using for few months now. as you probably know this amp has the most tubes than any other tube amp that I can remember. the middle of the amp are four 12AX7. I notice that one of the 12AX7 [middle top] are not lighting up nor hot. so I had all the sockets replace but still no light nor hot. I was told that its normal. how could it be? will this de-grade my sound? please enlighten me. I will appreciate any advice. thanks
This is a job foooooor -- Hifigeek!! Or, you can call ARC and ask for Calvin. He's a great guy and I always found him extremely helpful.

Good luck.
What is the V number of that 12AX7 tube and I will investigate it for you.
I believe this are the original RCA tubes unfortunately most of the white numbers or letters are erased. all I can find are the red letters/numbers that says RCA afc 12ax7/ecc83. how ever I tried other four tungsol 12ax7 with no improvement. I just fund other symtom. Iv'd been running the amp for at least
3 hours when all of a sudden the right channel made a crackling sound. sense
that the right channel volume went down. until now I'm trying to figure it out. the left channel is 80% louder than the right channel. I will appreciate any advice I can get. thank you very much.
Thanks Bifwynne, I will give him a call at ARC.
Torogi, if you really want to keep the amp, I strongly recommend at this point that you send it back to ARC for evaluation and repair. It is well known that ARC fixes everything they ever sold. I'm not an electronics techie, so I can't say whether your problems will be costly or not to fix. Who knows, maybe some old passives (e.g., caps or resisters) are bad. I believe that the D-76A was built in the mid-70s, so it could be 35 years old by now. Perhaps Hifigeek can weigh in if he has any ideas, especially what could be wrong and how much to fix. Good luck.

Well you could always send it to me as well if you are close to the west coast. Actually, I have refurbished quite a few D-76A's in my time and in fact when the amp is done, it sounds better then new. The reason is, all the filter caps are replaced with non-twist lock caps. The twist locks that came standard with that amp have high ESR (equivalent series resistance) not a good thing for a filter cap to have. Unfortunately, that was all that was available when that amp was manufactured. All the new caps have little adapters so they fit in the circuit board spaces for the twist locks. Also, there are a number of zener diodes used as voltage references, and those tend to drift over time. When the amp is finished, and retubed, it is one awesome sounding amp. Hopefully, one day, ARC will make a commemorative version of that amp as it's truly a classic. I keep pushing them to do it. I think it's time to ask them again. lol
Hifigeek: I know this is about Torogis' amp, not mine, but I'm just curious about how much it costs to refurbish an old amp like the D-76A. Reason: one day I may have to refurbish my VS-115. Thanks
Dear Torogi,
I don't see where you say you have any problem with how the amp sounds. It is highly improbable that it could operate properly if indeed those tubes were not firing up. It is often difficult to see the glow from a tube; have you looked at them in a darkened room at night? I suspect that you have no problem at all. Or is there something perceptibly "wrong"? If so, what?
Hey Lew, on 4/3/11, Torogi says that the amp has tsouris in the right channel. It seems like Torogi may have bought a refurshing.
I tried turning off the light to see if its lighting up and I also tried touching the tube with my bear hand after two hours of the amp being turned on. I know I'm not suppose do that but I can't stand the fact one of the tube is not working. right now I cant barely hear the right channel so I stop using it. I entent to keep this amp for a long time so I will fix it or have it fix regardless.
I dont know why? may because the first time I use it with my vintage JBL it sounds warm and sweet. before I had that problem. by the way I live in west coast of British Columbia. Vancouver BC. how far are you from BC HIFIGEEK1?
Bifwynne your amp is totally different then the D-76A. I would have to look at the D-76A to see if it's been 'messed' with before I can quote. Also the unit needs to be repaired before anything else can be done to it.
Hi guys, I decided to open up the ARC underneath the transformer and power caps only to found out that there are two 2x 400volts 200uf robycon caps that are added.I assume that the original mallory caps are half dead. this is more problematic than I anticipated. I think I will focus on this one first. do you think it has something to do with the tubes? I took some pictures If you guys are interested I can send some.thanks
Let me suggest you either send it to ARC or to an authorized service facility. Since those are non-standard parts, and the fact that the unit runs at high voltage, I really do think you would be best served by getting it repaired by people who know all about the unit and ARC in particular.
Given the age of this amplifier, I would definitely have someone thoroughly check it out. It is not just a matter of the tubes. I had two of these amps in the early 1970s! I am surprised that you have not blown a fuse.
I think the D-76A has a line fuse but not a screen fuse. Do we know if it has the right line fuse in it?
No, nor do we know who told him it didn't matter whether the tubes got hot, nor whether he heard any music, but I guess his using it means that.
I'm not sure whats the deference between the line fuse in the screen fuse. all I know is that the D-76A has a line fuse. its rated at 6 A 250 V How do we find out weather its the right line fuse? surprisingly it never blew. I will try my third attempt tomorrow to call CALVIN at ARC to ask some of this questions.
Torogi, your last post implies that you are having a hard time getting through to Calvin. That is surprising because he is always available, at least when I call. I know he was on vacation last week, so perhaps he's catching up. If you can't get through to Calvin, then try Chris. Chris is the resident techie at ARC. I know that he supports the local ARC authorized repair guy where I live.

Sorry to sound like an old saw here, but I agree with Hifigeek and the others who have recommended that you ship the amp off to either ARC or an authorized local repair tech. I get the sense that you are trying to trouble shoot the amp yourself and unless you have a deep technical knowledge of electronics in general and ARC gear in particular, I think you're literally playing with fire, IMHO. If it was my amp, that's what I would do.
Your not going to get the answers you want talking to Calvin as he is the parts manager. Chris is the tech and he wont be able to really answer you because the unit is not in front of him. I can look and see what the fuse is supposed to be but that still wont solve your issue with the tube and the non standard ARC parts that were installed. It will have to go to someone for repair. You can send it to me or to ARC. Either way you will need a shipping carton if you don't have the original one for that amp. The boxes are not cheap but its the only way that amp will survive it's journey without damage.
I did finally talk to CALVIN today. the reason I cant get hold of him cause I think they are ahead of two hours than us + I can only call him during my break time at work. The fuse is 5 amps 250 volts not 6 amps I dont know if it will make any deference. I do agree both fo you 100% its not about replacing a few caps here and there I'll live this matter to the pro. I am being recommended by someone here in our area I am told he fixis vintage gears. he is currently working on a CLASSIC 60 ARC right now. to me thats a good news...this will save me shipping cost. I will be visit him sometimes this week. Worst come to worst I will send it to ARC or to HIFIGEEK.