Help diagnosing Fisher 500C issue

About six months ago, I bought a pretty much fully refurbished Fisher 500C from a seller on Ebay--he had excellent feedback on similar auctions and has done more of this since. Repairs included a full complement of new tubes, changing caps, some thingy regarding the on/off switch and so on. I don't remember it all, but it seemed very thorough.

I have had no problems since then, until two weeks ago, when I played the unit pretty loud for maybe six hours (driving BA-150s). At some point late in the evening, one channel failed, so it was essentially a mono amp for the next hour. (Hey, the party was rockin', so I wasn't about to stop the music, though I did turn it down a little.)

I was worried about permanent damage, but the next morning, both channels powered up fine--no problem whatsoever. Guess it just got a little overheated.

However, since then, I have heard a relatively loud pop twice when playing records. Both times I was in the next room, so I don't know if it was in one channel or both. No magic smoke release, nor any weird smell. SQ seemed unchanged afterward.

Any idea what might have caused these two pops, and if it's something I need to address?

 

Leaving it running with a channel out is a gutsy thing to do.
What if one of the speaker wires came undone and you were running that channel with no load?

I'm glad both channels still work.

 

Check the space expander jacks. Sometimes they get pushed in too much and short out a channel.

 

Yes, those SpaceXpander jacks do need checking. Those can and have caused intermittents.

 

Thanks!

Checking the connections was the first thing I did!

 

A cold solder joint anywhere can cause intermittent pops. I'd check the tube sockets first. Have you swapped out the tubes just to eliminate the simple things ?

 

Possible causes of the pops and failure of one channel when the amp heats up are infinite, but could be as simple as a bad tube. Do you have JJs in the power section? These fail notoriously. Verify your speaker and interconnect connections are solid and play the receiver again for many, many hours. Check frequently for glowing plates in the power tubes. See if the channel fails again and report back. While doing so, play the phono section and see if the pops occur again and if they are in both channels or just one. Before powering up the unit, remove the two 12AX7s from the phono stage and re-insert them. This should have the effect of cleaning the tube sockets. For the record, no pun intended, when you experience a problem with a vintage tube amplifier such as losing a channel, abnormally loud noises that aren't part of the music, or glowing plates, the WORST thing you can do is continue to operate the amp. Shut it down immediately and get it to a competent technician. Check the fuse also to make sure it's the right value while you're at it. Good luck.

 

Update:

I took it into a tech at Brooks Berdan, a well-known hi-fi shop in the LA area.

It turns out I'd fried three out of four output tubes. I guess it was from the hard driving from a few months ago.

He replaced the tubes and did some other minor things. But when I took it home, there was a persistent hiss in the right channel, no matter at what volume level or input selected. I took it back in, and he said that I had a failed output cap. (Or maybe it was a filter?) In any case, he said that replacements cost $62. Problem is, since they are a PITA to replace, he'd have to charge me an hour's work (he said he normally charged two, but would make an exception in my case). So that's $167 in parts in labor on top of the $202 I already spent AND the $600 or so I originally paid for the refurbished unit in the first place. Given all that, he said he'd buy back the tubes from me, in essence giving me a $150 refund, and not make the repair. Then I'd be out about $650 or so, instead of keeping pouring money into this thing. (There are three other output caps that could also fail.)

I'm ready to take him up on his offer and get an Outlaw RR2150 or something instead.

Any thoughts on the matter? I need to call him back today.

 

Get the repairs done. In the long run, it's worth it.

 

Yeah, but is this the unit to do it on? If I get the repairs done, I'm in $800. If another output cap fails, I'm out another $167, getting me close to $1000 all in. What's the likelihood that would happen?

 

My suggestion would be to not have a high end shop do the service - they will charge you high end rates. A single cap replacement shouldn't cost $167.

Follow my earlier suggestion and contact one of the guys on AudioKarma, ie: dcgillespie, audiodon, larryderouin, etc. In fact, audiodon (who fortunately lives nearby) completely went through and tuned up my 400, and he even upgraded some parts, and the work cost me not much more than you paid for that single cap replacement. They might even be able to refer you to an affordable, qualified tech on the west coast.

http://www.audiokarma.org/forums/forumdisplay.php?s=&daysprune=-1&f=172

 

Something is not right here. Those output tubes are pretty tough. Just playing them loud should not blow them(what brand were they, and how do we know they were new other than what you were told?). I have original Fisher 7868's in my Fisher 400, and original 7591's in my X-101-C. Those units are both restored, but both are from the early/mid 60's. Unless the ones you had were crap, they shouldn't blow in 6 months, especially 3 at a time. Which means that the guy you bought it from perhaps didn't do all that he said he did, or did a lousy job, in which case you should be speaking with him.

Next, while I have heard nothing but good/great things about Brooks Berdan(including from our host) I'm not crazy about how they handled this. When you brought it in why didn't they find the failed cap right away. A good tech would assume that their has to be a reason why 3 tubes would fail. Did they offer you chance to have the whole unit inspected and you turned them down? If so, well, then you're on the spot. But otherwise the way you're describing it sounds pretty shoddy to me.

The 500C is a great piece, and given a complete restoration by an expert tech it will last another 20 years minimum. But it's pretty obvious that you have yet to experience that yet. I have no experience with BB, but I would say if you do go that route find out what a complete going over will cost, what it will include, and what they will warranty. And also tell them what the Ebay seller claimed to have done and get their thoughts. If it can be proven that he did job less than what he described you might have a case against him.

In any event, you have a great piece worth keeping if fixed properly. Paying $1000 is a bargain for them. You might also want to go over to the Fisher forum on Audiokarma and get their feedback(where btw there are some great restoration experts).

Good luck.

 

The output tubes were JJ's, and the eBay seller who restored the unit said they were new. I have no reason to not believe him--in any case, they weren't originals and in fact all the tubes in the unit were new JJ's. I've read mixed things about them, but that's what Brooks Berdan replaced them with--JJ's, although this time they were quite a bit more expensive than, say, on Amazon, because Brooks Berdan sources them from someone who supposedly meticulously matches them.

When I took the unit in initially, I gave them cart blanche to do whatever. I was hoping they'd give it a full run-through. I'm not sure if they did or not, though I supposed they did. If they gave me a reason why the tubes failed, I don't remember it. (Keep in mind that this was done via a phone conversation the past month has been a blur for me, with a lot of travel, work-related and otherwise, and resulting catching up to do. My short-term memory is largely shot.)

I guess what I should do is get him on the phone again and ask him for a complete list of what he did via the first round of repairs, and get his theory for why the output tubes failed, just so I have his assurance that it won't happen again as well as a record of what work was done. Then I should see if I can get an AK member who might be able to help and give me a quote. After I've got that, I should be able to decide whether to a) stick with BB, b) go the AK route, or c) ditch the unit and get a NAD!

 

www.eurotubes.com was the likely source... plus BB added their own markup on top.

You should always retain detailed records of what work was done on your amp. It helps the next tech figure out what needs to be done.

 

JJ 7591's have a poor rep . They've had a pretty high rate of failure. For reissues EH 7591's are better tubes.

 

I was told that they are too big to fit inside a wooden Fisher case, though. Right?

 

My guess would be the large can capacitors. Those things always go bad on vintage tube amps.

 

Something about this repair tech is not sounding right to me. It seems like they are making guesses...and charging you for their wrong guesses. I suggest you follow action pact's advice and get some help from the Fisher discussion board at AudioKarma. They will steer you in the right direction.

 

That's what I've heard. But your choices for new 7591 are pretty limited. I'd get a quad and then search around until you can get a quad of NOS Fisher's that it's in your price range.

 

According to Stereophile's review:
http://www.stereophile.com/content/fisher-500-c-vintage-stereo-receiver-page-2

"Until recently, you had to buy used or NOS (new old stock) 7591As, but a new 7591A, the 7591A EH, is now being manufactured in Russia by Sovtek under the Electro Harmonix label; four can be had for less than $100. It's a bit bigger than the original, but it still fits the 500-C's sockets and inside its handsome wood cabinet."

My 500c cabinet isn't an exact reproduction, but I do have to take out the Electro harmonix, before I slide it in and out of the case, I think if you take out the tubes before sliding the receiver in and out, they should fit