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Discussion Starter #1
I've been playing this amp regularly for several hours a day without issue.

Suddenly, this morning, it's dead. No sound at all.

I took a look at the tubes, and only the rectifier tube is lighting up. It's rather on the hot side too, but maybe that's normal enough, I don't really know.

None of the heaters are coming on, in the power tubes or the preamp tubes.

There's one obvious fuse I can find, on the back panel, and a continuity tester says that fuse is just fine.

I took a quick look inside the chassis, and I don't see any other fuses that could be responsible.

The heater wires and all their socket connections appear to be intact, and I'm getting positive continuity all the way down that line.

Any ideas?

Should I suspect that the rectifier has gone bad, as a first step?
 

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Discussion Starter #3
PT is a Hammond 290BX.

Expecting 6.3V AC at 3A on the green wires.

Using my super-awesome cheap-as-dirt multimeter...

2.8 to 3.0V AC between each ONE of those green wires and a chassis ground.

6.2V AC if I measure between one green wire and the other green wire.

I checked each tube socket, and if I measure across the heater wires, I see about 5.7V AC at each socket.

So.. I'm wild guessing that this is ok, and the PT is fine.

And now I'm looking for a bad tube?
 

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Discussion Starter #4
SMH. I don't know what to think now.

I pulled each tube and checked for continuity across the heater pins, to see if I had burnt filament or something.

Everything checked out. There was one preamp tube that didn't get a good result at first, but when I checked it again later, it was fine.

Then I put all the tubes back in their sockets and powered up and suddenly I've got heaters again.

Hooked it all up and now I've got sound. The amp seems to be working as normal.

I don't know what to think. Sketchy preamp tube? Would that actually kill the heaters on all the tubes?

It doesn't make a lot of sense to me.
 

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Maybe just a dirty tube socket pin.

Not quite the same, but I recently had reverb "fail". In the end it was the tank input and moving it in/out and some contact cleaner fixed it up and no issues now. That amp and tank were 35 years old. Even aluminum oxidizes enough to open circuit.
 

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If they were all out (except rectifier), then a bad connection somewhere between the transformer and the first tube that gets supplied.
Assuming this is the re-issue? If they are wired like the old ones, maybe at the pilot lamp socket?
 

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Discussion Starter #7
Not a reissue. This amp was born in 1965.

Weird thing is that I was getting continuity on the heater circuit all the way from the pilot lamp to the end of the string of heaters. I checked every tube socket.

I didn't try that with the tubes pulled - maybe that would have show me a problem.

It's working now, I'm just not sure I can trust it.
 

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It's funny I have a canadian jcm 800 and I went to play the other day and turned it on and got no sound. Took a look and the preamp heaters werent lighting up. Checked for continuity across the heater socket pins found no issues. Cleaned the tube pins and sockets with de-oxit and the heaters came back. So far so good. on top of the previously mentioned suggestions, hows the tension on your tube sockets?
 

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It's been a while ... hopefully all is still well. No drop-outs or weird other noises ?
Your rectifier is on a different (5 vac) winding , right ? (yellow leads) so don't suspect the rectifier just yet. It has nothing to do with 6.3 vac.

I'd be doing some gentle vibration tests on the tubes. Gently tapping on the tubes with like the rubber end of a pencil.
If there are any jumpers/connectors in the 6.3 vAC signal path, certainly re-seat those.
I don't believe there is a CT on 6.3 heater winding ( anywhere I've ever seen ), just for 12.6 and that doesn't apply for this tranny.
Opening any tube to socket heater connection should not cause loss of heaters with the exception of the one affected tube.

Follow the twisted 6.3 heater wires to make sure its not strained or stressed against any component, i.e. well isolated from contact anywhere.
As far as reliability, I might suggest have your output tubes (or all ) checked (leakage) and/or have another set of op tubes handy.
 

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Discussion Starter #12
I opened it up again after it had miraculously started working again, and I was poking around the spot where the heater wires meet the pilot lamp when I noticed a huge glob of solder rolling around loose in that corner of the chassis.

I have to guess that was the problem. Totally random. It was big - like a chunk of split shot that you'd use to weigh down a fishing line.

Best guess is that roaming glob of solder had been shorting the heaters to the chassis somehow, just randomly, sometimes. I fished it out and it's all been fine ever since. At least so far.

Thanks all for you advice :)
 

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Discussion Starter #14
Well, I'm bewildered, but this problem has come back.

The amp has been sitting unused for almost a year. Unplugged too.

I'm starting to wonder if it could be a capacitor problem? Unfortunately I don't have a variac to 'reform' the caps.

I haven't tried anything yet; haven't even pulled the chassis yet, but I'll get to that stage soon.
 

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6.2V AC if I measure between one green wire and the other green wire.

I checked each tube socket, and if I measure across the heater wires, I see about 5.7V AC at each socket.
Was that 6.2VAC between the greens with all the tubes installed? Yet it's down to 5.7VAC at the sockets? See if you can find where it is dropping the missing .5V, you may find some kind of intermittent connection.
Is this an original 65 Blackface Deluxe Reverb?
 

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Discussion Starter #16
Was that 6.2VAC between the greens with all the tubes installed? Yet it's down to 5.7VAC at the sockets? See if you can find where it is dropping the missing .5V, you may find some kind of intermittent connection.
Is this an original 65 Blackface Deluxe Reverb?
Thanks. I'll pull the chassis soon and see what I can see.

It's a 65 Deluxe. There is no reverb in this amp.

It is a real 1965, although I wouldn't call it "original". It has certainly been messed with in the past. And later "restored".

Some of the parts are not original. The output transformer is definitely a replacement, and there's a 4, 8, 16 ohm selector switch on the back panel beside the speaker jack. There's a three prong power cable, and the ground switch on the back doesn't do anything any more. One of the pots in the Vibrato channel has a switch at the zero position that hard-bypasses the whole Vibrato circuit. I don't think the accessory plug is connected to anything. Aside from those changes I think it's pretty close to the original circuit now.

I'll try to grab some pictures later.
 

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I'll share a similar one with you that is probably not the same but might offer some insight. Heaters take a fairly hefty current and need a real solid connection. A connection can look pretty good and the current can flow and then just quit. Sometimes it's easier to just go through all the heater connections and resolder them.
I had a re-issue that the owner said had been in for repair elsewhere several times and always came back and worked awhile, then quit. Turned out that one of the spots where more than 1 heater wire goes into the socket pin, the top (visible) wire was soldered but the one underneath was not. Right from the factory. It worked because the other soldered wire was holding it in there fairly snug. But sometimes it just couldn't carry the current and would cut out. You could pull on it with pliers and it stayed in place, but there was enough wiggle room for it to be very occasionally intermittent. I got lucky with that one and sure couldn't fault the other guys for not finding it.
 

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Good point JB. Re-soldering all the filament connections as a matter of course is not a bad idea in these old amps. Solder will crystallize under fairly heavy current and over time. There may be enough resistance at the joints to cause a significant voltage drop, or a bad connection.
 

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Discussion Starter #19
Thanks guys. I really should have spent more time on this when it happened a year ago.

I'm pretty sure that .5 V drop was happening between the pilot light and the first tube socket, so I'll focus in that area first.

I just need to find the time and energy. Way too exhausted last night because Monday.
 

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Discussion Starter #20 (Edited)
Getting some pics together so you can see what I'm dealing with here:

Deluxe_basics.jpg trannies.jpg

I'm guessing that choke is original, although the PT and OT both seem to be replacements.

I haven't found a date code de-coder to tell me what 606-5-39 means, but I did get some google hits showing the same code on some Hammond components in a 1965 Vibrolux and a 65 Princeton Reverb.
 
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