Super Reverb fuse blowin

[AtomicMassUnit]

I have a super reverb here that has a little problem I'm having difficulty locating. It was blowing fuses, so I pulled it open and it had some caps spewing, so I did a cap job. I replaced the fuse, pulled out the rectifier and power tubes and fired it up. It was cool. I put the power tubes (new, known good ones) and fired it up, and it blows the fuse. I checked and I have bias voltage. I don't see anything wierd other than pin 3 of one of the power tubes obviously had arced out to pin 2 on the old set. I figured, OK, it blows fuses but only with the power tubes in, and it's not the tubes, it might be the OT, so I subbed in a good one. Still blows the fuse. The choke measures 104 ohms. What else could it be?

[Bruce / Mission Amps]

Probably still the socket regardless of tubes in or out, replace it.

[Enzo]

What does it do with the rectifier in place but no power tubes? If it holds a fuse without tubes, then the choke is not bad, or it would blow fuses anyway. If it blows with the recto in place and no powr tubes, I immediately wonder if you got a filter wired backwards. Remember those two main filters are in series, so if ALL the caps in the box are facing the same way, that might be the problem.

With it running, check the voltage at pins 3,4,5 at EVERY power tube socket. SHould see B+ and 3 and 4 and bias at 5.

Now add ONE power tube and fire it up. Does that work? If so, try it in each socket. If one socket blows fuses, then something there is bad. Now try each of the other tubes one at a time in some socket. Just because they are new doesn't mean ther isn't a bad one. If all four tubes are OK, and each socket works, try three tubes leaving the socket where the tube arced empty. Does it hold? Now add the fourth tube. If it blows, try turning out the room lights and watching the sockets closely for a tiny telltale spark as the fuse blows.

Arcing is like poison, once it infects the socket, the socket may have the problem forever. Might replace that socket.

And for that matter, what fuse are you using? Is it really the correct fuse? You are using a SLOW blow?

[AtomicMassUnit]

With the rectifier in place and no power tubes, it wasn't blowing the fuse. Filters are wired correctly, I've done about a million of those, but double checked anyway. I'm using 2a slow blows. I just turned it on without power tubes and left it for a minute or so, measured B+ (475) on pin 3 and 4 of the socket that didn't look arced out, and -43 on pin 5, and when I went to check pin 3 of the arced socket, the fuse blew, this was the first time it blew with no power tubes in. I think you're right about the socket being the culprit here, because everything else seems ok. I gotta get some more fuses, swap the socket out, and see what happens, because that was my last one. I'll report back (late) tomorrow night hopefully...

[AtomicMassUnit]

I replaced the tube socket and fired it up, it didn't blow the fuse. I can hear hiss when I turn the volume knob up. I'm going to wait until in the morning when I can make some noise to really check it out though and make sure everything else is ok. Thanks for the tip, I had no idea the socket itself could be bad.

[Enzo]

I don't believe there is ANY part that can't be bad.

[AtomicMassUnit]

In that case I'm going to ask for your help once again fixing this Princeton Reverb that has a super mysterious problem. I sent it to a real tech and he couldn't fix it, and I've had a go at it many times. I'm gonna start a new thread...

[ken]

Change your power tube socket... when you arc a socket, the burned bakelite chars into carbon, which is what resistors are made of. The socket will always arc, and no amount of cleaning you can ever do will fix the socket either.

Ken

[R.G.]

Never willingly put in a bakelite socket. Ceramic is much more sturdy, and is not prone to arcing problems.

[AtomicMassUnit]

Thanks so much you guys! problem solved.

[Doc Stitches]

My Fender Super Reverb is blowing fuses ( within one or two minutes ) ONLY when the tubes are in. One GL6 gets VERY red ! One of the preamp tubes is not coming on at all. Are these the culprits?

Can you tell me about this amp? I can't find one like it anywhere. It is a head only, .... no speaker cabinet.

It has 11 knobs, the master volume is a push/pull so I assume it was made after 1973? The main transformer has 606-504 on it, and A7631 is stamped on the back of chassis. It is 45 watt. Is this a true point to point amp design? Also, this amp has not been used for about ten years and the main caps are Mallorys. Shouldn't they show some voltage after the amp being turned on today for the ( 2 minutes ) I was testing it?

Thanks
Jim

[R.G.]

One GL6 gets VERY red !

Mother Nature is trying to tell you something there.

That tube has lost its off-bias. Swap the tubes and see if the redness follows the tube or the socket. If tube, you have a bad tube. If socket, you have a problem in your bias connections to the tube and are not getting the off-bias on the grid.

One of the preamp tubes is not coming on at all.

That's a problem, but a secondary one. Fix the hot power tube first.

Is this a true point to point amp design?

No. Tagboard is not point to point in any significant sense.

Also, this amp has not been used for about ten years and the main caps are Mallorys.

The caps may be bad and leaking so much they cause the fuse to blow.

If the amp has not been used for ten years, save yourself a lot of grief and just go replace all the electrolytic caps now. It's not worth the wear and tear on you to let them all fail one at a time, perhaps taking a power transformer with them.

[bnwitt]

I agree with RG. A complete electrolytic capacitor replacement is in order for that amp including the main filter caps under the cap can. I would do that before anything else. Obviously the amp has had some service in the past as evidenced by the newer bias caps and the ceramic socket.

[Doc Stitches]

Thanks R.G. and bnwitt.

Would you recommend a good place on the west coast to buy / order these caps, ceramic sockets, and tubes ?

I am in the San Jose area.

Thanks again
Jim

[bnwitt]

Jim,
I don't know of any vendors on the west coast. I'm sure there are plenty but I buy most of my stuff from online vendors across the country. Antique Electronic Supply is in Arizona and has very fast delivery to the west coast(I'm in Riverside county and get my parts usually the next day with just UPS ground shipping). Here is their website:

http://www.tubesandmore.com