Bugger -- time to take apart the Deluxe

[Mbira]

give it a good cleaning in the preamp tubes. a good solid connection with dirty contacts won't do you any good. I have never actually seen a bad socket-except in power tubes that arch, but I know it can happen. Clean it first.
Good luck!
Joel

 

[Mbira]

I give one quick spray direct into the socket and then push the tube in and out a few times to get the contact cleaned.

 

[Flatpicker]

[quote author="pstamler"]...I put it back together, started playing, and after about 15 minutes it started crapping out...[/quote]
Maybe heat related? It gets a lot warmer it there when its stuck in the cab, so could be a component going south when it heats up.

 

[pstamler]

[quote author="Flatpicker"][quote author="pstamler"]...I put it back together, started playing, and after about 15 minutes it started crapping out...[/quote]
Maybe heat related? It gets a lot warmer it there when its stuck in the cab, so could be a component going south when it heats up.[/quote]

Uh-huh, my thought too -- but touching the 12AT7 makes the problem go away for a minute or so, after which it comes back.

To Greg: yes, I used a tiny screwdriver to bend the contacts for more pressure on the tube pins. No sign of crud between the pins. And the tube's been in and out of the socket a dozen times already. The preamp tubes, meanwhile, are fine, no problems as far as I can tell.

I wonder whether it's a solder problem after all? Maybe it's time to redo the solder joints anyway, just so's I'll know.

Peace,
Paul

 

[guitarbill55]

Yo, just replace the socket(s) with the gold plated ones; you'll be happy!
Also replace all the resistors, capcitors and wiring associated with the12AT7. You'll be happier. :green:

gb

 

[okgb]

Eliminate the possibility with a new socket , if you're going to redo the solder joints anyway ?
there aren't parts soldered directly to the socket right ?

I've seen where caps have leads that loosen up and can
actually change the gain as they are moved , but
I second the above opinion about looking at whatever is connected or
touching that socket , if it's wires following them to the next component
or , you cover the shipping and i'll take the headache off your hands , ha!

But if it totally cuts out , you can touch it from the bottom and see if anything moves while it is open ?

 

[amorris]

OK...... do not post again... until.... you spend <$5 each on NEW TUBE SOCKETS!!!!!!!!!! angela.com......

while open, look for cold solder, overworked plate resistors, cathode resistors.

 

[pstamler]

[quote author="amorris"]OK...... do not post again... until.... you spend <$5 each on NEW TUBE SOCKETS!!!!!!!!!! angela.com......

while open, look for cold solder, overworked plate resistors, cathode resistors.[/quote]

It's not the <$5, it's the PITA of much desoldering. But I see your point.

[quote author="greg"]But if it totally cuts out , you can touch it from the bottom and see if anything moves while it is open ?[/quote]

Nothing does.

Peace,
Paul

 

[Mbira]

My advice again, is spend $0.0002 on spraying the tube socket with contact cleaner first to see if that works, by golly! Changing tube sockets is a PITA-especially if 20 seconds of cleaning takes care of the problem.

THEN, if it doesn't work, reflow all the solder going to the socket. Go easiest to hardest...

 

[guitarbill55]

If you clean them and don't bother to replace-- you'll probably wind up regreting it at the gig.

good luck

gb

 

[Mbira]

Seriously?!? You guys all replace your tube sockets when you have those symptoms? Man, no wonder tube sockets are getting more expensive. :roll:

 

[Flatpicker]

[quote author="pstamler"]Uh-huh, my thought too -- but touching the 12AT7 makes the problem go away for a minute or so, after which it comes back.[/quote]
Hmmmm. Maybe a pin socket is just loose enough that the heat expansion finishes it off. Sounds like re-soldering and/or replacing the socket would be the next thing to try. Hope you get it fixed. Those sure are sweet amps!

Funny, with all the "acoustic" guitar amps available these day, I still prefer playing acoustic through a good tube amp. Doc Watson still plugs into a Fender Twin Reverb, so looks like we are in good company.

 

[okgb]

Ah c'mon Paul's not a dumb guy , but if the problem is this pesky ,
and uses up this much time , might as well eliminate issues one at a time
and not look back ,
Noe that other rumor about Paul being dead ........................well
turns out just to be a heartattack

 

[pstamler]

Not dead, and this particular Paul hasn't had a heart attack yet (knocking loudly on wood).

I'm vacillating because taking the chassis out of the cabinet is enough of a pain that I really don't want to do it extra times. So if I'm going to pull it, I'm going to do the whole shebang and just replace the socket and be done with it.

So...amorris recommended tube sockets from angela.com. Checking their website, I see two possibilities, p/n 90115 abd 90116. Any preferences?

Peace,
Paul

 

[Gus]

Paul if you tightened the socket and you still have the problem maybe what CJ posted has a hint(grid stopper) you touching the tube and it working. The socket might be OK. If you do open it I would check the PI section with a scope.

What is the condition of the power supply cap at the PI node of the power supply? Has it dried out?

IMO For some of the posts in this thread Just blindly changing parts is a HACK way of fixing things.

IMO Paul knows things about tubes and circuits did you ever read his
tube preamp article in glass audio?

 

[Mbira]

[quote author="Gus"]

IMO For some of the posts in this thread Just blindly changing parts is a HACK way of fixing things.
[/quote]

Exactly my point. I know that I'm not nearly the tube amp guru that a lot of folks here are, but I've done a few hundred amps at this point. I have never seen a tube socket go bad (unless an arched power tube situation). I've heard about it, but to me that's like breaking a fork. I could happen I guess, but pretty unlikely.

Thanks for the reminder there Gus about the grid stopper.

 

[pstamler]

The reasons I doubt that the problem is oscillation:

1) While touching the tube restores normal operation, it typically *stays* restored for 30 sec. or so.

2) It doesn't manifest itself as distortion or funny noises, but rather as a 20dB or so level drop.

3) It's the same with different 12AT7s.

The other possibility, aside from a bad socket, is a broken wire going to the socket.

Peace,
Paul

 

[amorris]

as far as 90115 andn 90116, it looks like the same part, 115 new, 116 new old stock. I would say 115 new. If i were rebuilding for customer, ask new or NOS. $9 each. do it. I would not trust a spraying fix in this situation. maybe as a test, but I would replace a socket just for fun! no really, I cant tell you how many times Ive had to finesse a tube so the heaters fire- sockets, and so on.

 

[guitarbill55]

[quote author="Mbira"]Seriously?!? You guys all replace your tube sockets when you have those symptoms? Man, no wonder tube sockets are getting more expensive. :roll: [/quote]

When the problem keeps reappearing and the cutomer's going nuts; yes I do. A ten dollar socket and a handful of small parts for a vintage amp is cheap insurance that the problem will go away and stay away.

If you think it's hard changing the parts; think about it failing again when you need it. It's a cakewalk. :wink: Do it. :wink:
gb

 

[Flatpicker]

[quote author="Gus"]What is the condition of the power supply cap at the PI node of the power supply? Has it dried out?[/quote] I was originally thinking an old dried cap was crapping out when heated up, but throw a "touchy" tube in the mix, and looks more like a mechanical issue now - especially since it works fine for 30 secs and then craps again. Call me hack if you want (that was my late granddad's name, so I'm used to it :wink: ) but still smells like a bad solder joint or socket. Another trick is you can roll the tube pins between your fingers and thumb, lightly pressing them in closer to each other. This will create a tight fit even if the sockets are loose.