Bugger -- time to take apart the Deluxe

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pstamler

Well-known member
Joined
Jan 24, 2005
Messages
1,509
Location
St. Louis, MO, USA
Well, my old reliable blackfront Deluxe is finally showing its age. Tonight at the gig I was running the acoustic through it and all of a sudden the volume dropped way back. "Hell's Bells", says I, "The damn acoustic's battery has done crapped out again." So I switched to the ASAT (neo-Tele), and it was intermittent; if I put my foot on top of the amp it would get loud and clean, then a few seconds later drop back down.

That was on channel one; channel two (tremolo) doesn't work at all. I found that the tube shield was missing on the input tube. When I got home I tested the tubes and all but the 12AT7 were fine; I replaced the 12AT7, replaced the tube shield, fired it up...and it was the same. So I guess tomorrow I need to take it apart. Sigh.

Is this a common failure mode? Any off-the-cuff guesses? I'm thinking maybe bad connection to a coupling cap someplace. Or a leaky coupling cap...but none of them, I think, are the originals. I think they're all one or another kind of film. [EDIT: Exercising the pots made no difference at all.]

Peace,
Paul
 
AB763 circuit?

I'd suspect output tube sockets. They fail in Fender amps frequently. Check the output tubes too. If it's a real old black face and it hasn't had a cap job, you ought to bite the bullet and replace all the electrolytics. I'm curious about the vibrato channel not working at all. Usually it's the the roach that fails. but that kills the tremelo only, not the signal. Fenders are pretty easy to work on and always worth fixing.
 
I'd say an age or heat related component failure ,
maybe solder joint
but if it's that intermitant and you can make it work ,
hopefully not hard to find once you tap & wiggle inside
with some signal
but sorry no known common issues to me [ i 'm not so lucky ]
sometimes the plate resister go noisey

for a guy like you shouldn't be hard , won't curse ya

good luck & skill
 
Power tubes are good? If so, check the trem circuit. But I think there's something in the output section.

Buttery pretty much nailed my thoughts. Make sure all caps are bled, and I'd reflow the solder on all the tube sockets. Also, lok on the board, there are usually tons of suspect solder connections just due to age. You should reflow all that at this point.

It'll be easy and you'll be back up in no time. :green:
 
Do you like Chinese food? Use a chopstick to probe each wire/component while running signal. You may find a wire or component lead going into a hole in a solder blob. If you do, remove that old solder, and resolder it good. easy fix.
 
Non-reverb Deluxe, right? Kinda strange that one channel is dead and the other is intermittent like that since there's no sharing of tube halves between channels. Maybe one of those old carbon comp resistors has fractured. Tap with chopstick while amp is on--a bad one will be evident when you hit it. Don't forget the ones in the doghouse Re-tension all the sockets while you're in there, too. I'm sure you'll have it up and running in no time.

BTW, in case I didn't say it before--thanks for all the help and suggestions you made when I was working on my SFDR and SFVC this summer. They both sound fantastic now.

A P
 
[quote author="AnalogPackrat"]Non-reverb Deluxe, right? Kinda strange that one channel is dead and the other is intermittent like that since there's no sharing of tube halves between channels. Maybe one of those old carbon comp resistors has fractured. Tap with chopstick while amp is on--a bad one will be evident when you hit it. Don't forget the ones in the doghouse Re-tension all the sockets while you're in there, too. I'm sure you'll have it up and running in no time.[/quote]

I'm sorry, I wasn't clear enough in my original posting. The tremolo channel's been out for months, probably a bad cap or solder joint. The intermittent stuff is the new feature.

BTW, in case I didn't say it before--thanks for all the help and suggestions you made when I was working on my SFDR and SFVC this summer. They both sound fantastic now.

Glad I (we) could be of help.

Peace,
Paul
 
pstamler said:
[quote author="AnalogPackrat"]Non-reverb Deluxe, right? Kinda strange that one channel is dead and the other is intermittent like that since there's no sharing of tube halves between channels. Maybe one of those old carbon comp resistors has fractured. Tap with chopstick while amp is on--a bad one will be evident when you hit it. Don't forget the ones in the doghouse Re-tension all the sockets while you're in there, too. I'm sure you'll have it up and running in no time.

I'm sorry, I wasn't clear enough in my original posting. The tremolo channel's been out for months, probably a bad cap or solder joint. The intermittent stuff is the new feature.

Hey pstalmer;
AnalopPackrat is on the track here: Here's my list in order to maybe help out quickly.
1) Check your tubes and sockets first; this might be solvable without removing the chassis. use known good tube to figure out which tube may be bad or intermittant. Retension your tube sockets as AP said.

2) If it's an oldie as implied check the 1.5k preamp cathode bias resistors or better yet just replace them if original. Replace the 25mfd/25v cathode bias caps unless you have done so already lately.

3) If not already done replace your 470 ohm 1 watt resistors (carbon comp.) on the output tube sockets with high quality metal film 2 watt resistors. This won't solve your preamp problems but it will make your amp more reliable. While you're at it replace your filter caps in the doghouse. Unless of course they have not been replaced lately. Make sure your new doghouse filter caps will fit in the doghouse before you buy them.

4) If # 2 above didn't solve you dead channel or intermittant problems it's time to grab a schematic and a voltmeter and check all your dc and ac votages as described on the schematic. It's likely that if the trem. channel passes audio but doesn't trem. that the neon lamp in the optocoupler has gone bad. You either replace the lamp with an NE2 after cutting the shrink tubing away(save and reuse it if you like-just put a few wraps of black electrical tape over it when you're done) or buy a new opto from newsensor or someone.

5) Since you gigging you probably should do all these repairs for reliabilty's sake.


good luck
gb
 
When I work on equipment that is older and been well used I often test every part I can when I have it apart. Often in an older guitar tube amp I will test all the caps(value DA ESR and leakage) and resistors and inspect the tube socket connections and check solder connections like others have posted.
It can be a drag but tube guitar amps often don't have many parts.

FWIW A laney vc30 had an intermittent problem. I changed some tubes in it and the problem started. It turned out one china made 12ax7 I removed had fatter pins and had expanded the socket metal enough so the replacement tube pin(s)did not make good contact. I measured the pins with a dial caliper I don't remember if I saved the notes. I am not sure if it was the fatter pins or maybe weaker metal in the socket that was the cause of the problem.
 
Well, I opened it up. In addition to the dubious 12AT7 I replaced the 0.1uF cap in the Normal channel tone stack, since it made very nasty noises when I tapped it with a wooden spoon (didn't have any chopsticks; I like Chinese food but usually at House of Wong or Hunan Wok, not take-out). The intermittent problem didn't go away; I could make it cut in and out by moving the plug in the jack slightly, so I thought I might have a bad jack, or it might have a bad ground. Messed with that, still cutting in and out.

While it was open I sprayed a bunch of CaiLube in all the pots of the Tremolo channel. That solved the dead-channel problem; they must have been really filthy. Anyhow, that let me verify that the intermittent problem happened with both channels, not just one. Finally I narrowed it down: intermittent contact in the 12AT7, the phase splitter tube. I found a position which works, but re-tensioning is a little dicey, so I may just pull the chassis again and replace the whole socket. Meanwhile it's back together and sounds delightful. I had to quit working on it because I ran out of time, but at least I know where the problem is and what to goose if it acts up again.

Oh, when I do the new socket (or retension) I'll replace a few more bypass caps. The main caps have long since been replaced with a couple of whopping big computer-grade cans. I'm pretty sure all the resistors are metal films by now.

Thanks, gang!

Peace,
Paul
 
Although a bit light perhaps , pencil with eraser works well too

way to go Paul , knew it wouldn't be much for you

Just out of curiousity , have you ever changed anything that made
noticable difference in tone [ including tubes ] that you could tell
 
Putting the big capacitors into the power supply certainly tightened up the bottom and increased the headroom -- no classic "Deluxe sag" on this amp. (When I want sag, I use the little Kalamazoo.) When I did the mods, I was also using the Deluxe for bass (with an external bass speaker, not the internal one!) At moderate volumes, it makes a really nice little bass amp. The metal film resistors, in addition to lower noise, cleaned up the attacks and brought out a lot more detail. This Deluxe begins to sound a bit like a Twin. Which is good for some of the stuff I do, but I'm more likely to use the Kalamazoo most nights, as I want a little more dirt. At this particular gig, the Fender was there as a backup, and got pressed into service when we needed the Kal for something else.

I haven't done any real tube-rolling; the outputs are a couple of GE 6V6s that have been in there a long time but still keep ticking; the input tubes are mostly Telefunken ECC83s that I got back when they were the standard stock 12AX7 equivalent at my local distributor (yes, there was such a time). As usual, the driver/splitter tube and the rectifier are the first to go.

Oh yeah, I also added a direct out to the Normal channel, switchable to pre- or post-volume control. If I run that (set to pre-) to the input of the Tremolo channel, it stops being clean and starts being real dirty. Don't know whether I like that brand of dirt or not, though.

Peace,
Paul
 
If you have an intermittent tube socket, I'd really recommended taking care of that right away. Also, if your caps are fully bled, retentioning shouldn't be that hard. Certainly easier than changing the whole socket! Just check every pin with your volt-meter making SURE you've got a good ground to get accurate readings. Then use a little wire (I like the real tiny screwdrivers).

Take care!
Joel
 
Here's a great place for NOS gtr amp stuff.

www.angela.com

I just did a '65 Bassman tube sockets and verified Plate resistors. Owner couldnt be happier.
 
i know exactly what it is, but i suck.
so a cant tell you.,
i am no longer allowed to post in the brewery.
:green: :sam: :!: :razz: :razz: :razz: :oops: :oops: :?


Oh, put in a grid stopper.....


:green: :green: :green: :green: :green: :green: :green:

if a doug fir kills your wife, you should have used a grid stopper...
:green: :green: :green: :green: :green: :green:
 
Well, nuts. Last night I opened it up again and retensioned the wonky tube socket. Also did a wiggle-inspection for bad solder joints, didn't find any. It worked fine on the bench, with tone. I put the shield back on; still fine. I put it back together, started playing, and after about 15 minutes it started crapping out. Each time it crapped out I could get it to work by touching the 12AT7 a bit, which would last for a little while and then crap out again. Yes, I've replaced the 12AT7 tube.

Like I said, nuts. I'm weighing whether to resolder all the 12AT7's connections, or just go whole-hog and replace the socket, which is a pain in the butt.

Ideas?

Peace,
Paul
 
And by retensioning you mean , bend the metal receptors on the socket
in , so as to make a better contact and grip ?
And no sign of contamination between socket pins ?

if you had to take the chasis in'n'out a few times , might as well put a good socket in there
 

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