Jeepers! Amp go boom!

[Big Al]

I am having a hard time lately. Just got to the point that I can use my arm in a very limited way and thought , while no one was home, I'd fire up some gear and make some noise. I did, but not in the manner i expected.

I am on disability and medical costs have cut down on my gear budget accordingly, in a word I am on a tight budget. So no spending till I catch up on my Christmas spending. Anyway, I plugged a Strat into my Tweed Super clone and there was some crackling that went away. I noticed the Presence control had no effect. Hmmmm?

Then more loud crackling and I noticed SMOKE seeping from the top panel.!!! WTF!!!! I shut it down and shed a few tears. Great, now I have to take it to my tech but it will have to wait until I can spend some dough.

Hoping I can see an obvious bad part? and replace it myself but I am not an amp tech by any stretch of the imagination, so most likely it is into the shop it goes. So? If I have to take it in what else might I want the Tech to address? I'd like a stronger handle as that thin ass wimpy leather one is just an accident waiting to happen. So fix the smoked part, replace the handle, maybe upgrade the filter caps. Anything else I should consider?

WALLY!!!! CoyotesGator!!!! B Ingram!!!!

Any advise?

I replaced the speakers in my 50's Stromberg Carlson speaker split cab, (suitcase) and now I can't put it together because the magnets are too deep on the speakers so I cannot put the cab together for transport. Anyone know of good speakers that are shallow? Should I look at the Neo Mag stuff? This thing is so cool and matches my 50's Stromberg Carlson AU58B and is the same industrial green color.

luged into my early Bandmaster Reverb and all kinds of noise came out. I am gonna calm down and replace some tubes but the 12AT reverb driver seems to not work, I tried a few, and I ended up putting in a 12AX7 which did.


I thought I would get my gear in order while I'm down, but everything is going kaput and Im afraid to touch it.

 

[Yelly]

FWIW I replaced the EV in my Mesa Boogie Mark iii with a Jensen Neo 100 (not the Tornado) to get the weight down and it has become my favourite sounding speaker. A lucky sonic find as I bought it so I could lift the amp off the ground like I could years ago when I bought it. I swear blind someone has fitted a neutron star in it somewhere. These speakers are very shallow too. None of the brittleness of the first generation neo speakers.

 

[Wally]

Big Al, I wish I were closer....I would do you a favor. Until one knows what went up in smoke, it is difficult to give any advice on what else to do. It could be minor smoke, or it could be major smoke. Can you pull the back panel and show us a picture or two???
Those leather handles can last a while....as long as people do use them to lean the amp forward to look at things, right? Cap upgrade?? When was this amp built?

 

[CoyotesGator]

Dang it Al!

It is great to hear you're playing some.

But now you've turned to attempted amp murder?

Like Wally said, if you post some pictures of the carcass I bet we can point you in the right direction.

 

[TM1]

Al; Probably easy enough.. a couple of questions.. How old are the filter caps? How old are the 6L6's could either he a bad dropping resistor between a one filter cap to another or one of 470 ohm's across a 6L6. Fender's aren't hard to work on from this era.

 

[Big Al]

Thanks fellas! I can't really play, I just plonk away in the part of the neck I can grab. I'm an amp serial killer though. I ain't touching a tube amp for awhile.

Try to get Nick to post pics. I have a very good tech so when I have the dough I'll get them done.

 

[J T]

Uh oh sounds like power handling. Something is drawing too much power.

Could be OP tube, Bias frying power tubes, Bad cap, Bad transformer.

 

[Wally]

IT could be any one or two of numerous things....you hope for a resistor that went south, right...maybe due to a bad tube.
IT could be a cap. Hopefully the trannies are not affected.

 

[Big Al]

I don't think the Super is serious. It still made guitar sounds at power. Sounded a bit odd and the presence knob had no effect. It is a clone, Mojo?, transformer seems OK. Had shitty tubes I replaced. NOS Sylvaina 5881s and 12AY7's normal phase inverter 12AX7?

It did make some loud cracks and pops so I shut down and noticed the smoke. I figure I'll take it in and have the obvious done, not sure of what it has but I will have the electrolytics and filter caps replaced with best quality new.

Are there better values or is stock good enough? I know I like higher than stock filter values on my BF Fenders. As long as it is on bench are there things I might have done to improve function and reliablity and maintaining classic woody reedy tweed Super tone?

Would it make sense to take the chassis out and send it to a Specialist and can you recommend some? Guitar playing tweed fanatics who get it?

I'm not a skinflint, I budget my income so I don't get in trouble. Not gigging, still in physical therapy and may never really play again, though I haven't given up. What I mean is I can pay for repairs but in a couple of months would be better and easier for me to shp, etc. I don't want anybody not recommending someone because I'm a payment risk, I'm golden in that respect.

 

[thejaf]

If I had to guess based on your description, sounds like a filter cap went bad. When going bad, they often let out the dielectric oil and that starts to smolder and smoke when contained within the Fender style cap cover. Increased pops and crackles happen because one stage of filtering just vanished, but amp still making sound because loss of that one filter won't kill signal. I'd have all filter caps replaced, since loss of one could indicate stress to the remaining. I like F&T caps, had great luck with them - absolutely quiet and dependable.

 

[B Ingram]

If I had to guess based on your description, sounds like ...

I'd warn against speculating based on what's been said so far. There's many ways an amp failure might result in smoke.

There's no reasonable way to guess without at least a picture inside the chassis, to see if it's obvious where the smoke came from. At that point, you could come up with theories about why the part smoked, and test out those theories to find the real problem (and the fix for that problem).

At this point I'm hoping for Al that it was only a resistor that let out the smoke, because it implies the fix will be cheaper than other possibilities.

 

[becks bolero]

https://www.youtube.com/watch?v=Leua_V-g4fk

 

[Wally]

+1 with BIngram.....there is too little info at this point to be definitive.

 

[Big Al]

+1 with BIngram.....there is too little info at this point to be definitive.

Yep, I didn't expect a diagnoses, I was looking for advise on anything I should be aware of with regards to this models circuitry. As I will be sending it to somebody to fix, I'd end up killing myself if I tried. If any of you guys had some good nuggets like recommendations for particular part values or tricks to improve stability or tone. Stuff different from the stock schematic. My tech only repairs stuff exactly like the stock amps schematic, and if I want something different I have to specifically ask, he does not mod amps, hates the idea of it.

I have heard so many different things, and I am not knowledgeable enough to know what any of it really means. Someone told me about improving my BF Fenders output filtering and it has resulted in quieter performance and maybe a tiny bit of tightening up on the bass frequency response. Someone I didn't quite trust enough to believe tried to tell me about changing all the values in the tone stack, but I LIKE FENDER TONE and I want my Tweeds to sound like Tweeds. Tighter less mushy bass and that open mid/woody/reedy/growly thing that tweeds do.

I will try and post pics and hey, Wally, or B Ingrahm any of you guys want a crack at it, I'd be happy to ship in a couple months come Spring, or if you want to tackle it now, I could ship the chassis, pay a deposit and pay YOUR REGULAR CHARGE. People have to make money and I like to pay people what they are worth.

Or if you know someone you can recommend that would be cool too.

I am just an idiot about this stuff. I can do just about anything to fix a guitar, I've built them, but other than knowing how to use an amp well, the rest is a great mystery to me and you guys are like the Professor on Gilligans Island.

If not, ANY advise would be most welcome.

 

[Wally]

Big Al, unless a player had specific concerns or complaints about what the amp does, that circuit is good to go imho and ime. There are ways to tighten up the low end just a bit if the player wanted that. IF it were a vintage tweed perhaps I would advise against modding, but it is a clone. I feel like what a player wants, a player should get.
As far as reliability, the circuit is not a problem. WE don't know with what component that amp was built, though.

 

[Big Al]

Thanks, Wally. That reinforces my natural tendency to stick to stock circuits. I'll have my guy blueprint and upgrade to quality components.

 

[B Ingram]

... I was looking for advise on anything I should be aware of with regards to this models circuitry. ....

... I'll have my guy blueprint and upgrade to quality components.

Since it's a clone, it's probably not that old right (at least not 50-60 years old)? Any idea on the exact age (if you didn't have it made for you)?

Do the tubes fit tightly in the sockets, or is there a lot of rock & wiggle? I would be concerned if you said, "Yeah, the 6L6's barely stay in their socket; they tend to fall out when I move the amp." Or, "The sockets seemed tight enough, but I tried some JJ output tubes and now the sockets barely hold on to the tube."

I usually expect a resistor or transformer to be the source of visible smoke. So you'd be expecting to find one of those types of parts to have some visible burns (though a transformer's burns could be internal and not immediately visible). Once you know *what* burned, you figure out why.

The "Why" usually comes down to excess current. Too much current caused the part to get too hot, which created the burn & the smoke followed. The location within the circuit is the clue for possible ways the burned part could have passed too much current. From that you come up with every theory you can on what failure could cause the excessive current, then step through testing/excluding those theories.

My question about snug tube sockets aimed at ruling out a worst-case failure: If your output tube sockets were very loose, you could have intermittent contact with the tube pins. If firm contact was lost on pin 5, you'd hear crackle (due to intermittent input signal to the tube). And if all contact to pin 5 is lost you also lose bias voltage, tube current skyrockets, and you hope a fuse pops before your output transformer lets out the magic smoke (it's the magic smoke that makes your transformer work :laugh2: ).

The above is not the only way to cause smoke, or even a leading candidate. Shorted filter or bias caps could cause a resistor to burn (but more often these caps fail gradually by losing capacitance and result in hum rather than smoke). Leaking coupling caps could create a situation that would result in smoke, but the most likely candidate in that cause would be the caps between phase inverter and output tube. Faulty wiring (or wiring methods) could result in a short circuit and create smoke. So it's hard to venture any reasonable guess without a starting point.

That's why I asked for a picture of the inside of the chassis earlier. I figured it would give a visible clue for where to start on this thing. A tweed Super is not a "problem circuit" the way some folks talk about Vox amps or the like. Typically they can/do last 50 years or more with not much beyond tube changes & the occasional filter/bias cap replacement when the thing starts humming (and I've been assuming you have a late-50's 5F4 type circuit with fixed bias 6L6's). I've got a Super clone myself that I built maybe 20 years ago that hasn't required any maintenance.