Super Champ XD problems

[DrBGood]

Love this amp ! But it started developping cracking sounds if palyed loud or with much bass. Just like a busted speaker would do. But it is not the speaker. I have an external 12" cab and it does the same with it. It is nor the pedals or cable s or guitars, I've swiched them around and the noise persists.

Tubes ? I moved them a bit to make sure they're weel seated. No result.

What could it be ?

 

[ScottMarlowe]

I'd suspect a cold solder joint or a failing resistor / cap somewhere affected by amplitude.

 

[jtcnj]

^^^^^ +1
I say start with the easy stuff to eliminate.
I would start by removing and re-seating each tube, when cool.
Next I would swap in a spare tube one spot at a time to help eliminate tube failure.
That said, preamp tubes are said to last a long time and power tubes considered expendable.

 

[DrBGood]

Thanks guys.
I am not going to zap myself by playing with tubes ? Of course I'll disconnect it before doing so ...

 

[67plexi]

Is The Power Transformer getting Hot ??? If not Fender amps built the last ten years I have seen solder joints so thin or missed no solder at all
that will cause an arc. A burned resistor will be easy to see.

 

[ScottMarlowe]

Changing tubes should be safe. Only a cracked / open glass could be dangerous due to the plates (the huge part you'd grab if there was no glass) being charged. As long as the tubes aren't broken and you don't touch anything but the glass you're quite safe.

 

[jtcnj]

I meant one at a time and letting them cool a few minutes in between, power off, unplugged from wall. Dont take a chance on being in a hurry. No body should be in a hurry to die.

And I'll defer to pro's like Plexi. just throwing in my $.02 to help narrow down or eliminate the obvious.
I like the obvious, I 'm pretty good at the obvious. But you do need to stop and look.

Every talk to a guy who kicked himself silly trying to start an older / smaller motorcycle only to find it was out of gas. That kind of thing. Ya I was that guy. Dont be that guy. But I learned to not be that guy.

 

[DrBGood]

Tubes are Fender and were replaced by the seller. I reseated them to no avail.
Preamp would be 12AX7 ?

 

[syscokid]

Every talk to a guy who kicked himself silly trying to start an older / smaller motorcycle only to find it was out of gas.

Been there...

 

[syscokid]

Preamp would be 12AX7 ?

Yes, and 2 6V6's.
A friend with a Blues Deville, had a similar problem. One of the 6L6 power tubes were cracked and the corresponding grid resistor was very toasty.

 

[jtcnj]

Yes 1 smaller 9 pin is preamp 12ax7 and 2 bigger 6v6 power tubes. Pulling them out and inserting them again will kind of scuff the pins and socket contacts together. Also, Sometimes the contacts in the sockets dont make good contact with the tube pins and need to be re-tensioned, or bent slightly with a small jewelers or eyeglass screwdriver.
I had a no contact on one of my pre-amp cathodes on my 5e3 build start up. Just cheap sockets.

If you have any spares or known good same type tubes in another amp swap one at a time. Dont mix up the power tubes if they were purchased as a matched pair. But, if one power tube is found bad you should replace both with a matched pair, unless you have a balance pot and can perform the current balancing.

 

[DrBGood]

I have a Spuer Champ X2 too. So I'll swap it's tubes for the XD and see.

 

[jtcnj]

HOpe it works out simple good luck.

 

[DrBGood]

Didn't work, problem persists with new tubes. I'm not proficient enough in circuits, to go play inside that box. So it's off to the tech.

 

[gball]

Preamp would be 12AX7 ?

No, the preamp is all SS. That 12AX7 is the phase inverter.

 

[jtcnj]

Didn't work, problem persists with new tubes. I'm not proficient enough in circuits, to go play inside that box. So it's off to the tech.

Was worth a try. Good luck.

 

[DrBGood]

Fingers crossed.

 

[DrBGood]

No, the preamp is all SS. That 12AX7 is the phase inverter.

Phase inverter doesn't tell me much, but I'll take your word for it.
I would have to take a Tube Amp 101 course one day.

 

[WavMixer]

... Every talk to a guy who kicked himself silly trying to start an older / smaller motorcycle only to find it was out of gas. That kind of thing. Ya I was that guy. Dont be that guy. But I learned to not be that guy.

I only have two words to say about this...
Electric starter

 

[gball]

Phase inverter doesn't tell me much, but I'll take your word for it.
I would have to take a Tube Amp 101 course one day.

It's basically between the preamp and power amp sections. It's necessary in a push-pull amp, as it takes the single input signal and divides it into two outputs (one for each tube), one in the original phase and one that's 180-degrees out of phase, each signal going to one of the output tubes. It's one of the most important parts of the whole circuit.