TW Xpress Problem

[loupy31]

+Hi All,
I built my TW Xpress clone, over a couple of years ago, have used it with great result, last year I was lucky enough to get a 60's LesPaul re-issue, the combination of the two is great.
I have , however, Got a problem, Last night while playing in the spare room, the amp started to let out some poping sounds.
there was always a single pop when I turn on the stanby swicth but that was it, now after about five or so minutes, the same pop is heard then several seconds later another and then another, they would get faster as time went on.
the tone and volume of the amp does not seem to be affected,
I am not sure where to start looking for the problem, it could be a cap, or a tube, I just dont know.

Can someone help me out in fault finding this prob.

Regards Peter

[marcoloco961]

Most of the problems I have had to troubleshoot where the symptoms were a popping sound, ended up being a intermittent contact. If your input jack is a shorting jack check it out, they can wear from the fatigue of plugging and un-plugging the guitar. If not, a chopstick test would be in order to try and locate the problem. Usually this kind of problem will show itself in a chopstick test. Hope this helps.

[loupy31]

thanks for the advice, the poping noise is heard both with a lead pluged in and also removed...........I do have a spare socket, i will replace it regardless

[Cliff Schecht]

There is a similar thread about this issue in the technical discussion forum. Ended up being a pin not making good contact in the rectifier circuit. To troubleshoot a problem like this I would fire on the amp and wait for it to start making this sound. Then I would pull each preamp tube one by one until the sound stopped (starting with V1). This will at least tell you at what stage this problem is happening.

[RevD]

I've had loose ground wires pop as well, my old juke 5e3 did this, had me baffled till I rotated the grounds and tightened the star washer/ground bolt all was well again. Made sense, after a while the vibrations get to things, of course this is a combo too. Just a thought.

[Reeltarded]

Turn the amp off in between pulling tubes though. lol

[Firestorm]

There is a similar thread about this issue in the technical discussion forum. Ended up being a pin not making good contact in the rectifier circuit. To troubleshoot a problem like this I would fire on the amp and wait for it to start making this sound. Then I would pull each preamp tube one by one until the sound stopped (starting with V1). This will at least tell you at what stage this problem is happening.

That was me, so I'll just add that while sequentially pulling tubes is a good starting point, it can mislead you. In my case, pulling preamp tubes made the noise go away, but only because the arcing in the rectifier tube was only audible through the gain of the preamps. Chopsticking is what found it eventually. In your case, since the noise starts after a few minutes and increases with time, it's likely to be somehow heat related (not overheating, just thermal expansion).

[RevD]

Another question, what type of sockets did you use? I had a 18 watter that did that, turned out it was a cheap socket in the pre-amp soon as I replaced it it was fine. Another thought, good luck with it!

Regards,

Don

[marcoloco961]

thanks for the advice, the poping noise is heard both with a lead pluged in and also removed...........I do have a spare socket, i will replace it regardless

If the amp makes the noise with or without a guitar plugged in I would doubt it was the input jack. One thing I forgot to mention is to turn out the lights and look in the chassis while she is making the noise. Usually noise like this stem from a failing contact, sometime a small spark is present with this kind of problem. I found a bad contact in a three prong plug on a power amp this way recently. Good luck, hope you find it.

[johnnyreece]

Had this happen on a JTM 45 clone. The cap board had a bad connection, and would periodically arc (making the popping sound). Yet another idea for you to try.