Front Load VT-40 sound problem ( stanby white rocker switch?) ( over heating?)

[jesse]

Hi I have a front load VT-40 with which I have a persistent problem that goes like this : after, generaly, a short while the sound shuts off and I need to press the standby off and on to get it back ( which will be usually instantly ) and it will hold another little while and shot off again... any ideas regarding this problem. Thanks in advance. Cheers.

[mozwell]

Jesse
Does your amp do this if you just turn it on & leave it, or only when you are playing.
When it shuts off, does banging on the amp with your hand fix it.
How old are the tubes in the amp.

Are you confident of taking voltage readings inside your amp, remember, there is high voltage in there & it can kill you if you dont know what you are doing.

First thing i would do (and i'm no expert) woudl be to look inside for burnt or overheated components, and solder joints that look "odd".
Also, if it has never had its power supply electrolytic capacitors changed, it may be worthwhile changing them.

Measure power supply voltages when you turn on, and then after the problem has happened.

Also, it looks from the schematic that is has a polarity switch & death cap, these should be removed & a 3 pin mains lead fitted.

Also, never turn the amp on without a speaker load connected.

[jesse]

The follow-up

Hello and thanks for the prompt reply... Actually I haven't plug it for a while and this is what it does... When I turn it on it plays fine, and then if when I leave the guitar iddle and the amp on when I go back to playing the sound really lowers in volume until I do strum my strings then it gets back to the proper volume... but it makes some " farting noises" and it's kind of noisy? Thanks in advance for your input... i'd rather have an idea of what the problem could be before I run to a technician cheers

[g1]

Try wiggling the preamp tubes around in their sockets and see if it makes a difference. Oxidized/dirty tube sockets are fairly common with these amps. If that doesn't help, the sockets may need to be resoldered to the circuit board, which is also common with these.

[Gtr_tech]

Cracked solder for sure.