Ok, i'll take Mr Chips' advice on this one and leave the amp as it is I'm quite content with the sound it provides as it is.

So far no sign of the problem! Like i said before, if it doesn't come back within one week i'll consider it solved and post it here in the forums.

 

Hello!

Just wanted to say that everything still works ok after 1 week and a half!

I think (and hope) that the problem is solved for good, and would like to thank MrChips and everyone else who helped out!

 

Hello!

Just wanted to say that everything still works ok after 1 week and a half!

I think (and hope) that the problem is solved for good, and would like to thank MrChips and everyone else who helped out!

I had this same exact problem with my Vox V9310. The JK6 trick worked like a champ, now the amp is back to screaming again. What a great fix it was, so simple. Great help and thank you very much.

 

Hello everybody!

I've got a problem that i hope someone here may help me with. I have a 12 year old Vox amp, a hybrid solid state with a 12AX7 tube Vox Cambridge 30 Reverb which i have modded (i replaced the problematic optocoupling from a LT9914 to a VTC5L3 and i changed the original TDA2050 chip with a much better LM3875). The modding done about a year ago made the clean channel sound superb.

Lately, though, i've been having a problem. Sometimes, in the middle of my playing or right when i kick start the amp early in the morning, the reverb is gone! Couriosly, it always comes back when i press the "boost gain" button from channel 2, even when channel 2 isn't activated! (i usually only use channel one with reverb)

I tried changing the 12AX7 tube with a new one, checked the wires leading from the spring reverb to the board and even resoldered some the reverb related connectors from the back of the board (from the reverb knob and from where the reverb wires meet the board + plus any other solder that looked "dry").

I don't think it's a heating problem since the problem appears even when i start the amp fresh, i talked with an electronic engineer friend which suggested it might be some sort of circuit problem since the reverb is always restarted when i press the "boost gain" button from channel 2, even when channel 2 is not activated.

Does anyone have any idea what might be causing this or what i might do to fix it? I really love the reverb on this amp and i would be very sad to have to buy a new one, but i can't go on any gig knowing the reverb might shut down randomly.

If anyone can help, it would be much appreciated! My engineer friend said he would help me, but he doesn't know much about amps so any tips as to where he should look for problems would help a lot. Also, i have attached the service manual with the circuit schematics to anyone that might be interested.

Thank you very much!

The first thing you want to do is isolate the signal between the input and the output of the springs. When the reverb is dead, can you get any kind of buzz if you touch the OUtput connector of the springs? (Or, simpler, give the cabinet a good KICK and see if you get any boings). If not, you can certainly eliminate anything before the springs. Start there.