Thunderverb 200 Channel switching issue

[lucantonio]

Hello everyone,
Im having a strange issue with my TH200. it seems to be permanently stuck on channel A. The switch does nothing, neither does the footswitch. Just Channel A all the time! I thought this might be a bad tube issue so i replaced all the pre amp tubes but was surprised to find it had not changed.
I opened the chassis and made sure that the switch was connected and everything seemed clean and in order.
Im a little stumped but a further development, my reverb has stopped working as well.

Has anyone ever come across this before? Thank you for any responses

[bclaire]

Not sure - the main issue people have is with defective guitar cables connecting the footswitch. Maybe the relay for switching - you have full power coming out of the wall, correct? If the voltage from the wall is below a certain voltage, it might not channel switch. Try the amp in a different location to be sure.

[lucantonio]

The amp is getting good power and im using reliable cables! The amp seems to be stuck on channel A, Even the channel switch on the front doesn't change it. Ive tried changing a variety of Pre amp tubes and the problem still remains. Its seemingly stuck on channel A. I took apart the amp and inspected the switch and board

https://www.dropbox.com/s/xq32kdzc0xvg8 ... M.jpg?dl=0" onclick="window.open(this.href);return false;

[Jondog]

It won't be a tube issue. Sounds like you need a tech to look at it, specifically the relays and relay power circuit. Could be a bad switch too. Make sure the footswitch cable is unplugged from the amp to test the amps channel switch.

[lucantonio]

So i tested the switch and footswitch, the switch had no effect on the channel but the footswitch worked with other functions such as the reverb and the attenuator..
So i looked along the pcb board and found the relay for the channels A-B. It uses a small omron gv5-1 IC that doesnt seem to be damaged in any visible way.
So my theory is that somehow the relay bit has broken in some way thats not visible.

Thank you all for the support so far!