Traynor YCV40 Channel Switch Repair (What Happened?)

[garytoosweet]

What happened here?

Traynor YCV40. Problem was the Channel switch on faceplate does not work. Channel is still able to be switched by using a foot switch.

I looked at the schematic and saw that the switch is a DPDT that passes through the foot switch jack. I thought likely a bad switch or bad connection (probably a dirty FS jack). Since switching is still working with foot switch, everything downstream should be OK.

Switch tested 100%, all connections including through the jack tested 100%.

I began re-checking everything, getting the same results consistently.

I decide to manually ground out the foot switch pcb pads to see if it will switch without a FS plug inserted. I attach a probe to ground, and contact the FS jack PCB pads. I hear a relay click and the amp changes channels, I release the probe from the pad and the channel switches back. Hit the front panel switch and now it is working perfectly.

I can not get it to fail again.

The schematic is attached and the relevant portion is in the top right corner.

Any ideas what happened? It's now working but I didn't fix anything, want to understand what the problem is or may have been.

[garytoosweet]

Ok I will embarrassingly admit that I eventually was able to reproduce the error by chop sticking the foot switch pcb. It had a fickle intermittent connection that showed good every time I read it with the DMM, but I was able to make it open again by chop sticking.

Should have done a round of the old chop stick before busting out my meter...

[Enzo]

About those footswitch contacts... You need to measure resistance, not just continuity, and not just some low resistance. Those cutout contacts need to measure less than half an ohm. If it reads like 3 ohms, you are tempted to say "good enough" and move on, but the fact it is a few ohms instead of zero tells you the contacts are NOT pristine, and may be only 3 ohms now, but a little vibration later they might rise considerably, enough to affect operation.

Always measure.