Fender Super Champ XD

[plaush]

Seasons Greetings everyone, hope everyone's holidays are going well. I'm gettin ready to dig into this SXCD which does not change channels (stuck on channel 2). First though, if I'm not mistaken I can set bias on the SCXD without the tubes in amp. Perhaps not. I am aware that I must have a speaker connected. I'm still learning and the memory gets foggy once n a while. Even though I am not using specific tube amp verbage to word my question, I am not without electronic experience. It's only in recent years that I have taken up tube amps. It was here on the forum that I found help refurbishing a vintage Fender Bandmaster. That project went well.
Anyhoo, on to the next project. Speaking in generalities... does anyone have experience or a suggestion as to what specific voltages/points to check for this issue. I have already checked solder joints for cables etc. I did notice some cold solder joints on a small chip. As it turned out I ended up replacing U1. Nothing changed. U1 is where I intend to start checking test points this time around. FYI, the amp works fine on channel 2.

[plaush]

OK I found my answer to the question about tubes being in. Uh... duh. Seems silly but somewhere along the line I remember working on an amp where I did some form of set up with the tubes out.

[Jazz P Bass]

Service Manual attached.

[plaush]

Thanks Jazz P Bass. I started at test point one and proceeded to test point 13. All of the voltages where looking good except when I got to test points 10 and 11. With the channel button up then down at TP10 I got 2.03VDC and 2.58VDC respectively. At TP11 the readings: 2.98VDC then 3.57VDC. According to the schematic these voltages would be appear to indicate that the channel switch is stuck on channel 2. The switch physically does what a good switch would do, clicks in stays in etc. I think I did some continuity tests earlier the led me to believe the switch was okay. At some point I suppose desoldering the switch and testing it may yield the fix . In the meantime, if anyone would like to explain the electronic (diode?) switching I would be interested in having a better understanding and grateful for the lesson. Isn't that why a specific pedal has to be used?