Crate GT1200H won't switch to Solo channel.

[Duncandod]

-15.25, both sides.

[Duncandod]

Negative 15.25.

[g1]

So in post #22, where you said the voltages were 14V, did you mean -14V ?

Better double check B and C voltages when in OD also.

[g1]

Unfortunately, the schematic doesn't seem to show the footswitch jack, or where J21 goes to.

[Enzo]

OK, fine, here:

[Duncandod]

Doublechecked data. A values are negative, but correct as to measurement. I had negative values in my notes... I think I've been staring at this thing too long :/ sorry for the wild goose chase. I fixed the table on #22.

[Duncandod]

Discovered that my internet device was removing the - symbol, assuming it was punctuation. Fixed Sorry again for the bad info.

[Duncandod]

Q22 or Q28?

[g1]

Possibly. Verify that the switch has continuity to D25, cathode to ground should read short/non-short when you toggle the OD switch.
If that is ok, check D25 then Q22.

[Duncandod]

D25 zener failed. Broke in half when i touched it with test probe. 3.3v/1N746ARL. I have 5.1V IN4733A... not sure if that would go? Solo channel circuit still closed in OD mode.

[g1]

Use a zener of the correct voltage.

Solo channel circuit still closed in OD mode.

Not sure what this means. I meant doing a resistance check with amp off, D25/R74 junction to ground, switching solo switch. Only one switch position should read short from that junction to ground.

[Duncandod]

I was saying that the amp Haas switched to solo channel when od is on now, since the zener fell apart. I'm guessing that the zener may have been the issue. I'm replacing it and Q22/Q28 as soon as the parts arrive. I'll keep you posted. Thanks for all the help and for putting up with my fumbling attempts. I learned a ton about schematics in the last week.

You guys are truly awesome!

[g1]

Sounds like that should solve it.
As far as the footswitch goes, is it the 3 button Crate switch? The cables are odd, one is 1/4 inch at both ends, the other is TRS at amp end to 2 1/4 inch at the other end, do you have those?

[Duncandod]

Interesting. The sockets are identical 1/4", same as the insert and input Jacks. Yes it's the factory pedal. I'm really hoping that the zener issue will solve the logic anomalies. A bad zener at that location would explain a lo, seems to me, but I'm still suspecting Q28 as well. I've ordered all ic types on the board, just to be sure.

[g1]

Does the 3 button footswitch have 3 jacks on it, or just 2 ?