Marshall Mode Four channel problems

[joeymofo]

Hi,
I recently plugged in my Mode Four after not using it for a few weeks to find that the lights for the Clean and Crunch are both on on channel 1, and I can only select both of them (both OD's on channel 2 are working, but again, the light stays on on channel 1).
If i plug in the footswitch and press to switch to either OD's on channel 2, it changes during the time the button on the footswitch is pressed down, but as soon as you let go it reverts back to Clean/Crunch. The lights on Clean and Crunch both stay on all the time even if i have selected either of the OD channels. The LED behind the Clean button is also slightly dimmer than the Crunch light, both on the head and the footswitch.

I've never had this problem before, and i've lost access to my clean channel!
I also have reason to think someone may have tampered with it, but there is no visible wear or anything indicating this... any ideas?

Thanks all,
Joey

[joeymofo]

One final note, when I hold down the Crunch button the light on the Clean button goes off, but alas it comes back on again after I let go.

[Enzo]

There should be a row of four small MPSA13 transistors for the switching. Each has a 4.7uf cap from its base. I'd be looking for one of them shorted. Also possible problem with a stuck gate on one of the 4011 CMOS logic ICs.

[joeymofo]

Thanks for the reply mate!

Is this kind of problem expected over time and from too many knocks, etc?

I am showing your reply to my electrician friend and he is gonna have a look at it.

Cheers again,
Joey