Time to get out the DVM and start looking for s/c parts ...
D2 would be right in the path...Start there ..

kip
wrote in message
ps.com...
Hi,

I've done a stupid thing with my new guitar amp, and sent 9v DC where
it shouldn't go, and now it won't change channels.

Please can someone help ? I've uploaded a schematic (866kb) he
http://homepage.ntlworld.com/anengineer/vc15.pdf

Scroll to the bottom page (page 3) (for some reason they included an
earlier, incomplete revision on page 2 !), and the relevant section is
grid ref A3 to A6.

I connected a badly wired external switch box to the 'Remote' jack in
grid A3, and sent 9v DC up all three connectors - sleeve, ring & tip.

The normal operation of the amp is that it has a 'clean' channel and a
'distortion' channel, switched by either the latching push-switch on
the amp ('SW2A' - grid A4), or by a remote switch via the jack in grid
A3. Either switch takes the line to ground to activate the relay (grid
A5/6), which switches the channel, and illuminates LED1 (grid A6).

Currently, LED1 is permanently ON and the amp is stuck on the
distortion channel. Neither SW2A nor an external switch has any effect
now, and there is no 'click' from the relay.

The 'Remote' jack also allows switching on/off of the built-in reverb
(short ring to sleeve [ground] for OFF) - but thankfully this seems to
still be working ok. - However, shorting tip and ring on the 'Remote'
jack also switches the reverb off - suggesting that the 'tip' line is
permanently shorted to ground.

Looking at the schematic, my guess is that D2 has gone short-circuit -
but then, that is an amateur's guess !

Please could someone suggest what I should test / replace ?

Many, many thanks to anyone who can advise.

Cheers,

Kev.