tempus fugit wrote:
Here's the schematic you were asking about John. This is the section from my
amp that is used for remote switching. The original design was to have the
'effects 1+2 footswitch' connected to a mechanical switch, but I wanted to
change that to transistor switching so that I could incorporate it into my
pedalboard.

Where is the LED you mentioned in your post to
sci,electronics.basics,

"Thanks for the reply John.
I'm switching 12v at the collector
with 5v at the base.
The 12v is coming through a 100K resistor
from the previous device, so the current
is pretty small.
I've found that using a standard (2N2222 type)
transistor doesn't quite switch things
all the way off
( there is an LED indicator
that still glows faintly)."

I am assuming that it is something you are adding at the
transistor switch replacement part. I also need to see the
schematic for all that, to understand what you are testing.

If you just wanted transistors to replace the mechanical
switches, they could easily be 2N7000 type mosfets or
something with even higher resistance, since they only
switch the 150 uA current through the 100k resistors in the
amp. The harder problem may be keeping the off state
leakage current well below something like 15 uA to let the
effect be all the way on. If the LED gets involved in this
current, it will easily interfere with such a high impedance
deal.