Hi Chris!
-> I have A Marshall Valvestate 8100 that just recently started acting
-> up. When I play through the amp (signal through the effects loop and
-> the effects loop controll knob cranked all the way) the signal gets
-> saturated (like theres too much low end) and the volume increases
-> slightly. It seems to play fine for the first 5  minutes or so, but
-> after that, the signal starts to act up..I tried turning the effects
-> knob hard left, and it the amp seems to be ok when set like this..
-> I'm guessing that it's a chip thats gone bad, but not really sure..
-> Any suggestions?
 I've worked on many, many Marshalls over the years, but nothing
recently. You have an effects loop that you are running wide open, then
you are hitting the effects with everything it's got and the effect is
freaking out. How would you like me standing two inches from your ear
shouting my lungs out? Take pity on the first opamp in your effects!
First off, "full on" on any control is not ever really intended in real
life, a switch can do that just fine, thank you. Controls are designed
to be used somwhere inbetween and usually that is about midrange in any
properly designed control, so try using about 50-60% of the travel from
off (counterclockwise) to on (clockwise) or about 1 o'clock on most
rotary knobs. Now your effect which has been shouted at, and might have
been damaged from hitting it so hard for so long may be needed to be
adjusted, also to about half way up for a start.
The thing is... you want to give the effect all it wants for signal, but
not too much, so that it can also work without strain or overload,
giving you a much cleaner sound with less noise (if you want the
ability to be clean besides what most guitarists want to do to
purposely distort the sound still being possible through the overdrive
of the preamp of the Marshall, setting your total volume out with the
Master volume). "Marshall sound", distortion boxes, compression and all
of that other stuff should be allowed to do what they do in a faithful
reproduction system all the way to the speakers which are purposedly
tailored for guitar sound.
The success in using your effects needs to have the levels optimized
between the send and the input of the effects device, and the return
from the device needs to be similarly adjusted for ideal use.
Give this a try!
 Bonnie *:>
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