Anyone have a Marshall AVT100???

[belfastneill]

Hi All,

I've just picked up a Marshall AVT100 second hand.
It was going cheap and I thought I'd take the chance on it.

God, I really wanted to like it!!!!
but......

I was just wondering whether anyone has/had one (I've seen a few threads about schematics) and whether their "Bright button" actually does anything on the clean channel?
For all my listening I can't discern a change of tone from it.
I'm playing in the house so pretty low.... so what I'm trying to figure out is; is it just this amp (button or electronics knackered), is this just something that only works under certain circumstances (on the amp in general) and if its broken how easily fixed is it?

Any help or advice greatly appreciated.
cheers,
Neil

[Jazz P Bass]

Marshall AVT100 Bright Switch

I have attached the preamp schematic.
It appears that the Bright Switch is on the Clean Channel only.
Try the switch with your guitar tone set at 10 (full treble).

[belfastneill]

Thanks for the reply Jazz.

The button still doesn't seem to make any difference to the tone with the treble on full.
All the other controls work by the way, just the bright function that's questionable.
I can't imagine them putting on a button that does nothing, so I'll have to assume its buggered.

I guess the first point of faliure to check the button itself.

cheers,
N

[Jazz P Bass]

Marshall Bright Switch

Look at the schematic.
The SW6a either lets R48 be 1 meg ohms or it shorts it.
With the amplifier off, measure R48 while pressing & depressing the switch.
If you get no change you will have to verify whether or not the switch itself functions.
It that is o/k then you must verify that the contact points of the associated components themselves agree with the schematic.
Happy Hunting.