Marshall Valvestate Vs100 contour knob

[surface54]

Marshall Valvestate Vs100 contour knob stinky sound.
the contour knob is a B20K on the board.
does it make more of affect to change capacitors directly related to the contour knob or the pot outputs itself?

i love this amp, and when the treble is all the way up and the contour is all the way down man this thing is a powerful beast JCM800-esk. but i want a little more highs, but as soon as i move the contour knob even 5-7% this high scream comes out, and at 1-5% it doesnt make any sound change. ive tried to lower the treble and turn up the contour but then it starts to sound artificial. any way i could make the contour knob 1/10th of the power it already is, so id have to turn it all the way up to get to 10%?

im still new to this stuff but i understand that it can be done if thought out properly.

[fixr1984]

First off, welcome.
You could try lowering the cap on the treble control. That should let more of the highs thru. The schematic I'm looking at doesn't have the pots labeled but if VR11 is the treble pot then C60 (22n) could be lowered to 10n.

[surface54]

its VR12 actually, the last pot is treble. would it still be C60 in relation?

here is a pic

www.marshallforum.com/attachments/marshall-amps/1496d1257713885-1997-marshall-vs100-lights-works-tubes-not-lighting-up-1.jpg

[fixr1984]

It would be C61 (470pf) then. You could maybe try a 220pf. Also what VR# is the contour pot?

[surface54]

Nov 20, 2009 21:10:23 GMT -5 fixr1984 said:

It would be C61 (470pf) then. You could maybe try a 220pf. Also what VR# is the contour pot?

VR8 is contour

they go in this order
gain, contour, volume, bass, mid, treble

by the way do you know of good places to get these parts?
ive seen a couple sites online like mouser.

[fixr1984]

I will get you some links to a few sites. I need to examine the picture you linked to as well as the schematic some more. There are errors in the way the board as well as the schematic are labeled. I dont want to mislead you and give you wrong part values.

[surface54]

Nov 20, 2009 22:59:36 GMT -5 fixr1984 said:

I will get you some links to a few sites. I need to examine the picture you linked to as well as the schematic some more. There are errors in the way the board as well as the schematic are labeled. I dont want to mislead you and give you wrong part values.

[surface54]

www.marshallforum.com/attachments/marshall-amps/1498d1257714090-1997-marshall-vs100-lights-works-tubes-not-lighting-up-3.jpg

[fixr1984]

www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDisplay?langId=-1&krypto=6pWdQhy2AZPZ2sD8W5xEl6aJV6WqDHEGqOKNa%2FdOSS%2BvP0eGwqVHTrBN%2FQpczLQuRuf3csxuEIo%3D&ddkey=CookieLogon
www.smallbearelec.com/StoreFront.bok
www.pedalpartsplus.com/
www.effectsconnection.com/oscommerce


Mouser is a good one too but I find the site too confusing, too much inventory you loose track of what you are looking for.

[fixr1984]

C55 (22n) you could try lowering..maybe start with a 15n. That cap is controled by the contour knob. Hopefully lowering that will help make a diference.

[surface54]

Nov 24, 2009 21:17:33 GMT -5 fixr1984 said:

C55 (22n) you could try lowering..maybe start with a 15n. That cap is controled by the contour knob. Hopefully lowering that will help make a diference.

im good at doing the equipment work just havent learned the names.
what kinda of part would this be classified as?
a capacitor? and id look for 15n cap.

thanks in advance

[fixr1984]

Yes its a capacitor. Here is a chart I find very useful.
www.bobknarley.com/synth/capcodes.html