Howdy guys,
I hope you all had a great Xmas and all that jazz. Ive been doing a little research and I'd like to share.
I think the 170k resistor shown on the C+ modded Studio schematic is incorrect, the original MKIIC+ schematic is nearly unreadable and another version shows the resistor as being 1k. Also 170k is a non standard value which means its highly unlikely that it would be used. Here are the MKIIC+ schem's:
http://tubefreak.com/mk2c2.gifhttp://tubefreak.com/mk2c.gifThe schematic's of the Studio, Quad, Mk3, Mk4 and MKV (IIC+ Mode) all show a 270k value for that resistor, also the MK4's lead circuit schem is IDENTICAL to the C+ modded Studio schem with exception to the 170k resistor in question.
I have read that the MK4's lead circuit is meant to be the same as the MKIIC+ and based on the component values shown, this appears to be 100% true. This leads me to believe that the stock 270k resistor is the correct value and does not need to be changed. Compare the C+ modded Studio schem to the MK4 lead circuit:
http://genitalhercules.com/~mcrowe/img/lead_C+mod.jpghttp://tubefreak.com/mk4-2.gifHere is a link to the same Studio C+ Mod drawing that someone edited with some instructions, it might be helpful to anyone interested in doing the mod, but just ignore the 170k and keep the stock 270k:
http://voices.yahoo.com/converting-mesa-boogie-mark-iic-studio-preamp-3858698.html?cat=33#commentsmboogman wrote:
I'd be glad to help any I can. I haven't seen the insides of a quad before though. I can send you some pics of the inside of my Pre after the mods if you like.
Pics would be great thanks, maybe some close ups of the changed components? I have located all the parts to be changed on my Quad but just wanna make sure.
Cheers!
Shane