12000 series mainboard, anyone see any errors?

[charles]

I started the mainboard for my 12000 series earlier today and just finished up. Holy solder fumes batman that was a bit of work. I followed the mainboard layout on the CD, anybody see any errors? Thanks for looking.

Charles

[thousandshirts]

Looks good to me! I didn't spot any out of place values. Couldn't tell what the silver mica values were due to the camera angle, but they're all in the right locations. You may need to use a different bias resistor to get things into proper range, but I think that's about it, and that would simply depend on the tubes you happen to be using, anyhow.

[charles]

Looks good to me! I didn't spot any out of place values. Couldn't tell what the silver mica values were due to the camera angle, but they're all in the right locations. You may need to use a different bias resistor to get things into proper range, but I think that's about it, and that would simply depend on the tubes you happen to be using, anyhow.

Thanks! The Mica's are 500, 500, 47. I think I read some guys were using a 33k bias resistor, if I'm going to need to change it I'd rather do that now rather than later. I'll be using Eurotubes E34L's and my stock Marshall EL34's.

[thousandshirts]

Thanks! The Mica's are 500, 500, 47. I think I read some guys were using a 33k bias resistor, if I'm going to need to change it I'd rather do that now rather than later. I'll be using Eurotubes E34L's and my stock Marshall EL34's.

Well, 33k is a possibility, 47k is a possibility, 56k is a possibility. Can't easily say until the tubes are in, unfortunately!

[charles]

Thanks! The Mica's are 500, 500, 47. I think I read some guys were using a 33k bias resistor, if I'm going to need to change it I'd rather do that now rather than later. I'll be using Eurotubes E34L's and my stock Marshall EL34's.

Well, 33k is a possibility, 47k is a possibility, 56k is a possibility. Can't easily say until the tubes are in, unfortunately!

You have me thinking about adding a second bias pot. Speaking of bias pots, in a fit of manly overkill I welded the bias pot onto 4 turets! (makes with the body builder arm flex pose)

[thousandshirts]

Yes, that bias pot looks to be quite sturdy.

One of my favorite internet sites is John Chambers site. This guy has a (16) x KT88 build (1000w)...

Anyways, here's a web page on one of his restoration jobs on an older amp:

http://www.chambonino.com/work/vampower/vamp1.html" onclick="window.open(this.href);return false;

This amp has individual bias pots for each tube. This is an older amp, but this kind of control is perhaps even more useful today. When buying (very expensive) NOS power tubes one can be less selective and get away with some wide matches without too much hassle. Very cool stuff.