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Re: DIY 100W Bassman...again

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8/5/1999 4:26 AM

Re: DIY 100W Bassman...again

mm:

I was comparing your voltages to the those that I measured in the stock Pignose G40V (like a 5F6A but with an extra gain stage) as well as those on the Fender 5F6 schematic. It does seem like B+4 (V3/P6) is a bit high at 354vdc- the 5F6 is listed at 325vdc (+/- 20%!) and the Pignose was running at 290vdc (less headroom / more distortion). So what values did you measure for B+1(to plates) B+2(to screens) and B+3(to PI)?

You might want to add a 5th pole to the power supply and run V1 from that pole (maybe try a 10k/2W resistor with a 10uF/500v filter cap). I'd heard that you really shouldn't run 4 stages from the same power supply pole because you could run into coupling problems between the different stages. And you might also try replacing the 4k7 PS resistor with a 10k/2w to see how that effects the voltages to the three 12AX7's. If you wanted to lower the B+ voltages going to V1 and V2 even more then you might try replacing the stock 10k resistor with 12k or 15k.

Steve Ahola

Pignose G40V schematic (with the voltages I measured):

http://www.techaccessinc.com/blueguitar/g40_full.gif

8/6/1999 10:30 PM
mosrite man	Thanks, I'll ponder these possibilities and see what blows up first...Will keep you posted.

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