Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: stingray_65 on November 03, 2011, 03:16:45 pm

Title: bleed resistor calculation
Post by: stingray_65 on November 03, 2011, 03:16:45 pm

I want to add a bleed resistor to my B+ rail.

in my calculations do I just take into account the first filter cap?

or ALL the filter caps in the B+ rail?


My configuration is:

275-0-275 trans
full wave 5408's rectification (375v?)
2x 22uf 450v
dropping resistor
22uf 450v
dropping resistor
22uf 450v

I'm figuring a 500k 1/2w after the first paralleled 22uf's

should be about 1/4w dissipation and a decay to 20v of about 120 secs

right? That's figuring in all 88uf's in the rail

but if I only count the initial filters of 44uf then the discharge time is halved but the dissipation stays the same?? I think

I think I need someone to talk this out to me LOL.

Ray

Title: Re: bleed resistor calculation
Post by: sluckey on November 03, 2011, 03:31:36 pm

Don't calculate. Just put a 220K 1W across the first filter cap. That will take the entire B+ rail to zero in a reasonable time when switched off and won't put much load on the PT when it's on.

Title: Re: bleed resistor calculation
Post by: stingray_65 on November 03, 2011, 04:21:58 pm

DOH!

When I read your post I could hear PRR sayin keep it simple

220K 1 w it is

Thanks Steve