[Amps] Bleeders

[Jim Thomson]

Date: Wed, 29 Feb 2012 16:03:45 +0200
From: "Alf Pousar" <alf.pousar at surffi.net>
Subject: [Amps] Bleeders

Why not skip the bleeder entirely, and make a current discharge circuitry when the session is over. 

If the anode voltage is very high then stack some thyristors and fire them with opto couplers.

So when you hit the big switch it turns off all power to the power supply, except for the auxillary

circuit that keeps the draining alive and then shut off .

Not very complicated to do and you get rid of the bleeder heat.

Alf OH2QM

##  You folks are making a mountain out of a mole hill.  The previous comment about the bleeder  sucking 
30% of the total power  is absurd!   New wire-wounds are dirt cheap at Mouser..even the 225 W CCS  variety.
If using oil caps,  use a bleeder that sucks 20-50 watts CCS.  Use a  100- 225 watt WW.  Then it won’t run blazing hot. 
In fact, install a 2nd, identical value bleeder in parallel with the 1st one.  Then you have a redundant bleeder.   The chances
of both of opening up is zero.  Wire wound’s these days, made by the various makers, are well made. 

##  If it takes several minutes to bleed down, who cares.  It would take several minutes to get the cabinet screws all out anyway, by
which time the caps are down to a low level, or zero.   It’s all a moot point anyway, since all these amps have B+ safety interlocks on 
them.   IE: take out the screws, then remove the top lid, etc, and the interlock will short the B+ anyway.   There is NO way to zap yourself. 

##  On these C input supplies, you don’t  need to be sucking a ton of bleeder current.  When on TX,  the amp will then be sucking loads 
of idle current. That alone will aid in improving regulation a bit.  Your REAL no load B+  is the voltage you measure with the amp keyed, but
with no drive applied..and drawing normal ZSAC.   .  B+ levels on RX  are another moot point.  

later... Jim   VE7RF