Date: Wed, 29 Feb 2012 16:03:45 +0200
From: "Alf Pousar" <alf.pousar@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
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