Whats the consensus on wiring a .01uf cap, or an RC snubber, or a MOV, across
each diode in a FWB, FWD, FWCT..in a B+ supply?
I see that some will wire one cap across each entire leg. Some will use
fast, and ultra fast recovery diodes in 60 hz supplies....with or without
a cap, snubber, mov across each diode.
Ameritron uses a .01uf cap across each diode. I read about the use of an RC
snubber for the 1st time the other day. Thats a new one
for me. I can see a snubber working better than a cap alone. Commercial
rectifier assys all come with a single MOV across each diode.
Whats the actual...problem or issue?? If its noise spikes being generated,
when each diode shuts OFF, I would have thought they would not make it past the
HV filter caps.
Then there is the bypass cap at the base of the plate choke, and possibly
another bypass cap on the B+ to chassis... b4 the plate choke bypass cap.
Is this..noise, spikes etc, even measurable ? Can you hear it on a RX ? I
dont operate MM, nor FT-8 modes, which might just be affected. Does it
manifest itself as ripple on the B+ ? Or is this all just semantics?
Just about every manufacturer of fast and ultra fast recovery diodes says...
not to use em on 50 and 60 hz supplies, wasted effort.....only to be used for
switching supplies.
Im rebuilding 4 x drake L4PS supplies..and used 7 x 6A10 diodes in each of
the 2 x legs of the FW Doubler. No provisions for a .01uf cap across each
diode. However, I did find
25-30 x .01 uf @ 5 kv caps in my myriad of bin boxes. I could easily wire
one across each leg of the doubler..and perhaps another one between B+
output of doubler....and chassis... b4 it gets into the filter caps..and
another one on the B+ output..after HV filter caps. Then perhaps a .01 uf, 1 kv
disc ceramic between B- and chassis.
Drake used a .001uf bypass disc cap, right where the B+ enters the RF
deck....and a .001uf doorknob bypass cap at base of plate choke.
Im not impressed with the ripple, under load, on the B+. I can see it plane
as day on the rf monitor scope. Anything over 700 w.. and its there, like
almost 3%. Its 208 V P-P..when
sucking 800 ma key down cxr.
Installing 2 x harbach boards in each L4PS B+ supply. Bought a 100 x new
rubycom 330 uf caps... which all measure 285 uf. 8 per board. 71 uf in
total filter C.... vs 25 uf with oem setup.
Jim VE7RF
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