[Boatanchors] "Magic" 5Y3?

[radio_man at wbsnet.org]

Not sure if is "magic" or not but I have a Hammarlund HQ-129-X on my
service bench.  It is totally stock.  Uses a 5U4 rectifier.  When I  apply
power, the S meter pegs, B+ is there within a second.  Never  been
're-capped' or tubes changed in over 30 years that I know of.  Doesn't
seem to mind the instant B+.  Still plays great after warms up a minute or
two.

Rod
K0EQH







> Now- here's the mystery.  The Low-B+ buss is
> speced for 300V at 100 Mills, using a 5Y3 rectifier.
> But this buss is "getting froggy" on me.  When I
> power the supply, the Low-B+ buss, before the
> 5Y3 has had even a second or two to warm-up,
> immediately starts outputting about 460V.
> Watch this:
> https://photos.app.goo.gl/SFZo7t7RM6x2hqoKA
> I have not addressed the extra-high voltage yet.
> More concerned with how the thing is delivering
> "instant on" voltage.  Is the 5Y3 gassy, so it acts
> like an 0Z4?  Several tests show no evidence of gas.
> An open bleeder, so the micro-Amps sourced before
> the filaments heat is "spoofing" the meter?
> Nope; the bleeder is good.
> So this is interesting.  Anyone got any notions?
> I'll obviously be replacing the 450V caps I just
> installed with 600V, after which the FET regulator
> will make the Low-B+ buss "nice."
> GL OM ES 73 DE Dave AB5S
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