[Boatanchors] "Magic" 5Y3?

[Richard Knoppow]

    FWIW, I have an RCA AR-88, been completely recaped. It uses a 
5Y3 rectifier and has a VR-150 regulator. The regulator begins to 
glow right away when AC is turned on. Evidently, the rectifier 
begins to conduct as soon as any voltage appears on the 
filaments, even before they glow. I don't think anything is wrong 
with the tube. As others have said the voltage in a supply with a 
capacitor input filter can go very high before there is load on 
it. While the voltage is there quickly the other tubes need to 
warm up a bit before the set draws full load so the supply 
voltage will be very high to begin with and then drop rather 
quickly as the rest of the set begins to draw power.

On 9/28/2021 11:38 AM, radio_man at wbsnet.org wrote:
> 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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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL