[Boatanchors] "Magic" 5Y3?

[JAMES D COMSTOCK]

I would pull the rectifier tube and see if you still have B+. I have seen several radios that have had solid state rectifiers soldered to the tube socket under the chassis. Jim


> On 09/28/2021 12:54 PM Richard Knoppow <1oldlens1 at ix.netcom.com> wrote:
> 
>  
> 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
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