[AMRadio] Too much HV

[Dennis Gilliam]

Maybe the confusion stems from replacing a vacuum rectifier with SS diodes.
 Those tubes did have an appreciable E drop under load, unlike gaseous ones.

73DG

On Tue, Oct 18, 2011 at 12:14 PM, Mel Farrer <farrerfolks at yahoo.com> wrote:

> Well, Darrell, almost correct.  The 866A rectifier has a peak tube voltage
> drop (Approx.) of 15 Volts according to the old RCA tube handbook.  So you
> might see 20 to 30 VDC more with SS rectifiers, but I doubt it.  Hi.
>
> Mel, K6KBE
>
>
>
> ________________________________
> From: Darrell Brooks <hbrnut at suddenlink.net>
> To: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net
> >
> Sent: Tuesday, October 18, 2011 12:03 PM
> Subject: Re: [AMRadio] Too much HV
>
> Changing from MV rectifiers to SS rectifiers will not change the DC
> voltage.
>
> 73,
> Darrell, WA5VGO
>
>
>
>
> On Oct 18, 2011, at 12:52 PM, CL in NC <mjcal77 at yahoo.com> wrote:
>
> > Well, anytime I ever replaced a tube rect. with a diode, I always ended
> up with a higher B+.  The HA 10 I am working on does not have the choke in
> it.  It arrived with a 1900VCT xfmr, a bridge rect. and  a cap string
> totaling 16uf.  Unloaded, the plate volts rests at 2300, to much for idling
> 811's.  I removed the bridge rect. used only half the diodes in full wave
> configuration and get 1700 no load, which is OK.  I picked up an original
> Heath 3kv CT to put in it.  But in conjunction with Bill, who has the an
> original HA10 with correct PS plate xfmr, swinging choke, and oil caps, gets
> 2500 with a W2AU diode block.  I expect to end up with the same problem if I
> switch out the xfmr,  So I'm looking to solve Bill's HV problem and avoid
> creating a similar one.  I am putting inrush protection in it since the
> original HA10 plate xfmr was a known weak point, along with an internal
> ant/amp bypass relay.  Guess the choke will not make a return since
>  it is
> > obscenely expensive when newly manf., so upping the filter to a string of
> 6  450uf at 450vdc.  While the amp is not needed for use with the Heath
> Apache, it does come in handy with the C Line when running it on AM.  One
> fellow questioned the xfmr, both xfmrs have the proper 3kv AC out of the
> secondary, with 1500 each side of CT, no imbalance, so does not appear to be
> a xfmr issue.
> >
> > Charlie in NC
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