[AMRadio] Too much HV

Tue Oct 18 15:24:05 EDT 2011

I'm speaking in practical terms. Five or ten volts is inconsequential when your dealing with 1500 volts.

Darrell, WA5VGO

On Oct 18, 2011, at 2:14 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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