Topband: DX-100 adventure contiunued

[Charlie Cunningham]

Hi, Bill

I was also going to ask if you have a choke input filter -or if you could
change the PS filter configuration to choke input to help a bit with the HV.


Also, check your line voltage - especially at night when the load on the
electric grid drops. I've seen my 240 VAC  here get up well past 265 volts
at night! Use a trusted, well calibrated volt meter and take some voltage
readings at different  times of day to get a feel for what the line
regulation looks like!  Note that a 10 % increase in line voltage would
increase that HV from 825  VDC to over 900 VDC.  10 % high line is not
really unusual.  Finally, you can check with your local PUC - there are
regulatory limits to how much the AC line is permitted to vary - but I'd
start with the power provider first. Maybe they need to drop your
distribution feeder down a tap at the substation. Excessive voltage is hard
on lots of things around your house besides DX-100s! The utility can cme out
and put a recording voltmeter on your line for a while to see what's going
on, if you complain about excessive line voltage.

GL!
73,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Tom W8JI
Sent: Wednesday, January 08, 2014 1:03 PM
To: Bill Cromwell; 'topband'
Subject: Re: Topband: DX-100 adventure contiunued

> I had used four caps rated at 450 volts/100 uF. They were in two pairs 
> series parallel for 100 uF/900 volts. Some hams cautioned me against using

> so much capacitance. So I removed one pair of the caps and ended with 50 
> uF at 900 volts. The plate supply remained over 950 Volts until I keyed 
> the transmitter when it dropped below 900 volts as might be expected.

There is actually very little difference in HV PS voltage between tubes and 
solid state when the supply is choke input.

High vacuum rectifiers have about 10-40 volts anode-cathode potential, so 
there isn't much voltage to be gained.

Is this still choke input, and do you have adequate bleeder current?


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