I did not say there would be a problem replacing the mercury rectifiers with
solid state ones.
In fact there would never be a need for a "step start" when using replacement
solid state rectifiers because the filter
would have an input choke. Mercury rectifiers can't handle high peak currents
like solid state ones. So you will find that
all the transmitters that use them have an input choke. No need to remove the
filament transformer, just as long as the
ss rectifier is connected to one side of the secondary. In that way you can
keep the transmitter or amplifier in its original
state not decreasing its value.
If you were replacing a 5U4 you could have substantially higher output
voltage, this is not much a problem in transmitters
but is in receivers. You will have to add a few hundred Ohms in series to
compensate for the expected forward drop in the
vacuum rectifier.
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Jim Thomson
[jim.thom@telus.net]
Sent: Monday, November 09, 2015 6:20 AM
To: amps@contesting.com
Subject: [Amps] Hallicrafters HT-41
Date: Sun, 8 Nov 2015 06:38:48 +0000
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
To: James Branch <jamesbrookesbranch@gmail.com>, "amps@contesting.com"
<amps@contesting.com>
Subject: Re: [Amps] Hallicrafters HT-41
There is very little difference between the forward drop of mercury
rectifiers and solid state ones. On the order of a few volts at best.
A mercury rectifier forward drop would be about 15 volts that is a string of a
little more than 20 silicon rectifiers. If the ss rectifiers replaced vacuum
rectifiers then there would be an issue.
73
Bill wa4lav
## why would there be an issue using SS rectifiers to replace a 866 , 816 or
even a 5u4g ?? There is no issue, its been done for decades now. Just use
the correct number of diodes
in series, that’s it. Flip side to all this is.... the oem fil xfmr for the
866 would have to be tossed. In the oem FWCT, the B+ comes off of the CT of
the fil xfmr. Depending on
how much uf used in the B+ supply, you might want to add step start, etc.
Jim VE7RF
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