[Johnson] Valliant 1

[Damon Raphael]

You didn't mention whether or not your rig was working properly when you
decided to solid state the HV supply.

When I got my Valiant, the 866 filament supply on the low voltage XFMR was
shorted so I was forced to solid state it or find a new transformer.

I made 2 stacks of 1N-5408 diodes (1000 V PIV) and did the mod.  I used the
866 tube socket pins as tie points and removed the filament supply leads
from the socket and insulated the cutoff wire tips.  The rig came up fine
but the final plate voltage was about 760 volts (50 volts higher than
design).  I ran it that way for a while and then decided to lower the
voltage by putting 10 watt 50 ohm wirewound resistors in series bfore the
input to the choke filter circuit.  This had been suggested by a mod article
on the web. I never remeasured the voltage to see how much that had lowered
it because I fried my ohmeter tryin to do the measurement.

If you installed the diodes correctly and they were beefy enough to handle
the voltage and current of the circuit they shoulduld be OK.  The increased
voltage produced by the mod may have broken down one of the capacitors in
the output arm of the filter (C91 or C92) or some other component.

If the fillter capacitors are old, I would replace every electrolytic cap in
all the supplies to start.

You are having problems on the lower bands which suggest that you may have
one or more bad contacts on the wafer of the Auxiliary Coupling switch.
This can blow fuses. take a good look both sides of that wafer.  Clean it up
with De-Oxit.   Check the 2 mica capacitor networks which hang from the back
wafer of the band switch.  They are part of the PI network input.  If you
have loading problems because of a bad antenna coupling switch or bad
loading capacitors - some of those micas will fail dramatically blowing
sparks and flames from their sides.

Hope these suggestions are helpful to you.

73 and gud luck,

Damon, W7MD
Tucson, AZ


----- Original Message -----
From: <ATanner283@aol.com>
To: <amradio@mailman.qth.net>
Cc: <johnson@mailman.qth.net>
Sent: Monday, May 27, 2002 10:05 AM
Subject: [Johnson] Valliant 1


> I am currently working on a Valliant 1 I am trying to get on the air.
There
> was a discussion (I'm pretty sure it was one of these reflectors) about
using
> solid state devices for replacement of the 866 regulators. They are very
> pretty and all that, but really unreliable. I already had one short and
had a
> big arc under the chassis before the fuse popped. Please some info on
doing
> this. I had a problem also in that the dim past some one recapped this rig
> with higher than print specs caps. Called for 15ufd and they put in 22ufd.
I
> believe this makes the pwr supply work harder. They also grounded one end
of
> the caps, and grounded the center tap of the HF xfrmr. It appears when you
> measure this leg it IS ground, however the .202 ohm resistance for the
plate
> meter is in there. REALLY hard to read. Any how that made the plate and
mod
> meter inop. Fixed that up(have to order caps) but now cant get the plate
to
> dip on 40 and lower. Also have too much plate current for drive. Have
> replaced finals and neutralized them. This helped too. Any thoughts on the
se
> problems??? Thanks....(rig puts out RF by the
way...plenty).........Al/W8FAX
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