[Hallicrafters] SX25 power transformer question

[k0ewu at juno.com]

RE Variac-- Many rig power transformers  have been destroyed by the use
of the "variac" startup.
remember-- the dc output does not appear until the rectifier tube
filament/heater is up to temprature.
First thing to do is to verify the power transformer before it becomes
toast.
To do this you shall remove the rectifier tube. connect your AC voltmeter
to the 
hv center tap, the other lead to a plate pin of the rect socket. As you
bring the input voltage up the AC voltmeter shall read the same at both
plate pins of the rectifer tube socket. (sorry to be so long winded, used
to write specs for missle launches)
If everything is ok then you will get the same voltage on each plate
socket pin,
when your AC input to the rig matches the voltage input table for the
rig. This will be the line voltage as shown in your manual.
NOW you can run your Variac input test-but wait, we said that the
rectifier will not conduct till the filament gets hot-right? 
SO- the thing to do is to substitute a rectfier that does not depend on
filament temp to conduct. You want to find a solid state rectifier to
plug into the  rectifier socket- right? Then the DC out will follow the
AC input.ok?
to make these goodies contact the old man here and he will give you
specfics for your rectifier tube.

THOSE WHO KNOW WHAT WE ARE DISCUSSING SHALL NOT CUSS!
JACK        K0EWU at juno.com


On Mon, 2 Jan 2006 21:25:28 EST chandlerh2 at aol.com writes:
> Happy new year to all  .i just aquired a near mint SX25 100%untouched 
> and 
> very clean.  my 1st plan is to recap it .so i did the overall visual 
> check and 
> saw nothing wrong so i hooked it up to a variac. and slowly brought 
> it back up . 
> brought voltage up to 115 after a few hours and  evrthing was fine . 
> but when 
> i tried to get any stations radio sounded very weak and distorted so 
> i 
> decided to shut it down after i checked some voltages to get an idea 
> of what was 
> going on . nothing is hot and no odor from radio .  i cheked 
> voltages at the tube 
> sockets  and i have no plate voltage  and B+ is reading 377 at 
> rectifier tube 
> but only on 1 pin.[ it is supposed to 280,300 and 280] voltage is 
> only 5.5 
> volts at other 2 pins .  is my transformer toast or could something 
> else be the 
> culprit . thanks for any info 
> 
> steve
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