[Hallicrafters] Some HT-37 questions

[wb8jkr at juno.com]

> You can improve the odds of your transformer not failing by using 
> solid
> state rectifiers and unsoldering the filament leads at the rectifier 
> tube
> sockets.  This keeps any high voltage off of the rectifier windings. 

 A good point! I didn't consider that.

> You
> will probably want to put some resistance in series in the low 
> voltage solid
> state rectifier to keep the LV from increasing too much or you can 
> get a
> Weber Copper Top SS replacement for the 5V4 that already had the 
> series
> resistance built in it.  It's not necessary to use series resistance 
> with
> the HV as the 6146's will handle the increased voltage without any 
> problem.

  Although a slight increase in the bias may be in order, maybe
about 2 volts.

 Mark  WB8JKR
 
> There are people who will rewind your transformer if it is shorted, 
> not
> inexpensive, but certainly doable.
> 
> Watch out for stuck slugs in the RF coils.  I am fighting stuck 
> slugs in the
> 20/15 meter mixer and driver coils in one that I am rebuilding.
> 
> All electrolytics probably should be replaced without bothering to 
> test
> them.  They are old and more than likely tired.  There are not very 
> many
> paper capacitors in the HT-37 and it wouldn't hurt to replace them 
> too.
> 
> Good luck.
> 
> David C. Hallam
> KC2JD
> 
> -----Original Message-----
> From: hallicrafters-bounces at mailman.qth.net
> [mailto:hallicrafters-bounces at mailman.qth.net]On Behalf Of Philip 
> Atchley
> Sent: Saturday, November 13, 2004 5:03 PM
> To: hallicrafters at mailman.qth.net
> Subject: [Hallicrafters] Some HT-37 questions
> 
> Hi Y'all,
> 
> I have acquired a Hallicrafters HT-37 HF transmitter that is very 
> nice
> physically, electrical status unknown.  This will probably be a 
> "overhaul
> project" later this winter (when I finish the SX-101A and the 
> BC-1004
> presently on the bench, they both belong to friends). But I've 
> received some
> Emails about the HT-37 that have me a little concerned.
> 
> Apparently they are known for power transformer failures.  Quote, 
> "It's not
> a matter of IF they'll fail, just when they'll fail".
> 
> Taking this into consideration, I have some questions as I 
> deliberate the
> upcoming task of overhaul (I'd hate to put a lot of work into it and 
> find
> the transformer is already shot).
> 
> 1.  How can I determine if it's already failed?  Does it smell 
> "smoked" or
> show other indications (I know some failures can be invisible).
> 
> 2.  Would it be safe to pull both rectifier tubes out and test it 
> that way
> for failure, checking for tube filaments, Voltage on the plate 
> connections
> of the rectifiers etc?
> 
> 3.  Assuming the transformer is good, are there any things that I 
> can do to
> reduce/eliminate the chances of transformer failure.  Things like 
> putting a
> lamp in the case for a week or two to "cook it", solid state 
> rectifiers,
> fans, separate filament transformer to reduce load on the main 
> transformer
> etc?
> 
> 4.  Are there any other "issues" with this rig?
> 
> 5.  FINALLY, if the transformer IS already bad, and having a slim 
> wallet,
> would it be realistic to pursue fixing the transmitter up, or would 
> I be
> much better off "parting it out (It's really quite nice overall)?
> 
> 73 de Phil,  KO6BB
> http://users.mercednet.com/beaconeer/
> Merced, Central California, 37.3N  120.48W  CM97sh
> 
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