[Hallicrafters] HT-37 initial test

[Al Parker]

Hi agn,
	One other thing to do, it can be a "gotcha".  Do replace the selenium 
rectifier in the bias supply.  It will fail, if it hasn't yet.  When it 
does, the final tubes will draw way too much idling current at all times 
(maybe not if the switch is in "standby", I don't remember now).  If 
that happens the primary fuse will eventually blow, if it's sized 
properly.  You will have to add some series resistance with the new 
diode, I don't remember just how big, it's not in the notes on the 
referenced page, but I may have it in my notes somewhere, as I've done 
that in one not too long ago.  As a starting point, figure you'll have 
to drop about 30 v, at maybe 5 ma., so R=E/I  or R=30/0.005 = 1500 ohms.
73,

Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 3/22/2013 3:48 PM, Jim Marshall wrote:
> Bill, I have worked on HT-37's and 32's. In fact my primary station transmitter is an HT-32. They essentially have the same power supply in them. I would go ahead with the variac but with the stock rectifiers in it. This way you can be sure there are not any problems with it prior to solid stating the power supply. If there are problems, you can correct them prior to making the mods. I would definitely do the solid state mod, as it cuts down on heat by a huge amount, not to mention the higher B+ voltage.
> Jim Marshall, k6oly
>
>
> ________________________________
>   From: bill kipping <ke7kk at earthlink.net>
> To: hallicrafters at mailman.qth.net
> Sent: Friday, March 22, 2013 12:27 PM
> Subject: [Hallicrafters] HT-37 initial test
>
> Hello to the group, I have an HT-37 I bought 8 years ago from a honest fellow at a hamfest , said it worked well. Time to try it out. The power supply is unmodified an the transformer looks origanial. I plan to remove/isolate the 5V windings and replace the rectifier tubes with Weber Copper tops before bringing up on a variac. Anything else?  Tnx Bill KE7KK
> ______________________________________________________________