[Hallicrafters] My first post

[Robert Stachurski]

Many years ago I received (adopted or inherited) a Hallicrafters HT-37 xmitter and SX-111 rcvr.  Today I am trying to repair/restore this fine old pair. The rcvr is very anemic and it will need a good clean-up and realignment, the xmitter is a WORK in progress and a bear to work on.  I gave the HT-37 a smoke test but there was no smoke, the only problem was the plates of the rectifiers and amplifiers glowing a bright red before the fuse blew.  I replaced the filter caps (available from Antique Electronic Supply), put in a new fuse and gave it another smoke test. this time only the amp tube plates were glowing and an open L13 rf choke was replaced.
I lit off the xmitter again and this time the only thing that glowed were the tube filiments and tuning it up I even got a little RF output on the 80M band.  tried to do a coarse alignment but there was no output from 40M to 10M but there was smoke and burning comming from the mixer/driver set of coils and caps located under those shields.  C-25, one of the 5-25 pfd trimmer caps was arching and causing a lot of heat on the mica board to which it was mounted.  I know, I know the tech and operating manual said that all of the trimmer caps and board has to be replaced because that is the way the replacement comes.  Surplus Sales of Nebraska has these trimmers available as replacement for Collins equipment ($6.00), or another of the same type not designated as a Collins replacement for($2.00).  The only easy part of doing this job and replacement is moving the band switch rod out of the way so that the coils and caps can be disconnected from the switch wafers and removed for the work to be done.  A big hint is to make sure you make a copius amount of notes on hardware and wire placement before any work commences.  The Hallicrafters Tech and operating manual is notorius for NOT having a parts layout and diagram the only thing it has is a schematic but that was a help.
I am now working on the bias supply because the voltage here measures between -62V and -89V  this is nowhere near the -49V that is required, it isn't even in the ballpark figure of + or - 3%.  For this project I am going to use a pair of zener diodes as regulators to clamp the bias voltage to a max of -51V.  If anyone has any other ideas ideas I would sure like to hear them.  By the way, I did change the selenium rect. and used a 3A  200V PIV silicon diode in its place.  I also replaced the 10K bias set pot because I was unsure if the old one was good, even with an ohm meter check.  Remember, all parts may be ok with a static check but fail when a voltage and load is applied.  Does anyone know or have information on the pwr xfmr secondary Voltages? this is another fact that is missing from the tech manual and schematic.
I hope to check into the net one of these days but I want to do it with a Hallicrafters Xmitter and rcvr.
73's    Bob

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