[Hallicrafters] My first post

[Mark Bell]

Hi Bob --

Welcome to the list !!

----- Original Message -----
From: "Robert Stachurski" <WB4RFF at worldnet.att.net>
To: <hallicrafters at mailman.qth.net>
Sent: Thursday, February 27, 2003 12:52 AM
Subject: [Hallicrafters] My first post


> 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.

It's much better to use a variac to bring up an unknown piece of equipment.
Also, check the electrolytics first, especially in the power supply.
Replace the bad ones.

> 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.

Using the zeners may give you the correct voltage, but it will not solve the
problem of why the high voltages are there in the first place.   You'll
still have a problem, that may come back to haunt you later.   Find the
source of the problem.   Check resistor values in the bias circuit.  Did you
replace the electrolytics in the bias circuit when you replaced the selenium
rectifier?   If you didn't put in a dropping resistor when you replaced the
rectifier, you'll end up with a hight voltage,  but I don't know how much
more.  The last Hallicrafters I restored was my HT-32.  I didn't use a
dropping resistor when I replaced the selenium rectifier, but I was still
able to adjust the bias correctly.  As I recall, the bias circuits in the 32
and 37 are pretty similiar (if not the same) but I don't have my schematics
in front of me. Lots of things to check there Bob.

> Does anyone know or have information on the pwr xfmr secondary Voltages?