[Hallicrafters] Hst 37 mods

[Gary Pannell]

Jerry thanks for your reply. I DID PUT A TWO PIN AMPHENOS MIC CONNECTOR IN 
PLACE OF THE OLD SINGLE ONE.be prepared to file with a rat tail for abt 20 
miniutes This chassis is steel and very hard and thick.When you use a D104 
mic and you close the mic for the contacts to complete the connection 
internaly in the G stand of the mic it closes the contacts that actuate the 
PTT at the same time.  You could drill a hole in the mic base and install a 
switch to bypass the mics open contacts so as to complete the circuit and 
the audio would go to the vox amp and it would work fine. I choose not to do 
that,as it would detract from the original mic.  You could put a switch in 
the wire that you added to the cathode of the vox amp tube and that would 
break the circuit and when you choose to use vox, you would just close the 
ptt bar on the mic and slide the chrome locking bracket up a little to lock 
the mic in the talk mode. This also requires a switch of some kind to be 
placed on the tranny front panel. which I am not a fan of. Or you could find 
a way of adding the switch to another function so as to hide it from any 
casual observer. I like this methode. I just haven't decided where to put 
it. I may disconnect the switch on the cal control and use it to break the 
circuit. I think this switch is not needed anyway for the purpose of 
adjusting the carrier supression.Its far more accurate to use the S meter of 
your receiver to accomplish this,and much more sensitive anyway.Just key the 
radio and put your receiver in rcv mode via front panel switch and adjust 
these for minimum reading and allah you have the best adjustment possible, 
There is no danger to the meter as in the case you forget to switch the cal 
button off for transmitting. It will bang the pointer into the right side of 
the meter with enthusiam. I've seen novice opps due just this when learning 
to tune this rig.  As for as the modulator I've constructed many of them in 
the past.They are generaly very simple circuits to design. I do not have a 
schematic of the one you have but it should be very easy to trace out the 
wiring and draw one for it,I have done this many times and it is quick and 
easy methode of using unknown gear. It will expand your knowledge of 
circuitry also.I elected to install the resisters and diodes on the bottom 
of the tube sockets,This makes a convient place to tie the componets for 
mechanical stability. by removing the vaccum rectifier tubes you take a lot 
of heat away from this tranny. You also eliminate the possibility of the 
filament windings shorting the HV to the secondary or the direct short to 
ground inside the transformer. I chose to install a T/R relay just inside 
the back panel and use the 5 volt windings in series to a voltage doubler to 
operate the addional relay . I used a 24 vdc relay , you could use a 12 volt 
and only one diode and one electrolytic, say a 100uf at 25 vdc. this makes 
the tranny usable with a transceiver or a receiver for it is in series. no 
dangling Dow KEYU RELAY FOR THE WIRES TO break off or short out behind the 
equipt. there is an extra hole in the rear apron that can be filed out a bit 
to install a so 234 coax fitting. There are plenty of contacts on the vox 
relay that is hooked to the accessory plug. also I make a wire harness to 
key the amp that is hooked to this connecter. It is also wired to the 
receiver for the standby and the audio for the vox which you have to connect 
internally in the rcvr to the accessory plug .this make for a very neat 
installation. And you can hook the external speaker to the pins that you 
have the vox adio on . This makes this a plug and play radio. Hows that for 
a philabuster?  Gary  WA5FWC  any more Questions?----- Original 
Message -----