[Hallicrafters] Precaution to FPM-300 Owners

[F. J. MacFarlane]

Today as I was rearranging my voluminous shack (a modified 5' by 5' closet that would be the envy of a WWII submarine sparks!) to accomodate my latest pride-and-joy (a beautiful HT-37 to go with my Drake 1A), a foul and fetid deed was done on my FPM-300 by a careless lout...yours truly.  The two spring steel locator catches had long ago broken off the 18-pin Jones cable receptacle for the 120 VAC cord, so when I plugged the receptacle into the connector on the rear of the FPM-300, I got it one row of contacts off.  I felt around and was satisfied that the receptacle was in correctly (oh, how I wish I had done a better job checking!), but when I plugged in the mains, a puff of smoke and the deed was done!  I destroyed Q101, Q102, V101, V102, and R122 (the heater currrent divider resistor for the 12BY7 driver) all in one swell foop.  It turns out both switching supply transistors are still available, and I have spares for V101 and V102, but it still frosts me that I did this.  TAKE HEED!  REPLACE THE LITTLE SPRING LOCATOR THINGS ON YOUR FPM-300 POWER SUPPLY CABLE CONNECTORS LEST YE END UP IN MY CONDITION!  I am planning on making up a pair of little aluminum locators to bolt on to the AC cable connector right now, and I'm going to do the same with my 12V DC cable connector soon.

BTW, I modified my FPM-300 long ago (1985) to accept any duodecal (12 pin Compactron) beam pentode amplifier (6KD6, 6LF6, 6MH6, 6LB6, 6LR6, etc.).  It involves recalculating the neutralizing fixed capacitance to allow proper neutralization, and adding a variable power resistor using a TO-220 Darlington transistor in the heater circuit (for 12 ops only...the noted bottles take more or less heater current than the original 6KD6).  I've used a GE 6LF6 in my rig for years (until I fried its heater just now!), and it took the abuse better than the original 6KD6.  If anyone's interested, I can send details.

Unhappily yours...
N5BGY

FPM-300
HT-37
KWM-2
Drake 1A
NC-57
Eldico R-104
Etc., Etc.


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