Hallicrafters SX-42


I have a couple of Hallicrafters - wikipedia   Hallicrafters SX-42, (antiqueradio.org) receivers.  One is more or less a parts radio, the other will be restored.  Serial number HA-89503 was purchased by my father (CGC), circa 1947 - 1948.  The earliest date in his ARRL log book is 17 Feb 1948.  He was never licensed as an amateur but for a time he enjoyed hunting the air waves for commercial and government stations across the globe.  I suppose such activities are the equivalent to modern day "web surfing".  Except that hunting SW and amateur radio stations requires quite a bit more thought, art and effort, at least if you want to be good at it.
 
This radio was purchased with funds earned from forest fire fighting on Sunapee Mnt. in NH in the fall of 1947.

An influential industrial designer Raymond Loewy (wikipedia) designed the front panel of the chassis.

The two radios I have are: There seems little doubt that Serial number HA-89503 was purchased by CGC circa late 1947 - early 1948. The evidence for this comes in several parts.  Most obvious is that the manual schematic, and layout matches this chassis.  This original manual must have come with the purchased radio during this time frame.  The earliest date in the accompanying ARRL log book is 17 Feb 1948, so the radio had to have been purchased prior to that date.  The radio was purchased with funds from forest fire fighting on Sunapee mountain in New Hampshire in October of 1947.  The fire started due to a lightening strike near White Ledge above Lake Solitude.  The HA-88960 chassis, even absent the modifications, clearly does not match the manual.

Serial number HA-89503 is the one that once upon a time, 10 to 15 years ago as of 2009, powered up and made noise on one of the bands.  The other chassis HA-88960 does not have a power cord, and if it did, it may not have been working anyway due to the modifications.   CGC claims "his" radio was the radio which was "modified" to run SSB, and also had a temporary phono preamp mod.

Origin of HA-88960

CGC advertised in QST for a second radio in order to try and repair the first.  A Colonel, in the USAF, from NH showed up in the front yard of our house on Merriam St. in Lexington MA, hawking the HA-88960 chassis. This was soon after the move to Merriam Street, which puts the purchase in the 1972 to 1974 time frame.  Dad had advertised for another SX-42, presumably as a donor for the original.

The original SX-42 (HA-89503) may not have been working, it may have been on the shelves in the basement at Merriam street early on in 1972 - 1974, waiting for service.  At the time I had yet to be bitten by the radio bug, although I was interested in the discipline.


Modifications to HA-89503

Given the clear association of the manual and HA-89503 there seems little doubt that this relatively unmodified chassis is the original CGC purchase.  Furthermore HA-88960 clearly does not match the manual.  The 6SL7 "Audio Inverter" dual triode of the manual, and HA-89503, is not present in HA-88960.  In its place there is some other component.  It is not believed that this area of either radio had been modified by anyone.



There is an additional RCA jack that was mounted in the center of the nameplate on the back panel of HA-89503 but it appears to have not been wired to anything or is no longer wired to anything. This is no doubt the infamous "phono preamp port" that CGC decided would be a good thing for his audiophile interests. Young people do silly things. CGC claims this modification was done "shortly after purchasing the radio", which probably means he was not more than 20 years old when he thought it would be a good idea. I wish he had chosen a better location or not bothered to do it at all.


CGC claims serial number HA-89503 had a couple modifications.  One was the addition of a phono cartridge preamp.  This modification was done soon after purchase by CGC.  At the time the Pickering company had just released a new magnetic reluctance phonograph pickup with far better fidelity.  The problem was that it also required far more gain than other pickups.  The internal preamp of HA-89503 was the first attempt at making use of the new Pickering cartridge.  This did not have enough gain so an aftermarket preamp was purchased or copied, and  stuffed into the chassis.

A short time later the same preamp became available as a stand alone unit with its own power supply.  With this new arrangement, it was possible to remove the modifications to HA-89503, and return it to its normal configuration, except for the hole drilled into the chassis for the RCA jack.  The radio then remained in this configuration for some time.

The next shot is of the main deck HA-89503. There is quite a bit of dust, and oxidation. This is going to take some work. However, it isn't as bad as some of the pictures of "boat anchor" chassis you can find on the web.

CGC is unswerving in his assertion that an attempt to make the HA-89503 radio demodulate SSB was made by the son of one of the bosses at C&K components. "Kincade's son" supposedly did the work.  The radio was loaned to Kincade and his son, since none of CGC's children at the time seemed interested in radio or electronics.  Given the time frame (late 50's to early 70's), CGC's children were far too young.

At some stage of the operation, HA-89503 was brought back with a knob or two missing, and a couple front panel controls removed, although it is possible that those went missing later.  CGC claims the mod was attempted in the late 1950s maybe early 1960s.  Note that C&K Components appears to have been founded in 1957.  It isn't clear whether Kincade had a son of that age at the time.

The stipulation for the loan of HA-89503 was that it be returned in the condition in which it had been loaned.  With the exception of the front panel items, which may have been lost later, the radio seems to be as one would expect given its history.  It at least functioned at some level, after the loan period.  However, some function must have been lost, thus the attempt to acquire another unit to use as a parts radio.

Modifications to HA-88960

This chassis has been butchered.  After more discussions with CGC this ratio may have arrived in this condition.  The Colonel in the USAF, who was the previous owner, was the head of an electronic maintenance group.  It would seem plausible that this radio as well had been modified for SSB.  After WWII the amateur radio community started to pick up on SSB techniques.  Apparently SAC made SSB its standard form of radio communications in 1957.  Keeping these things in mind, it stands to reason that HA-88960 would also have been subjected to the SSB treatment.  However, in this case the person or persons responsible were not delicate about it.

Transformers have been removed or added, tubes, and capacitors added, and large holes cut in the main deck... butchered.

The modifications are placed in the circuit at or about the "AM. DET. & NOISE LIMITER" tube, a 6H6 type.  This is where you would think an SSB modification would be made.

Note also that an additional audio preamp would not be placed in this part of the circuit.  It would appear between the phono input jack (J1) and C106, the audio amplifier DC blocking capacitor.  Indeed, on this chassis, the RCA plug phono input jack has been removed.  Again, it seems unlikely that this chassis had been modified for high gain phono type applications.

Phono Preamp

This modification was made to the stock phono preamplifier circuit.  The need was for a pickering phono cartridge, which required more gain than the existing preamp could muster.

CGC claims this modification is notable by the inclusion of an extra tube, and a hole in the back of the chassis lid for a switch.  Since the modification was removed, the switch is now missing, and so may also be the additional tube.  It is also unclear which housing goes with which chassis, either chassis could have been placed in the housing with the switch hole in it.

On the older chassis (HA-88960) there are two additional tubes and a few additional capacitors but these are associated with the AM detector circuit SSB modification, which is an unlikely place for the insertion of a phono preamp.

It is possible that the CGC chassis (HA-89503) had been modified with the preamp.  However, given the modifications seen in HA-88960 it seems odd that HA-89503 escaped with so few scars, with respect to the SSB mods.  Thus it seems likely that the HA-89503, CGC's original chassis, escaped the SSB treatment.