Model 38-3 and another wonderful RF unit
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City: Ferdinand
State, Province, Country: Indiana
Working against the clock, I tried my best to complete a Model 38-3 on New Year's Eve. Unfortunately, the radio didn't cooperate - upon initial power-up, it would only work on the first SW band - no AM, no upper SW band.
So I set it aside, and returned to the set a couple days later.
Fortunately, I happened to have a 38-3 parts chassis in the "archives." I pulled its RF unit, disassembled it and went over it with a fine-toothed comb, so to speak. Everything that could be replaced, was replaced (resistors, paper AND mica capacitors, wires). I checked every coil and all had good continuity. I did find a high-resistance leakage to ground which turned out to be an interconnecting wire; it, too, was replaced.
(Yes, all paper caps and some resistors had been replaced in the original RF unit, but I admit I got in a hurry and didn't check the coils for continuity as I should have.)
I pulled the faulty RF unit from the client's 38-3 and installed the other one - upon initial power up, Pawn Vanity's voice started coming out of the set's speaker. Success! It works on all three bands. Now for an alignment, and to see if the magnetic tuning works. Still needs a new dial scale, new grille cloth, and repro decals. But at least the worst is behind me now on this one.
Although this RF unit is a bit easier to service than some others I've worked on, I still think David Grimes (the Philco engineer responsible for the 1937-38 "Unit Construction") should be brought back and forced to spend every day, for many, many years, rebuilding several of his not-so-wonderful inventions.
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Ron Ramirez
Ferdinand IN
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Joined: Oct 2005
City: Grand Blanc, Michigan
Almost everyone hates the 37-38 subchassis, it would appear that the 118 or 690 would be the absolute worst.
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Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Well, yes, the 37-116, 37-675 and 37-690 RF units, along with the identical 38-116 Code 121 RF unit, are the most complicated, certainly.
Some more good news out of all this: The IFs aligned right up - and the Magnetic Tuning works perfectly; best of any I have ever serviced. The RF alignment will wait until I get a new dial scale and install it.
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Ron Ramirez
Ferdinand IN
Posts: 225
Threads: 14
Joined: Oct 2005
City: Grand Blanc, Michigan
I let someone else do my 38-2 so I am wondering how much that guy cursed when he tore into it, I think the 38-2 would be just a touch more complicated than the 38-3.
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City: Evanston, IL
From the looks of it, the 1936 Model 680 will give you a "run for your money" as well. That I.F. expander unit and the bandswitch...yikes!
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Joined: Dec 2005
City: Philadelphia, PA
I happen to like the 37,38 sub-chassis models. I have a soft spot for the 37-650. I was 10 years old in 1963 and was going to a summer camp northwest of Philadelphia. The camp was originally a farm and the owner converted it to the camp. The barn was the lunchroom and library and for used for other uses too. In one of the rooms were some chairs and tables and a 37-650 that belonged to the owner of the camp. One day it stopped playing. I was learning about radio and had a 1950 RCA tube manual my uncle had given to me. I learned as much as I could about tubes. It turned out someone had swiped the 5Y4G from atop the power transformer. I still remember the camp owner giving money so I could go to a little Hifi shop near my house that sold me a new Raytheon 5Y4GT to get the set going again.
Another time, I didn't want to play baseball. I asked the owner if he had any other old radios and he came down from his attic with a Philco 80. He handed me a bag of tubes which were the ones for the model 80. Fortunately, there were only three different types and you couldn't put them in the wrong sockets. These were my first exposure to Philco.
Getting back to the sub chassis', the only one that gave me trouble was a 6 volt DC 37-624 which had intermittent double .05 caps in the RF stage. If you pushed on the cap physically, the set played fine. Otherwise the RF stage was almost dead. I like the 37 and 38 model year battery models.
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Fred - hmmm, your comments almost makes me want to restore either my 37-643B or my 38-643B (or both!). Both are all-wave, battery-operated tombstones with shadow meters; they are probably the best battery operated Philcos ever made. At present, though, they are both "shelf queens" along with my 32-volt Model 32B tombstone.
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Ron Ramirez
Ferdinand IN
Posts: 225
Threads: 14
Joined: Oct 2005
City: Grand Blanc, Michigan
Well I like the 37/38 model line and all the higher tube count models had the sub chassis. I have a 38-2 and 38-116 along with a 38-4 w/o sub-chassis. I guess it could be worse the 37 and 38's could be full of rubber wire and that would make a bad situation even worse.
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Joined: Dec 2005
City: Philadelphia, PA
Ron, you really should restore your 37-643 and 38-643 sets. I know the reputation class B audio has but the 1J6G's pack a wollop, putting out almost 2 watts, ( I recall Philco slightly biased them with -3 volts to prolong B battery life). I think they compete very well with a set with a single 42 or 6F6 tube. The only thing these sets lack is brightness in their dials due to the 2 volt pilot lamps. The 2 volt bulbs are low current and just don't put out much light. Other than that, the battery sets perform every bit as well as their AC counterparts.
I still use an old battery eliminator marketed 20 years ago by Play Things Of The Past.
From my job. I got a power supply that handles upwards to 42 volts at 5 amps. It's perfect for 6 volt or 32 volt farm sets. These can be found at Hamfests or online auctions reasonably.
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Joined: Oct 2005
City: Charleston, WV
Hi Ron,
I must agree, the Philco "Unit Construction" was/is certainly a problem for the serviceman. Of course many other radio makes also have their own particular difficulties.
Whenever I lift one of these RF subchassis, I think how much the Philco authorized repair shops must have cursed these back when they were new. In those days, a serviceman might have had to lift the RF unit to replace a single paper capacitor. And no assurance that the same radio might not come back sometime in the near future needing another cap in the RF unit replaced.
At least now, when restoring a Philco, we can be reasonably assured that once this subchassis is lifted and all new reliable modern caps installed underneath it, that it should not have to be done again for a great many years.
Poston
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