Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Well, folks, back in the spring I said I would restore this 37-650 chassis that I had out in the garage. It was the best looking of the three 37-650 chassis which I owned. I planned to trade this chassis, once restored, for another radio.
The main part of the chassis went smoothly without any significant issues.
Then came the RF unit.
I was dismayed to find that it would work intermittently...and when it stopped working, a tiny bit of smoke would start to emit from one of the band switch wafer sections in the oscillator section of the RF unit.
Okay, a burned carbon track in the switch wafer. It had happened before to a 37-650 I had serviced, and I was able to remove the carbon track from that switch wafer and fill the resultant gap with epoxy, after which the radio worked fine.
Not this time. I could not find the carbon track!
So...I tried the oscillator section from the worst of the other two 37-650 chassis I had. The switch wafers were fine...but band 3 (the highest SW band) would not work! It produced only static noises but did not tune any stations.
Next, I removed the Band 3 oscillator coil from the oscillator section which was smoking in the switch wafer, and installed that coil in place of the Band 3 coil from the replaced oscillator section.
Result...same problem.
The odd thing is, both oscillator coils had good continuity. But I have learned from servicing 1937-38 Philcos in the past, that "good continuity" does not always equal "good coil."
So, in desperation, I pulled the entire RF unit from the 37-650 chassis I had planned to keep for myself.
You guessed it...that solved the problem and the set now works on all three bands.
Here are a couple photos of the now restored 37-650 chassis in action.
[Image: http://www.philcoradio.com/images/phorum...0001-1.jpg]
[Image: http://www.philcoradio.com/images/phorum...0002-1.jpg]
--
Ron Ramirez
Ferdinand IN
Posts: 292
Threads: 17
Joined: Aug 2010
City: Yorkville IL
 Nice !!
Glenn
Posts: 2,353
Threads: 92
Joined: May 2010
City: Clayton, NC
I feel your pain. I had an intermittant issue wiith my 38-665. Lost volume/reception. When I placed a screwdriver on the 6A8, cam in loud and clear. Hmmmmm, RF deck prob.
Turned out to be one of the very thin wires in the RF Unit portion of the RF deck was broken and making intermittant ctc. I repaired this, and since I had the d**n deck out of the radio I replaced the caps deep in the deck, which was somthing I had been putting off until the Radio Fairy blessed me.
Plays well now. Worth the effort, but those RF decks are a pain in the ____ (thing one sits on).
Posts: 7,212
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
Hey Tom
That sounds a bit like problem I've been having with that confounded 600. It's fairly intermittent but the volume will drop to about half and will get very noisy. The only thing that brings it out of this operation is to touch the plate pin of the 6A7 with a screwdriver. It will go pop and work fine for a week of so then back to it's old tricks.
It's a bit hard to troubleshoot because it seems that the mixer and IF/det don't behave well separately. The mixer needs the loading of the IF can and the regenerative det needs load from the secondary of the IF can.
I've double everything I can think of, pulled the IF transformer checked the windings, resolder all the connections, cleaned the ground connections and then ran ground wires to be sure, tried several 77's and 6A7's
I'm starting to think the tube socket may have some sort of high resistance path.
That's my stumper.
It's funny all of the other 4 toobers(80's,81's,84's,37-84's) I've worked on haven't been too much of a problem. Mostly the same old bad coils, caps,and resistors. Did have one with a bad IF transformer but was able to repair it.
Terry
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Oh, I forgot to mention...I think I set a new world's record for number of times removing and reinstalling an RF unit in a 1937 Philco while working on this 37-650. I removed and reinstalled the same RF unit...or a different RF unit...so many times that I literally lost count.
David Grimes should have been sentenced to a lifetime of being forced to service these things he invented. Philco's "Unit Construction" was definitely not designed with the repairman in mind...in my opinion.
--
Ron Ramirez
Ferdinand IN
Posts: 393
Threads: 40
Joined: Sep 2007
City: St Clair Shores, MI, USA
Ron Ramirez Wrote:Oh, I forgot to mention...I think I set a new world's record for number of times removing and reinstalling an RF unit in a 1937 Philco while working on this 37-650. I removed and reinstalled the same RF unit...or a different RF unit...so many times that I literally lost count.
David Grimes should have been sentenced to a lifetime of being forced to service these things he invented. Philco's "Unit Construction" was definitely not designed with the repairman in mind...in my opinion.
I feel your pain. My 37-630T would not track correctly in the BCB. I mean it was WAY off while spot on at the other end of the band. Maybe you recall me asking you about that? Anyhow long story short, after I replaced various components including the tuner, caps, resistors (that really had nothing to do with it), no change. For the life of me I never figured that out. But once I installed the RF deck from my downer set, it tracks perfectly. My head spins just thinking of that weekend 
-Brian
If you collect or are interested in antique telephones, please visit Classic Rotary Phones
http://www.classicrotaryphones.com/forum/index.php
Posts: 1,703
Threads: 55
Joined: Sep 2005
City: Evanston, IL
From an original Patent in my archive:
Ron's nemisis outlined on scan.
[Image: http://www.philcorepairbench.com/images/1937unit01.jpg]
Happy New Year!
Chuck
Posts: 1,393
Threads: 69
Joined: Oct 2007
City: Linn Creek, MO
I ran into a problem on a Philco 70 one time, that liked to drove me nuts. If I remember right, I had re caped the radio and rewound one of the coils. The radio was playing beautifully, I put it back in the cabinet, just to have it quit a couple of hours later. I removed the chassis again, before I could do anything to it, it started working again. I let it play on the bench for two or three days, so I put it back in the cabinet. You guessed it! Well, this went on for five or six times. Put the chassis in the cabinet, just to have it quit working anywhere from twenty minutes to two days later. Take it out and it would work without fail. The problem turned out to be one of the trimmers for one of the IF transformers. This is what I found. These trimmers are put together with a hollow brass rivet. The mounting bolt passes through the rivet and the ground is provided by the mounting bolt. Well, the back plate of the trimmer is made of steel and had rusted under the flange of the rivet, causing an intermittent connection. I mention this because, this could happen to any of the old Philcos and cause some strange problems.
Steve
M R Radios C M Tubes
Posts: 909
Threads: 117
Joined: Jun 2007
That David Grimes Pfhilco fellow hasn't ever been a popular guy at my shop either. He created a hornets nest with the mid RF deck that wasn't even necessary at all. A oldtimer radio tech that worked in a few repair shops back in the 1940s - 60s told me they used to refer customers with these type philco 37-6xx chassis electronics repairs to their competitors radio repair shop across town just to pi** them off! The shops he worked in back in those days made more money by servicing other brands that were lots more tech friendly to service in much less time, and they turned out more work and made more money in the long run by passing on these particular models. He worked at several authorized Philco service shops. So therefore, David Grimes didn't do the Philco dealers/ techs any favors at all with his designs. He designed a chassis that the dealers that didn't care to service either! The Philco cabinets of that era sure are attractive though.
Posts: 4,611
Threads: 51
Joined: Sep 2008
City: Sandwick, BC, CA
I wonder why these Philco sub chassis have so much trouble? It can't be just the fact that it's an RF sub chassis, there were RCA and Northern Electric/American Bosch sets that used similar things and I've never heard a complaint about the RCA sets. On thing that I have noticed about Philcos is they seem to have a lot of front end problems regardless of the chassis layout. Maybe they cheapened out on components where they shouldn't have? I know that in one set I have from the 1940s they used brass plated steel in the IF trimmer screws rather then brass, and that sets like the Philco 60s have corroded coil problems thanks to the plastic insulation they used. David Grimes manufactured sets under his own name back in the 1920s and they weren't particularly anything to write home about.
Regards
Arran
Posts: 2,353
Threads: 92
Joined: May 2010
City: Clayton, NC
The RCA sets with RF decks that I have worked on had the components arranged in a manner that was easier to work on!
Terry: WOW, that is a tough one. When faced with problems like that I have found that measuring both continuity/resistance/short to ground for all the connections/components was what I had to resort to to find the problem. A Crosley 157 had a lead in the oscillator circuitry that was shorted,it went from the transformer to the tuning cap through the chassis. The reading it gave made it look like the transformer was shorted, but disconnecting both leads and re-measuring showed the transformer to have resistance. The 157 is a 10 tube cathedral with a chassis that is no larger than a 6 tube Philco, so the components are pretty crowded!
Steve: that is some good information! I will add your observations to my "bag of tricks."
Posts: 2,353
Threads: 92
Joined: May 2010
City: Clayton, NC
Oh yes, and Ron: your pain has one good result, in that your Phollowers will endure less pain if/when they work on a 37-650!!
Users browsing this thread: 1 Guest(s)
|
