When you said it had shortwave, I figured it was just the old police band - but this set has HF clear up to 17.8 Mz. I had no idea that car radios were made with such coverage.
Two IF stages, an RF stage, a pair of 6V6s in push-pull, and a dynamic speaker! Were does the DC come from for the speaker's field coil? Usually, in AC sets, the field coil doubles as a choke in the power supply - but maybe this one comes straight off the 6-V battery circuit? I'm wondering if this chassis was adapted from a big, hunky ac-powered radio design? Do you have a car to put the radio in?
Regarding the B+ voltage disparity. If there is any kind of weird waveforms riding on top of the rectifier output, a DMM will behave strangely - even one labeled true RMS. I have a Fluke 179, supposedly true RMS, but it is not - unless the hash is symmetric about the zero axis. But, are you using the DC scale, I assume? Look at the two voltages on a 'scope - that should tell all.
But back to the shortwave bands. How in the world could they have been tuned and listened to while the car is moving? Even with somebody in the passenger seat operating the radio?
He mentioned he hooked up the radio with the tubes out and the vibrator wasn't running and it drew an amp. The speaker most likely has a 6 volt field that draws about an amp of current.
Clifton
:You said that this was a 1941 model, but I note that the schematic is dated 1947. It's possible that some of the differences occurred due to design changes in between those two dates? Here's another thought: assuming the radio was manufactured before the war, repair parts during and soon after the war would have been scarce. Maybe some old-time repairman cobbled together some repair parts (I say old timer, because all the young repairmen went right into the navy).
:
:When you said it had shortwave, I figured it was just the old police band - but this set has HF clear up to 17.8 Mz. I had no idea that car radios were made with such coverage.
:
:Two IF stages, an RF stage, a pair of 6V6s in push-pull, and a dynamic speaker! Were does the DC come from for the speaker's field coil? Usually, in AC sets, the field coil doubles as a choke in the power supply - but maybe this one comes straight off the 6-V battery circuit? I'm wondering if this chassis was adapted from a big, hunky ac-powered radio design? Do you have a car to put the radio in?
:
:Regarding the B+ voltage disparity. If there is any kind of weird waveforms riding on top of the rectifier output, a DMM will behave strangely - even one labeled true RMS. I have a Fluke 179, supposedly true RMS, but it is not - unless the hash is symmetric about the zero axis. But, are you using the DC scale, I assume? Look at the two voltages on a 'scope - that should tell all.
:
:But back to the shortwave bands. How in the world could they have been tuned and listened to while the car is moving? Even with somebody in the passenger seat operating the radio?
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That 1947 document is a belated supplement - the Rider's for it is in vol 12, 1941, and shows the same snubber values. Yeah - I was wondering if someone tried to change to a different vibrator - but I suspect the snubber values have more to do with the transformer - so maybe I should return it to original???
Yes I was excited to see all the important SW bands except for 49m.
It was supposed to get its field coil current from the 6V supply, and B+ just had a resistor, so it was unrelated - but mine has a PM speaker, and it kind of looks original, or at least "very professionally installed".
No car for this one - but I'm excited to have it anyway! And yes it's a high gain radio - 2 IF's! I used a big Astron supply at work because I sold my super high output supply years ago.
I too was awfully surprised to see any shortwave car radios. The next year model was a 985794 - a really stripped down 6-tube radio. This makes me curious whether other manufacturers might have made some - I didn't look into Cadillac or Ford or others yet for this question.
Oh that last comment - I can imagine people were a lot more sensitive in those days about driving a car while fiddling with a radio - so this one is really something different!
Eddie
But, it would be interesting to know if the same year Caddies, Buicks, etc., had the same radio?
As far as I know, the only short-wave models in the GM line were 1941 Buick and 1941/42 Chevrolet.
1941 Buick 5-band model 980660, 8 tubes and synchronous vibrator. Not sure about a short-wave receiver for Buick in 1942, I don’t have any documentation for one.
1941 Chevrolet 5-band model 985697, and 1942 model 985794, both 9 tube radios. I have heard that the Delco short-wave models were manufactured by RCA.
Supposedly Philco made a short-wave converter for the aftermarket and some export models in 1941, a model SW-1 (source: “The Auto Radio, A Romantic Genealogy” by Matteson.). I have seen a friends push-button short-wave converter for post-war Ford export radios.
If one plans to re-cap one of the Delco 5-band radios, be aware that there are paper capacitors inside the antenna and RF coil shield cans (been there, replaced those, an ambitious project!)
Meade
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And what's the clutch and solenoid for? Mine is missing the solenoid - I guessed it was for motor tuning? Mine has all the vital stuff, but it's missing 2 pushbuttons and some of the pushbutton tuning mechanism. But I'm very pleased to have a pre-WW2 shortwave car radio.
Did you notice if your snubber capacitor was .008uF or .001uF??? And its resistor? (Mine were mounted to the 0Z4 socket.)
Eddie
Service information for Chevrolet 985697 is in Riders Chevrolet pages 12-9 through 12-14. There are instructions for coil removal and disassembly. Take very careful notes, especially of the order in which things come apart and the order of re-assembly.
If I remember correctly, the clutch and solenoid operated together when a push-button is pushed. The clutch solenoid released manual tuning shaft, allowing the tuner mechanism to move freely. The larger solenoid then moved the tuning bar to a preset position. All this is from looking at the drawing and from my memory of servicing the radio years ago.
The snubber/buffer capacitor is .008 at 1600 volts in series with the 15k-1 watt resistor, both mounted on the 0Z4 tube socket.
If you don’t find the Riders information, send me an email and I’ll scan the pages for you.
Meade
I still wonder about that "Supreme C-1" vibrator - since I can't cross reference it anywhere.
Next week I might have time to put an oscilloscope on the transformer primary and see whether it runs smoother with the correct snubber/buffer network. I found the Mallory MYE article about vibrators - I just need time to read it.
Eddie