Some Basic Radio Stuff

[Drbrown]

Another Barn Member is having Radio problems with his '35 Ford. We have been communicating and I researched and copied to him some '41-'48 Ford Service Bulletin radio testing info in an attempt to help-out.

Understanding that the '41-'48 Service Bulletin info is specific to that time period, I thought that other Barn Members might benefit from the info if only on a general level. So right or wrong here is the discussion:

"The following is not specific to Pre-1941 Ford Radios but may generally be applicable.

A 1941-1948 Ford Dealer's Service Bulletin (#18805) discusses how to test radio antennas using a Ford "Diagnosis Test Set". Since you probably don't have one I am translating their instructions so you can use an Ohm or multi-meter containing that function.

(1) Antenna Short Circuit Test: Turn on and adjust your Ohm meter to read "0". Clip one meter lead to clean-bare metal the car chassis or body - preferably the windshield wiper arm if the radio is installed in the car. Clip other meter lead to the antenna rod which is mounted on car body. A "0" meter reading means antenna is not shorted. Any meter reading indicated a defective antenna.

(2) Antenna Open Circuit Test: Disconnect the antenna lead-in cable from radio. Clip one Ohm meter lead to small tip on the end of antenna lead-in wire. Connect the other Ohm meter lead to the antenna rod. A good antenna will read full-scale (max ohms) indicating continuity from the rod to the cable lead-in wire. Any reading other than full-scale indicates a defective antenna.

(3) Some 1940's vintage radios have an antenna "trimmer screw" conceal behind the tuning knob. Bulletin 18999-B discussed how to adjust it.

A 1941-1948 Ford Dealer's Service Bulletin (#18999) discusses testing/replacing the vibrator, radio tubes, and the testing of the radio current. Generally, current below 5 amps with no vibration indicates vibrator replacement, probable tube malfunction with a specific sequence for testing and replacing the tubes. Current of 6.0 to 6.5 amps is considered normal. Current between 7 and 10 amps indicates replacement of the buffer condenser. Current above these amperages indicates a short in the radio case. Current ratings for particular radios are not available to me but should be found in their manuals.

The same bulletin describes a general testing sequence:

(1) Check fuse. Replace if defective.
(2) Check Vibrator.
(2a) If vibrator appears to be working proceed to test Antenna.
(2a.1) Replace Antenna if defective.
(2a.2) If Antenna okay check for proper current at 6 volts.
(2b) If vibrator does not appear to be working, replace it.
(2b.1) If no reception check for proper current at 6 volts.

Beyond the above level of testing one must identify if the radio has a two or three wire speaker (amp ratings vary) and have the radio and its tubes tested by a radio repair shop.

[Royal Ryser]

A special thank you to Drbrown, who has tried to help me with my radio problem. Fordbarners are great!
Royal Ryser

[Paul Bennett]

I literally cut my teeth on car radio install and repair. Haven't touched one about 60 years but hey ... my dad had a repair shop and I used to make decent odd change in high school and later as a newly wed by going from one used car lot to the next fixing radios for $5 a pop with a few tools and a bag of OZ4s. They all had a car or 2 with a non-working radio and a shop repair was much more and those guys were cheap. Bad vibrator was #1 problem.

While it it easy to write 'replace the vibrator' (2b above) it's more fun and much faster to fix the old one. With vibrator in hand, using a pair of diagonal side-cutters, gently peel back to aluminum lip sealing the vibrator can onto its base. Don't smell the air when you have it apart cuz it stinks. Use a point file to dress the contacts. Replace it in the can, reseal it and test it in the radio. Most every time that rejouvenated vibrator will last another year or several. If the contacts have pitted to major volcanos, you may need to replace the aforementioned capacitor (rare) which has the same purpose as the capacitor in a distributor, neutralizing the inductive elements causing pitting. Let me know how you fare. After all I haven't done one since about 1960.

[Drbrown]

Paul ..... thanks for contributing your knowledge and experience. Its personally rewarding anytime one can fix an existing part to go some extra miles. My Dad taught me that attitude and its stayed with me, even when my wife looks at me cross-eyed when I fix the family's old 1930's GE toaster.

[zeffer1940]

These were good radios, but if u have it out of the car, it would be super awesome if you would replace the big fat waxy filter capacitor (s) they suck up the power and prevent stuff from working very long--just match value and keep pos to pos + It's sort of like putting a new oil pump in old engine..https://youtu.be/gRJd8lwKHeI
https://youtu.be/K1To8tZseVM I also have replace old mechanic vibratrator with a solid state repro--

[Kurt in NJ]

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It's important to adjust the antenna trimming capacitor. Makes all the difference between getting 1 very close station and many
What antenna is being used-- chicken wire in the roof--- under running board --- spare tire or something modern, have the original antenna connections been modified (original is like a small 2 pin bulb, the lead had woven copper shield grounded to chassis