Original 6V Radio Reception (Pos. Ground)

[Al W]

I had the original radio rebuilt for my 1938 Desoto R/S Coupe - Philco Transitone C-1550.  It bench tests fine, but installed in car the reception is extremely weak and volume very low; however, when I touch antenna it comes in clear & good volume. I checked OHMS of antenna and read anywhere from 1.6 to 2, which I believe is good - it also worked before antenna was installed on car and the antenna was touching seat frame???? leading me to believe that once grounded all would be good).  I also ran a ground wire from antenna base to positive battery terminal (positive ground car) with absolutely no improvement. I'm at a loss - any help would be appreciated.

[Guest]

You may want to contact your rebuilder and/or check the factory service literature, as there is likely a trimmer (capacitance) adjustment on the radio to electrically match the antenna to the radio circuitry.  This adjustment usually has to be made upon reinstallation of the radio after repair and is usually an external adjustment through an access hole from the outside of the radio housing.  

 

If you can't find any information in the factory literature, try the Sams Photofact literature that the radio repair techs used back in the day.  An internet search using the radio brand and model number will likely find the correct Sams issue covering that radio.  Good luck.

[Frank DuVal]

5 hours ago, Al W said:

I checked OHMS of antenna and read anywhere from 1.6 to 2,

Where are the two leads of the ohmmeter when you got a 2 ohm reading?

 

From center pin to outer (grounded) part of the plug should be infinity ohms, typically shows OL (open loop) on Fluke meters.

[Frank DuVal]

BTW, this chassis is in Rider's Volume 9:

 

http://www.nostalgiaair.org/Resources/957/M0013957.htm

 

Antenna trimmer adjustment (padder adjustment) is on page 9-54. Instead of a signal generator, just tune to a weak station near 1400 kc (now known as KHz 😉)

 

Looks like padder adjustment is on the main tuning capacitor inside the radio. Maybe there is a hole to insert the small screwdriver.

[Al W]

So I rechecked as you said and meter said O.L which I assume would be open loop.  The 1.6 to 2 ohms reading was from touching center pin with one lead and touching base of antenna on car - I tried that again today and got a more constant .3 OHMS (I was more careful today not to touch the leads while doing the tests - would that matter?).  My father bought  car in 1970 & radio in 1971.  He had everything except the Chrome Dash plate which I was able to locate recently - my dad is 91 years old and I really want to be able to take him for a ride while listening to the AM 'oldies' - it's been a 50 year wait!  If I touch antenna while standing on ground (barefoot) radio plays absolutely perfect.

 

Edited July 14, 2021 by Al W (see edit history)

[TerryB]

So how fast can you run? (Just kidding).  It does sound like the radio needs some antenna trimming.  Your body acts as a capacitor so that might be a hint.

[ILIKECARS53]

AL W,    Can you share who rebuilt the radio.  I would like to have the one in my 1942 Buick rebuilt but have heard all kinds of comments both good and bad on the the rebuilders out there.  Thanks  Jim

[Ohjai]

A good source for old radio information can be found at  

 

https://www.radiomuseum.org/

 

Jim

[ILIKECARS53]

Thanks.  Will check them out.   Jim

[Al W]

SOLVED - Thank you, Frank DuVal.  Antenna did indeed need to be tuned to radio.  This was done by turning the ‘Skyway/Roadway’ antenna selector.  Very slight adjustment made an incredible difference.  Radio is working perfectly now with great volume & tone range.

[Frank DuVal]

Ta Da!👍