1937 Radio Repair

[frank37]

I have a radio in my 1937 LaSalle that was restored 20+ years ago which has suddenly stopped working. I used to hear the vibrator sound when turned on but it is now silent. I know its getting 6volts having taken the cover off  and turning the unit on--at least one of the tubes lights up; gently tapping the tubes didn't help.
   Can anyone advise on who would be expert enough and reliable to fix this radio?
Thanks  FPezzimenti

[bcroe]

The vibrator needs somewhat frequent replacement in these radios.  It generates
the chopped voltage to make 250VDC for the tube plates.  Check which type you
have, likely 6V pos ground, 3/4 pin or a 5/6 pin synchronous.  There are solid state replacements for these that don't vibrate much, but a synchronous might
take some rewiring.  Bruce Roe

[jackworstell]

Our 1937 series 60 had the original Wells Gardner 5X radio....is that what you have  ??   It had a synchronous vibrator which..... of course..... was bad.

There's a place in Florida that makes solid state substitutes but they could not help me with this particular vibrator.

But I found two other sources that worked.   

We also has to replace all capacitors and have a guy to do an electronic alignment at the end.   But thankfully the transformers, speaker and tuner were all OK       

Jack Worstell

[bcroe]

Our 1937 series 60 had the original Wells Gardner 5X radio....is that what you have  ??   It had a synchronous vibrator which..... of course..... was bad.

There's a place in Florida that makes solid state substitutes but they could not help me with this particular vibrator.  But I found two other sources that worked.   

We also has to replace all capacitors and have a guy to do an electronic alignment at the end.  But thankfully the transformers, speaker and tuner were all OK. Jack Worstell

That is about the way it goes for serious repairs.  Glad someone knows how
to spell synchronous.  If a good 6V synchronous vibrator can't be found, the
radio can be converted to use a 6V, 4 pin vibrator with a couple silicon diodes
wired as the rectifiers.  This will also allow either a positive or negative ground.
Bruce Roe

[jackworstell]

Bruce.....  two years ago when I was trying to figure out how to replace the synchronous vibrator
in a Wells Garner 5X ( 1937 Cadillac series 60) I found two solutions that worked....both involving solid state electronics.

One solution was to buy a SS vibrator and two diodes from www.everythingradio.com     ( their designation for the vibrator was VBP-1 and for the diodes was ECG 125.......but I think this was just their internal nomenclature )

So are you saying that if I wanted to switch the radio from positive ground to negative ground all I would have to do would be to flip the two diodes around ?      And I guess reverse the wiring on the SS vibrator...I believe it is polarity sensitive....

Jack Worstell

[bcroe]

Bruce.....  two years ago when I was trying to figure out
how to replace the synchronous vibrator in a Wells Garner 5X ( 1937 Cadillac series 60)
I found two solutions that worked....both involving solid state electronics.

One solution was to buy a SS vibrator and two diodes from www.everythingradio.com     
(their designation for the vibrator was VBP-1 and for the diodes was ECG 125.......but
I think this was just their internal nomenclature )

So are you saying that if I wanted to switch the radio from positive ground to negative ground all I would have to do would be to flip the two diodes around?      And I guess reverse the wiring on the SS vibrator...I believe it is polarity sensitive....   Jack Worstell   

The problem is finding a good synchronous vibrator, NOS or solid state equivalent. 
This type radio will always ground the vibrating element, since ground is the common
point between the low and high voltage circuits.  Can't be sure without checking on
non synchronous.  A pair of properly rated diodes can do the job of the second set of
contacts, and will always select the proper polarity regardless of battery.  So the diode
anodes will connect to ground and the cathodes will go to the trans secondary windings. 
That can be done by wiring them under the vibrator socket, or in a 6 pin plug into the
socket. 

That done, an 3/4 pin vibrator can be used.  The first problem is plugging it in, either
its mounted on a 6 pin plug, or the radio socket is changed.  Guess an adapter could
be built with enough clearance. 

The second problem is polarity.  A mechanical vib doesn't care, but a Solid State does. 
I don't know what 6V polarities are available.  The same SS vib could be used for the
other battery input, IF you turned the vibrator circuit UPSIDE DOWN.  Not such an
easy job, because these are very short and heavy wires.  Some tie directly to the
chassis.  None of this vib wiring can allowed to gain much length or get out of the
complete metal shielding, or it will radiate and interfere seriously with reception.  A
radio with diodes and mechanical vib will work on either polarity, like its vacuum
rectifier cousins. 

It would actually be possible to build one solid state vibrator that would work on
6V or 12V, either polarity.  Then the only issue would be fitting a 3 or 5 pin plug
for almost all radios.  But with the extra cost and extremely limited market, it
doesn't seem worth the investment to build it. 

I saw a vib replacement circuit that just uses a couple big transistors with the
trans as a multivibrator.  Don't do that, as it saturates the trans, probably
heating things up, drawing more power, and running at a lower switching freq
that may come through to the radio.  The SS vib should have a frequency
determining driver ckt independant of the output transistors.  Bruce Roe

[frank37]

As a postscript---I found a new vibrator and that turned out to be the problem.  My radio is the stock Delco GM radio with a 4 prong vibrator.   Saved me from having to send the whole heavy unit out for repair.  Its an easy fix--just plugin and play.   Thanks to all those who responded.  Frank Pezzimenti