Forum,
Is there any extensive expertise out there on these new modern marvels. Cleaned the points on the old electro-mechanical part, and its running at 111cps with a bad pwr xformer, but how long will it last with a good xformer. Are these new SS parts as good as the old electro-mechanical parts. Its a Mopar 802 from a 49 Dodge, and appears to have negative ground according to radio schema.

marv

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Hello Marv,

the solid state vibrators work well and appear to be much longer lasting than the previous electro-mechanical versions. I rebuilt my 52 Hudson Hornet radio with one and had no problems at all. That was 14 yrs ago. Radio still playing great.

Forum,
:Is there any extensive expertise out there on these new modern marvels. Cleaned the points on the old electro-mechanical part, and its running at 111cps with a bad pwr xformer, but how long will it last with a good xformer. Are these new SS parts as good as the old electro-mechanical parts. Its a Mopar 802 from a 49 Dodge, and appears to have negative ground according to radio schema.
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:marv
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49 Dodge 6 volt system is a positive ground car. To use a solid state vibrator it would have to be one for positive ground. The use of a mechanical vibrator the polarity would not make any difference.

I have found the importance of replacing the buffer cap when servicing a vibrator power supply due to possible shorting. These need to be in the order of 1600 wvdc. A shorted buffer cap will quickly kill a vibrator and I have come across a few that have shorted.
I haven't had much luck with SS vibrators and have successfully reconditioned used mechanical ones. Maybe the SS ones don't quite match the requirements of military filament and B+ power supplies like the PP-308.
The manufacturers don't supply an internal schematic diagram or mechanical equivilent diagram of the replacement SS vibrator, just the application data.
Many times the vibrator can can be opened carefully and the contact points cleaned up. The side-to-side duty cycle can be balanced with a meter or scope on the bench by gently bending the reeds. Internal wiring can be modified to change polarity and configuration requirements.

Warren,
Now I'm really confused.The Ryders schema for this radio shows a +V at the dc input, but if that is not correct, its not the only error I've found.

marv

:49 Dodge 6 volt system is a positive ground car. To use a solid state vibrator it would have to be one for positive ground. The use of a mechanical vibrator the polarity would not make any difference.
:

If you look up any 49 Dodge, Plymouth, or Chrysler they were all 6 volt positive ground. I had a 53 Chrysler It too was 6 volt positive ground.

:If you look up any 49 Dodge, Plymouth, or Chrysler they were all 6 volt positive ground. I had a 53 Chrysler It too was 6 volt positive ground.
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In my teen years I had a friend who worked at a salvage yard; he gave me all the car radios I wanted. (Some I still have, but unfortunately I scrapped many of them for parts, or sold them.) Anyhow, for these old MoPar (and GM) radios, in stand-alone operation, it does not make any difference at all whether the positive or negative is 'grounded' to the radio chassis. In fact, the radio works fine if you short the vibrator, passing current to ONE SIDE ONLY of the vibrator transformer, and feed the radio with 6.3 VAC; you will need availability of 5 amps or more at 6.3 VAC. I put numerous of these and other grand old car radios in a sturdy wood box, with a speaker, and an old TV transformer, and sold them. They would rock the house! Some are still going to this day. EdM

I opened the orig, and filed the tits off both sets of points, then polished with emery cloth. Assumed the Swiss file would slightly bend the contacts, but the damn thing came up running at 111 cps, (per spec) with a dirty waveform. It continued providing system power thru out all tests, so gave it a dubious OK. Will replace it labor free, with a SS part, if it fails within a few months.

marv

::If you look up any 49 Dodge, Plymouth, or Chrysler they were all 6 volt positive ground. I had a 53 Chrysler It too was 6 volt positive ground.
::
:In my teen years I had a friend who worked at a salvage yard; he gave me all the car radios I wanted. (Some I still have, but unfortunately I scrapped many of them for parts, or sold them.) Anyhow, for these old MoPar (and GM) radios, in stand-alone operation, it does not make any difference at all whether the positive or negative is 'grounded' to the radio chassis. In fact, the radio works fine if you short the vibrator, passing current to ONE SIDE ONLY of the vibrator transformer, and feed the radio with 6.3 VAC; you will need availability of 5 amps or more at 6.3 VAC. I put numerous of these and other grand old car radios in a sturdy wood box, with a speaker, and an old TV transformer, and sold them. They would rock the house! Some are still going to this day. EdM
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