[Patrick]

Hi all,

Can't seem to find an answer. I just picked up a 38-7XX code 121, and noticed a .01 mfd @ 2000v "vibrator condenser. The schematic and parts list just list it as a .01. What can I replace this with?

Thanks,

Pat

[David]

Pat .01mf equals 10000pf  2000 volts you will be looking at a ceramic disc type first place to check would be mousser. David

[morzh]

What is 38-7XX ?

[Patrick]

Pat .01mf equals 10000pf  2000 volts you will be looking at a ceramic disc type first place to check would be mousser. David

Know that,  but my question is about a "vibrator condenser."

[Patrick]

What is 38-7XX ?

Philco console

[morzh]

I realize that. Rider on NA has none of it, and 38-7 is likely something else, so do you have the sch link and the position number of your cap in the sch?

[Patrick]

I realize that. Rider on NA has none of it, and 38-7 is likely something else, so do you have the sch link and the position number of your cap in the sch?

Sorry.

http://www.nostalgiaair.org/Resources/256/M0013256.htm

Same Rider that you have, I'm sure. It's #37, listed as just a .03 mfd. It does look like it was replaced sometime in the past, and there have definately been repairs done. Maybe whoever repaired it just stuck the .01 vibrator condenser in there because they didn't have anything else?

Also, I noticed that #11 is listed as a dual 4 & 8 mfd electrolytic, but there is a single 10 in there. I haven't checked yet to see where the 10 goes, but I guess I should just follow the schematic, pull it out, and install the 4 and 8 in there proper location?

[Ron Ramirez]

The 38-7 does not have a vibrator power supply. It is of conventional design using a power transformer and 5Y4G rectifier.

Part (37) is part of the tone control circuit, and may be replaced with a .033 uF, 600 or 630 volt capacitor.

I haven't checked yet to see where the 10 goes, but I guess I should just follow the schematic, pull it out, and install the 4 and 8 in there proper location?

Yes.

[Patrick]

Thanks Ron,

Really appreciated.

Pat

[K7Sparky]

As I remember it sort of tunes the vibrator like a cap across the points in the distributor did the ignition coil.  Too much C one side of the points burn faster loo little the other side burns faster.

Also suppresses the arc noise from the vibrator.  The inductive voltage spikes are HIGH thus the 2KV rating.

Haven't had a reason to try it but a MOV across the points - parallel with the cap - might help with point burn.  Alternatively might stop the vibrator action dead.  Had mixed results with MOV across large DC contactor coils.  Sometimes helps  Sometimes the MOV holding down the voltage during inductive decay causing a longer decay / drop out time causes timing problems.  The stored energy has to dissipate so lower decay voltage causes longer delay / drop out time.

I found a great vibrator replacement book that had lots of specifications for vibrators.  Among the data was the recommended capacitance.  If you care I will try to find the link again.  Referenced in a post awhile back.

Another good reference from Tubebooks Vibrator Power Supply Design,

[K7Sparky]

OK
What's under the hood?

Seems the model is in question. Is it a DC radio that has a vibrator supply?

[Patrick]

OK
What's under the hood?

Seems the model is in question.  Is it a DC radio that has a vibrator supply?

Check Ron's answer. Thanks for the info.