[Eric]

I have a car radio 1947 Mopar made by Colonial 671 (mopar 602) http://www.nostalgiaair.org/pagesbymodel...002867.pdf
My question is part #19 .004 mfd 1500v Can I get away with using 2 - .002 mfd 630v in parallel ? I seem to remember that the voltage rating doubles, is that correct?

Thanks Eric

[Phlogiston]

No.

Two .008 in series, but, the proper cap would be better.

[Radioroslyn]

+1  Russ

>Can I get away with using 2 - .002 mfd 630v in parallel ? I seem to remember that the voltage rating doubles, is that correct?

 No, If you place two .002 mfd 630v caps in parallel what you get is .004 @ 630v. With caps that are the same capacitance in parallel  the capacitance adds but the voltage rating stays the same. If the two caps have different voltage  ratings then it's only good for the voltage rating of the lower rated cap.

In two series of the same capacitance will divide in half and the voltage rating adds. So if you had two 40mfd @ 450v caps in series the total would be 20mfd at 900vdc. When you two caps that are in series  or parallel that are different capacitance the total must be calculated with the proper formula.

#19 has got a lot of ac spikes on it from the vibrator/power transformer that's why it has a 1.5kv rating, I would try to stay at that voltage rating or higher. Disk ceramic maybe a good choice @ 1.5 or 2kv.
GL and have Fun!

[Eric]

Thanks for the input!

[David]

Eric I have some .001 @ 2000v ceramic from a past project if you would like four send me a email with your address and I will drop them in the mail.  David

[morzh]

Eric


When parallelling caps with the same working voltage, the resulting working voltage stays the same. The capacitance is the sum of the two.

When serializing the caps with the same working voltage, the resulting working voltage doubles. The capacitance is then calculated ftom the formula C=(C1*C2)/(C1+C2) which in case of equal values results in half the capacitance of each.

[Radioroslyn]

Or if you are lazy like me:   http://keisan.casio.com/exec/system/1258035746

[morzh]

Does not explain voltages.

Actually another interesting note: when two of the same capacitance caps with different working voltages are serialized, the resulting working voltage is the lower one times two.

That is if you have 0.05uF 200V and 0.05uF 630V caps in series, your result is 0.025uF 400V.

[Eric]

I have put in series 2 .01 630 v caps  my meter show. .005 and I should have a working voltage of 1260v. Now my other problem (s) This has a Positive ground system, while doing voltage checks I'm finding the Filaments are coming in at 5.5 volts but the plate voltages are around 1v. I took a voltage reading @K on the OZ4 and it is 1v. Also on the plates (3&5) of the OZ4 I get 24vac across the two and 12v per side to Chassis. I have no experience on Vibrators, I can feel it vibrate but do not know if it is right.  I tested the tubes and they all passed and recapped.Thanks
Eric

[Radioroslyn]

The likely problem is that the contacts inside of the vibrator are pitted so they have a high resistance. Let's take a few voltage measurements. On the primary of the power transformer from the ct to each end should see 6vdc with the vibrator running. If not contacts are bad, you may be able to cut it open and file or sand them clean to make them work.

Check the resistance on the pri and sec of the pt may by open.

GL

[Eric]

The likely problem is that the contacts inside of the vibrator are pitted so they have a high resistance. Let's take a few voltage measurements. On the primary of the power transformer from the ct to each end should see 6vdc with the vibrator running. If not contacts are bad, you may be able to cut it open and file or sand them clean to make them work.

Check the resistance on the pri and sec of the pt may by open.

GL

ok on the one side of the transformer ( secondary? )  that goes to the OZ4 across pins 3&5 I get 25vac 12.4vac to chassis on each side.
Across the small pins of the vibrator I get nothing (.4mv) Across the 2 large pins I get 3vac 
From the center tap( lower large pin ) and either small pin I get 3vac.
Sounds like the vibrator is bad?

[Eric]

Came across this https://www.tubesandmore.com/products/vi...ive-ground
As this is for a friend who restores cars is this something I should recommend to him for reliability if it the problem!?

[Eric]

Eric I have some .001 @ 2000v ceramic from a past project if you would like four send me a email with your address and I will drop them in the mail.  David

Thanks David but I figure the 1260 volts should work it puts it in the 20% range.

Thanks Eric

[Radioroslyn]

OK Here goes vibrator 101.
A vibrator is a mechanical high speed switch. The two fat pins (pins 1 and 4) connect inside the vibrator to an electromagnet with a reed switch. These contacts cause the reed to vibrate making and breaking the voltage to the magnet. Like an old school buzzer.There are 3 set of contacts all total. The other two have 6vdc pulsating as the reed vibrates between them, this would be the two skinny pins (2and 3). They apply 6v to each half of the PT primary as it's humming along.

If the vibrator is buzzing then the reed and magnet are ok. The problem is the contacts connect to pins 2 and 3. when they are pitted ( like to points in your '38 chevy) it can't transfer the pulsing 6vdc the primary of the power transformer. No primary voltage then no secondary voltage!

You may be able to cut the case open (like restuffing a filter cap can) and file with a fine flie or use some fine grit sandpaper to remove and flatten out the surface of the contacts. Have seen some that where the contacts are just about burn off. In this case you'll need a replacement. As far as I know if you find a vibrator that says 6v on it and has 4 pins you should be in good shape to use it as a replacement. But what do I know????

As for the transistorize ones I heard mixed reviews. I'd stick with a mechanical one if possible. Back in the dark ages some tube testers had a tester for vibrators.

Keeping warm down there in Cumming? It's about 95 by95 here in Pa.

GL

[Eric]

Terry
It's been a hot summer down here in GA 90-95 almost everyday and little rain but it is GA so I take it with a grain of salt 3 months of hot weather versus 6-7 months of winter in Syracuse I think I got the better end of the deal.

Today I will cut off the can to look at the contacts . Came across this sit with along with your explanation helps me understand what is going on in the inside of this thing.

Eric