The PHILCO Phorum

Hello Everyone, just as the title of the thread states, I accidentally broke the lead off of C33A a 3000 pF mica capacitor that was attached to one of the oscillator adjustment padders, and I need to know what voltage I need to go with. Mouser has what I need but I need to know if I need to go with either a 500VDC unit or a 1,000VDC unit, or if it doesn't matter. 

I know normally in a radio restoration you're not really supposed to touch the mica capacitors but in this case I have no choice because the original capacitor didn't have much lead from the factory and when I went to try and reattach the capacitor after replacing the old brass screws that were badly corroded the capacitor lead that was still attached to one of the terminals of the padder control the lead just broke off from all of the stress that it had on the lead over the years. 

Should i go with a 3000pF 500VDC unit or  3000 pF 1,000VDC unit? 
Also should i go with a 1% or 5% tolerance?

Links to the capacitors in question are posted below.

https://www.mouser.com/ProductDetail/Cor...mWfA%3D%3D

https://www.mouser.com/ProductDetail/Cor...VjVQ%3D%3D

Thanks,

Levi

1% 500v is dandy.

Be careful with those. It's not just that one. I've found that, for some reason, the leads on all of those old mica capacitors tend to be brittle. If there's enough of a lead left I've been known to extend a lead by coiling/soldering a wire around the "stump".

Quote:Be careful with those. It's not just that one. I've found that, for some reason, the leads on all of those old mica capacitors tend to be brittle. If there's enough of a lead left I've been known to extend a lead by coiling/soldering a wire around the "stump".

That's a good idea and I would try that but unfortunately the lead broke off at the base of the capacitor where the lead enters the capacitor's body, so there's nothing to attach extra wire to. 

So I just need to order a new replacement capacitor or see if I can find a NOS one on fleabay.

OK so I looked on fleabay and I found a couple of NOS Mica Capacitors that looked like they might work (and are cheaper than the brand new ones on Mouser which they don't seem to have any in stock currently)

eBay Mica Capacitor Link 1

eBay Mica Capacitor Link 2

Would any of these work for my radio's purpose?

Thanks,

Levi

Ok, so would it hurt it any to go up to 1kV on the replacement mica capacitor on this radio as long as its the same MFD value as the original?

I'm asking because I've noticed that the 1kV micas are cheaper than the 500V ones and are more plentiful over at Mouser...  

Generally, you can always replace caps with higher voltage ratings. The downside is it will probably be larger in physical size. The voltage rating of a cap is the maximum working voltage.
Rod

Quote:Generally, you can always replace caps with higher voltage ratings. The downside is it will probably be larger in physical size. The voltage rating of a cap is the maximum working voltage.

Rod

Well I ordered some NOS mica caps from eBay they are 3300 pF El Menco domino style mica caps similar to what was in there originally, I have no idea what the voltage rating is on them, but I'm assuming they are 500V.

My caps came in the mail today, I'm going to be installing one today to see if I can finally get this thing up and running again.

I was able to decipher the color code dots on the capacitors I just bought and 2 of the capacitors are 3300 Picofarad 300 WVDC 5% Tolerance and the other one is 20% tolerance.

The original capacitor was marked as a 20% tolerance capacitor (no color marking on the capacitor for the tolerance marker).

So I figure I will just use the 3300 pF 300 WVDC 5% capacitor in the spot where the old one was because its still within the 20% tolerance specs of the circuit design.

Thanks for your help.

-Levi