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  #1  
Old 06-26-2012, 09:12 PM
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Magnavox300 Magnavox300 is offline
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Ceramic Disk Capacitor Voltage Help!!

I am restoring a Zenith phonograph amp and replacing everything in it.
The schematic shows the values of the ceramic disk caps, but not the voltage?
How do I know what the .470, .0022, and .0047 disc voltage is on these?
I thought of just going with 250V, since they are for the potentiometers.
But even the .01 discs do not show the voltage value on the schematic.
Anyone know?
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  #2  
Old 06-26-2012, 09:17 PM
bob91343 bob91343 is offline
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500V is common, and they are cheap. No phonograph I know of has voltage any higher than that.
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Old 06-26-2012, 09:36 PM
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Quote:
Originally Posted by bob91343 View Post
500V is common, and they are cheap. No phonograph I know of has voltage any higher than that.
Thanks, I guess I will go with that,
also I know this is probably obvious, but are these UF or PF in Farads?
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Old 06-27-2012, 10:31 AM
bob91343 bob91343 is offline
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microfarads
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Old 06-27-2012, 11:51 AM
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Magnavox300 Magnavox300 is offline
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Quote:
Originally Posted by bob91343 View Post
microfarads
Thanks again for the help!! Okay, I understand the .0022 and the .0047.
There is one disc pictured above that reads "470".
Is that also microfarads?
Finally, there is a disc that reads "270K" "N750".
Is that 2700pf value, or 27UF?
My mind is going trying to figure these discs out!
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Old 06-27-2012, 11:54 AM
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Ceramic disk caps rarely go bad. Replacing them would be futile.
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Old 06-27-2012, 01:46 PM
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Originally Posted by mstaton View Post
Ceramic disk caps rarely go bad. Replacing them would be futile.
Thanks, I was aware of that, the only reason I wanted to replace them was because I gutted the entire amp, and thought it would be fun to rebuild with all new parts. I already painted the chassis, and bought new tube sockets, wire, resistors, etc...
A little crazy maybe, I guess It's just for the fun of the hobby;
I need something to do till I find another set to work on!!

Magnavox300
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Old 06-27-2012, 08:26 PM
comradesvox comradesvox is offline
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Quote:
Originally Posted by Magnavox300 View Post
Thanks again for the help!! Okay, I understand the .0022 and the .0047.
There is one disc pictured above that reads "470".
Is that also microfarads?
Finally, there is a disc that reads "270K" "N750".
Is that 2700pf value, or 27UF?
My mind is going trying to figure these discs out!
See this site for the three digit capacitor codes.

http://www.csgnetwork.com/capcodeinfo.html
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  #9  
Old 06-27-2012, 08:57 PM
bob91343 bob91343 is offline
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The 470 is 470 pF if that's all the marking. Sometimes they use the 3 digit code, which would make it 47 pF but if so there will be a letter suffix indicating the tolerance, K for 10% and M for 20%, but usually even then it's still pF. There is no real standard so you will have to guess. Or, heretical me, measure it.

If you don't have a measuring device, get one, or make one. Simple to do.
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Old 06-27-2012, 10:07 PM
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Magnavox300 Magnavox300 is offline
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Quote:
Originally Posted by bob91343 View Post
The 470 is 470 pF if that's all the marking. Sometimes they use the 3 digit code, which would make it 47 pF but if so there will be a letter suffix indicating the tolerance, K for 10% and M for 20%, but usually even then it's still pF. There is no real standard so you will have to guess. Or, heretical me, measure it.

If you don't have a measuring device, get one, or make one. Simple to do.
Thanks, I still need to get an old condenser tester, heathkit I think I was told was good.
I would also like to get a smaller digital tester.

So I guess I have got all these disc caps figured out now
thanks to everyones help-
For the 270K N750,
I'll just get a 27pf silver mica.
The 47k, I'll get a 47pf silver mica,
and i'm just not sure of the 470 disc,
since it looks just like the .0022, and .0047 UF discs.
I'll order both UF and PF and figure it out when I get the tester.

Thanks again for the help!!
From now on, I will know how to check!

Magnavox300
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Old 06-27-2012, 10:33 PM
bob91343 bob91343 is offline
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No I think the 270K is 270 pF and it's N750 for a reason, temperature compensation.
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Old 06-27-2012, 10:35 PM
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Einar72 Einar72 is offline
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Be sure and get a cap tester with a "leakage test" function. It will show you the most important factor in cap replacement: whether the cap has morphed into a resistor-capacitor combination or just a plain old short. Caps usually don't drift much in value, but a cheesy handheld DMM with capacity and inductance ranges will be helpful if you're not sure what's in the box from the kiddie-labor capacitor factory!

Sorry to see those sweet OEM ceramix end up in the trash - one day you will run into someone who likes to restuff 'lytics and tubular paper caps (not me) and will get lectured about looking stock after a resto...

Good luck with your project, and keep the magic smoke inside every last part!
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