Identifying Newer Caps

Jeramy Thibodeaux kg4azt at EARTHLINK.NET
Thu Nov 26 16:12:40 EST 2009

282M = 2800pf --- +/- 20 percent tolerance
5J = 5pf --- +/- 5 percent tolerance
50J = 50pf --- +/- 5 percent tolerance
30J = 30pf --- +/- 5 percent tolerance

The letter represents the tolerance of the item.

You also mention that you have alot of capacitors with the capacitance 
marked but no working voltage.  I have only seen this on ceramic discs and 
mylars.  Given the thousands of different capacitors that were available 
throughout the years with the various different markings I am no doubt 
limited by my exposure.  I do however remember reading somewhere quite 
awhile back that these are usually good to 250 working volts, but I 
personally wouldn't trust that.

I can't help you with the plate coupling problem.


----- Original Message ----- 
From: "David C. Hallam" <dhallam at RAPIDSYS.COM>
Sent: Thursday, November 26, 2009 8:13 AM
Subject: Re: [BOATANCHORS-TEMPE] Identifying Newer Caps

> Don't know If I can help, but often J was used to indicate a decimal 
> point.  So, 50J might be a 50 pF.
> David
> David Hollander wrote:
>> I have a box of new doorknob caps with newer (cryptic to me) markings.
>> The working voltage is clearly marked but the capacitance is not.
>> One reads 282M
>> Another 5J
>> Another reads 50J
>> Another reads 30J
>> A bunch of them have the capacitance but not the working voltage.
>> Need a plate coupling cap for my 4-1000 amp I built in the early 90's The 
>> coupling cap in their got fried years ago and is not readable as to 
>> value. What is the suggested value/voltage for the coupling cap? Will be 
>> running around 5KV plate voltage. Want to get this back on for this 
>> weekend's DX contest.
>> Tnx and 73,
>> Dave N7RK

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