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Cap Tester question


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4/27/1999 1:05 PM
TAP
Cap Tester question
Can you guys give me your wisdom as to buying a capacitor tester? Ie. what models work well and what features do I need? I see these things on e-bay occasionally, but I have no idea which are good/bad.  
 
Thanks a bunch,  
 
tap
 
4/27/1999 2:42 PM
Gus
a sencore lc 102 will test leakage up to 1000 volts, da, esr, and value most cap testers in dvms only test value. IMHO a min tester should have value and leakage. In cap testers you get what you pay for.  
 
Gus
 
4/27/1999 4:10 PM
jason

I second the sencore.  
jason
 
4/27/1999 9:18 PM
Steve A.


tap:  
 
    Are you looking for a dedicated cap tester- or just a decent DMM that will measure capacitance? I'm not sure what other test equipment you already have for working on tube amps, but the money spent on a dedicated cap tester might be better spent on something else (like a scope?). The capacitance functions on a decent DMM have been adequate for most AMPAGE-type stuff.  
 
Steve Ahola  
 
P.S. Long before I ever had a DMM that could measure capacitance I would test HVAC run caps for opens or shorts with an analog ohmmeter. The needle would flick towards 0 ohms and then slowly recede to infinity. Reverse the leads and the deflection would generally be twice as much. The ohm scale on a DMM works the same way, only you have to read the numbers fast. If the reading does not eventually go back beyond the range of your meter then there is some serious leakage in the cap. But I can't say how well those techniques would work for the smaller caps used in tube amps (the smallest HVAC run cap I've ever seen was 2uF).
 
4/29/1999 7:24 AM
Paul Perry

How a cap fails:  
open circuit.  
short or partial short.  
looses all or some cap.  
still has cap, but equivalent series resistance thru the roof (electro).  
 
So unless you are doing a LOT of cap testing, I think the best tester is a cap placed in parallel with the 'suspect'...  
 
I'm assuming that what you are doing is looking at faulty gear, not testing parts from a junkbox.
 
4/29/1999 10:15 AM
TAP

Thanks guys for the advise. I think I'm probably going with what you suggested SteveA. And since I'm starting out I could spend my money on better things (scope, signal gen, etc).  
 
BTW Steve, what DMM would you (or others) suggest getting with the capacitance function?  
 
tap
 
4/29/1999 10:27 AM
Carl

Don't laugh but Radio Shack makes several DMM's that aren't bad. I have one in my field service kit that I bought for about 70 bucks. Mine has worked flawlessly fof several years now.  
 
It's auto ranging, tests caps diodes, transistors, AC/DC volts and amps, frequency, continuity and has a temp probe(can be really useful at times). You can't beat the warranty on them either 5 years and they'll replace it even if you throw it off a cliff.  
 
Let the flames begin!!!!  
 
Carl
 

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