no power?

[radio nut]

so what would cause a 470mf cap to test ok on a heathkit cap checker ,but be way off on the 470 mf part reading only 32mf. is this cap starting to "open"?

[radio nut]

Well, I put the standby board on and.....drum roll please.....it works! Ya! Gotta put it back together now...but Yeah!!. Thanks for the help!

[radio nut]

here it is!

[ChrisW6ATV]

Originally Posted by radio nut

so what would cause a 470mf cap to test ok on a heathkit cap checker ,but be way off on the 470 mf part reading only 32mf. is this cap starting to "open"?

470uF is a large value electrolytic capacitor. I wonder whether such large values can be reliably "measured" on capacitance meters. It is not something I ever tried. Much more valuable with electrolytics is to test their ESR, effective series resistance. That part probably has high ESR, and would be easily identified as bad on such a meter.

Excellent news that you got the set working again!

[powerking]

You mentioned testing this cap on a "digi-bridge". What is that; perhaps one of those cheapy Chinese digital ESR all-in-one type testers ? I assume that after all this discussion in this thread you did finally get an ESR meter?


Tom(PK)

[radio nut]

The digi bridge over at fair radio is a every expensive digital bridge for checking values of resistors and caps. Oh,on the ESR ....there were 6 buldged caps on the main power supply board that checked fine with an ESR, but tested junk on a Heathkit cap checker. So for right now I will not get an ESR meter. I have worked on vacuum tube stuff for years, but not modern TV,s. If I want to use an ESR I will just take the board in question to fair radio and use there a.

[radio nut]

My problem with the ESR is in this case 6 caps tested good, actually the ESR showed the 470 MF cap as good. The american made bridge showed it as only being 32MF after rremoval. So in this case the ESR was wrong 7 times.
now, maybe the esr is a cheap manufactered poor quality meter...that may be the case. if a high qaulity esr would function better then ok, i will have to get one.

[powerking]

My "guess" is this digi-bridge instrument is just a high accuracy -component out of circuit- only Wien bridge based device. Most all ESR meters out there currently are non-Wien bridge based and use a high frequency test signal (~~ 100Khz sine wave) to effectively measure the A.C. impedance of a capacitor. Also, they only output ~~ 100mV or so in that they don't activate any PN on NP semiconductor junctions; another reason they are so handy for in-circuit testing. Yes the ESR maybe a fraction off in-circuit VS out of circuit but you're looking for a gross discrepancy when using these ESR meters. Take a 100uF cap which measures say 50 ohms and the spec should be less than 0.1 ohms; light bulb event; Houston we have a problem; LOL).

So it's not surprising how you got misleading results on the tested caps in-circuit VS out of circuit on this "digi-bridge" tester; expected behavior??? If I'm wrong, others will "correct" me.

Tom (PK)

[radio nut]

Thinking about it in all fairness the ESR used only had a good/bad scale and the caps checked did fall on different sections of the good scale. Maybe if I had read the directions or been taught by a professional on its use first then maybe the same value/voltage caps testing (maybe good ) but closer to the bad range would have been a red flag to impending doom. The complaint was that the set would not turn on at all. 6 of those caps were on the main board and would not stop the set from turning on.
Maybe "my" ESR complaint is that I have not gotten the feel for.....or understand how to use it correctly.
the "6" caps were bulged and needed to be replaced .
The 470 mf cap was the one keeping the set from turning on..
So now I am curious, Do the ESR meter owned by members here have a pass/fail scale or are they more advanced?

[radio nut]

This is the final pic!

[ChrisW6ATV]

That is an interesting experience with the ESR tester. I have only used ones with an analog meter, marked with a scale in ohms as well as minimum values for "good" capacitors of various sizes. So, a 1000uF part could read nearly full scale but it would be bad on such a scale.

[radio nut]

maybe this one had an ohms reading and since i did not have the directions or specs on caps, maybe it was showing them as questionable.... need to learn before i make snap judgements!

[davet753]

When I spent my days troubleshooting, my ESR meter cap checker was the best thing since bottled beer. While it was not 100% accurate, it saved so much time it was worth the occasional false good readings.

[Findm-Keepm]

Originally Posted by davet753

When I spent my days troubleshooting, my ESR meter cap checker was the best thing since bottled beer. While it was not 100% accurate, it saved so much time it was worth the occasional false good readings.

Ours paid for itself many times over. It was the one piece of test equipment that never let us down either! 80 bucks to buy, and it saved hundreds of hours of troubleshooting.

Cheers,

[ChrisW6ATV]

The few times I got a "false good" reading with my ESR meter at work was when I happened to have a capacitor in a circuit with a low-value resistor in parallel, or in a case where several capacitors were in parallel and not all of them were bad.