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Old Fluke Multimeters
blue_lateral:
The third one is 4681912.
Dave Wise:
Just following up on the 8060A C19 RMS cap. My main board is Rev H and assembly Rev H.
My C19 is installed matching silkscreen and schematic, that is, plus facing the display and connected to U2 pin 6. Measuring voltage using a hi-Z meter, I see -2mV in DC mode, +5mV in AC mode with a non-overloading 1kHz sine, and +0.5V with 2x overload. So polarity matters but leakage won't be an issue.
I checked my C19 candidates at room temperature. I only tested one sample of each type. Charge one hour at 10V, measure leakage with a 10 Meg meter, discharge 10 seconds, record peak voltage to estimate DA.
Nichicon UKL1E470KEDANA is 9nA and 0.19V (1.9% DA), Chemi-Con ELE-350ELL470MF11D is 5nA and 0.27V (2.7%), Murata ceramic RDEC71E476MWK1H03B is 25nA and 0.70V (7%) - to my surprise, it's the worst as well as the most expensive. Of these three parts, I would use the long life Chemi-Con aluminum electrolytic.
And my beeper boards are on their way!
blue_lateral:
I've had one of the polymer contenders for 8060A C36, Kemet A759, connected to 10.5 Volts for about a day and a half now measuring leakage current at room temperature to see how bad the polymer capacitor leakage really is under the conditions it would probably see in an 8060a laying on my bench. It is connected across the 9 volt battery. If I remember correctly, drtaylor mentioned earlier in this thread that he expected polymer cap leakage to be negligible in the places where electrolytics were originally used in the 8060a. That tracks with these capacitors as C36. Leakage at 10.5 Volts at room temperature is below my ability to accurately measure. It appears to be less than 20 nanoamps, maybe a lot less. I'll probably check a couple more of these as time goes on.
Spec is 120 microamps at 20C, not to exceed 120 microamps at 20C after damp heat or surge testing (see datasheet). Kemet A759 22uf/35VDC , Mouser 80-A759BQ226M1VAAE80 , datasheet here: https://www.mouser.com/datasheet/2/447/KEM_A4072_A759-3316694.pdf
These are almost too tall but do clear the processor board.
blue_lateral:
--- Quote from: Dave Wise on April 12, 2024, 04:51:14 pm ---I checked my C19 candidates at room temperature. I only tested one sample of each type. Charge one hour at 10V, measure leakage with a 10 Meg meter, discharge 10 seconds, record peak voltage to estimate DA.
Nichicon UKL1E470KEDANA is 9nA and 0.19V (1.9% DA), Chemi-Con ELE-350ELL470MF11D is 5nA and 0.27V (2.7%), Murata ceramic RDEC71E476MWK1H03B is 25nA and 0.70V (7%) - to my surprise, it's the worst as well as the most expensive.
--- End quote ---
Could you go into a little more detail about your testing method? Thanks.
Dave Wise:
I don't see what I left out, except possibly the well-known trick of using a voltmeter with known resistance to measure small currents. I put the meter in series with power supply and DUT and let the meter's input resistance be the ammeter shunt. With a 10 Meg meter, 10mV is 1nA. Since I had three DUTs in play, I used three meters, a Fluke 8000A, a Fluke 8100B, and a Monsanto 2000. After measuring the leakage, I shorted the meters. Then I turned off the power supply, which has a few kilohms of bleed at the terminals, and after 10 seconds I pulled off the meter shorts and watched the readings go negative, level off, and fall. This isn't exactly like the IEC standard since the meters load the recovering caps, but since all I wanted was a comparison it doesn't matter. It was quite a surprise to see the ceramic cap perform worse than the electrolytics!
I see that the typical leakage of the polymer caps, like that of the regular caps, is far below the spec sheet limit.
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