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| Old Fluke Multimeters |
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| bd139:
Conductance is the reciprocal of resistance. Basically you can use it to measure high resistances (up to 10Gohm), leakage and semiconductor junction characteristics (pop one on a phototransistor for example). If you build the fixture described in the manual you can also measure transistor DC beta and leakage too. Pop the value in calculator and press reciprocal to get ohms back. It makes sense to work in conductance as the scale of the values is different to ohms. If you have the 8012A (I do) you can cal out the probe resistance on 2 wire mode and measure resistance down to 0.001 ohms which is good for tracing out board shorts due to tantalum capacitors! Historically I used to use one with a fixture to classify bags of crappy old germanium transistors to sell to guitar pedal builders :-DD Not bad for an old junker of a meter! |
| 001:
--- Quote from: bd139 on December 05, 2018, 08:10:07 am ---Conductance is the reciprocal of resistance. Basically you can use it to measure high resistances (up to 10Gohm), leakage and semiconductor junction characteristics (pop one on a phototransistor for example). If you build the fixture described in the manual you can also measure transistor DC beta and leakage too. Pop the value in calculator and press reciprocal to get ohms back. It makes sense to work in conductance as the scale of the values is different to ohms. If you have the 8012A (I do) you can cal out the probe resistance on 2 wire mode and measure resistance down to 0.001 ohms which is good for tracing out board shorts due to tantalum capacitors! Historically I used to use one with a fixture to classify bags of crappy old germanium transistors to sell to guitar pedal builders :-DD Not bad for an old junker of a meter! --- End quote --- How do You do it? transistors and siemens :-// |
| GregDunn:
Well, this was a happy Wednesday. Even though I made a couple of puzzling discoveries about my recently acquired 8600A (see other thread in Repair) I was pleased to see a box arrive on my porch, this time a line-powered 8600A in "broken" condition. My goal, as mentioned, is to have at least 2 of these working on the bench, but so far the count was only at 1.5 working meters. >:D Would this one break my unlucky streak? As mentioned above, the broken ones seem to be in better shape than the working ones. :-DD This one was immaculate inside and out except for the missing bail/stand (as listed). I never use them anyway, so the fact that it was essentially un-scarred, especially the faceplate, was a fine tradeoff. Nothing looked obviously zorched or broken. I expected a power supply issue, so I put it on the variac and looked at the +5 and ±15VDC as I brought the voltage up. They looked fine; no excessive current draw, voltages balanced. Well, OK, at least it's not going to blow up. So I brought the variac to 100% and - click, click - the display lit up and relays switched. I did a quick check on Ω with short, open and 1K - all passed, with autorange doing its job. DCV from the calibrator - up to 100V, tracking nicely. ACV from the calibrator - ditto. Now, to the DCA mode. Calibrator output light flickered and meter read 0. That usually means a bad connection (blown fuse?) so I unplugged everything and pulled the fuse holder. The fuse was fine, but the little spring contact was no longer soldered firmly to the board; it was barely touching the fuse. Sadly, I'm going to have to take the meter all apart to repair it due to its buried location, but I'll bet that's why the meter was listed as broken. I'll be very surprised if it fails to work once I've repaired the connection. Not only functioning, but in calibration, as you can see from it measuring the voltage standard of 10.0032 VDC! :-DMM Edit: Managed to solder the spring contact back into place and indeed the DCA and ACA modes work a treat. Hurray for broken $20 Flukes! |
| GregDunn:
Currently working on a "for parts" 8800A which may require a donor unit to revive: https://www.eevblog.com/forum/repair/fluke-8800aaf-power-supply-parts/ The PSU was fixed easily, but it's beginning to look as though the U11 controller is dead - no timing signals even though the clock signal is present at the input. I hate to make this one a donor because it's in excellent shape inside and out, and has the late model Ohms board. |
| GregDunn:
And here's another reason why I buy these in pairs. Just like the 8600A meters I picked up recently, one 8800A was DOA and the other is - fully operational. The hope was that between the two of them I could get one meter working, and that's exactly what I got. This one powered up (as promised) but also seems to meet its specs just fine. DCV and ACV are as good as I can detect, including comparison with the other Flukes. The Ω range also matches my other meters against the PRC resistance "standard" I have. Pretty good for $35. A question for the Flukesters out there: does anyone know what SN the 8800A started shipping with the battery-less ohms board? My 258xxx meter has it, and so does the 286xxx unit. This one is 276xxx and I confess I haven't popped it open yet because it still has a sealed cal sticker from 1999 and I'm not quite ready to tear it off. The fact that Ω is still in spec after 20 years of no maintenance makes me think it's one of the newer boards, as well as the SN being later than my first unit. I will have to open it eventually for inspection and capture another data point, but the question has been on my mind for a while. |
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