@drtylor
Thank you for your efforts to make such a useful instrument with decent ranges. I didn't even know it until I read your post about these meters. I chose it after I got somewhat disappointed with the new meters. And after I used it, I liked it even more and bought another.
I have a few basic/beginner questions.
1. What are the pros/cons of C28, a 10uF 16V capacitor across VR2, Bandgap Reference Diode. It was removed in the later revisions by you, I presume, but its footprints remain there.
(i installed it and the only thing I have noticed so far is that it has become a bit more sensitive to the touch. Now the digits jump to a higher number when I start sliding my hand up near the V jack in AC function. Other than that I haven't seen any difference in my very limited testing.)
2. If I calibrate the 2V DC range, the 200mV DC range gets affected no matter how little and vice versa. Is it normal or there is something wrong with some component(s). I ended up adjusting both ranges alternatively.
3. What reading of Ratio Test should I consider? It starts sometimes from as low as 9992 and counts up to 9997.
4. How this meter should count up for the LSD? What I am trying to ask here is should the meter show 1.2345 or flicker between 1.2344 and 1.2345 when the actual input is 1.23445 or when the actual input is 1.23449.
The reason for disturbing its calibration pots.
I wanted it to match in reading with my other meter. It was reading about 6-8 counts lower than the other one.
I guess my other meter is better calibrated.
After calibration, its readings perfectly match with my other meter. (The other meter is also an 8060A.)
A little history of the meter in question.
I probably should mention that this is an old meter with serial number 408xxxx. I bought it used about 8 months ago. I have a few guesses about its history. These are
a) It was purchased somewhere around 1990.
b) Sent to Fluke for repair (in 93 as per calibration sticker on it), as its two 1K input fusible resistors were replaced. The calibration seal was intact when I bought it.
c) It was not used much by its original owner because the DF and ESR of all the electrolytic capacitors was well below their maximum values.
What I have done so far.
After reading so many posts about the electrolytic capacitor, I opened it up. The capacitors looked and measured fine as per the United Chemicon datasheets that I could have found for their new series small and the low leakage capacitors. But just to be on the safe side, I replaced them with solid tantalums with as low ESR as I could have found. Their ESR is better than the original Aluminium Electrolytics. I didn't measure the leakage current of these tantalums. I hope it will not be horrible because all the test points are giving healthy measurements.
After replacing the capacitors, I cleaned all the flux residue also from the previous repair made by Fluke.
Then I gave it a long IPA bath. And lately I calibrated its DC function to match my other meter.
It is working fine so far.
Regards,
Qasim.