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Old Fluke Multimeters
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NoisyBoy:
Thanks to bdunham7's generous T1 transformer, the transplant was performed, and another 8000A is back in action!

While the meter works, all the readings are slightly off, so I performed a full calibration today.  For those who plan to calibrate the 8000A, the hardest part is the period adjustment (the first step).  It requires 100ms +/- 5us for the "positive waveform", which really is the "more positive part of the waveform".  The waveform is an unsymmetrical square wave, the lower edge is at about 1.2V, the upper edge is 5.7V with ripples.  What they want you to adjust is the duration of the upper square wave, mine was about 102.87ms.  Most scopes do not have enough precision or accuracy for the adjustment, I use the time interval measurement of my counter driven off of the lab master GPSDO amp, which offers much better resolution and accuracy.  I set it up to trigger to start at the rising edge at 2V, and ending at the falling edge at 2V. 

After that, it is the routine adjustment for each function using a calibrator.  In my case, each pot required tweaking.  But when it is done, the meter was working well within spec.

Note this meter is one of the earlier design, using the 14-segment vs. 9-segment LEDs in my other later 8000A along with a zeroing pot.  A nice addition to the lab.

Again, a big shout out to bdunham7 for helping me out with the transformer, and bringing another vintage Fluke back to full working order.  Thank you!
bdunham7:
Glad to help, and I've also managed to clear up 18 cubic inches of storage space!  For those with an unrepairable 8000A, or one that needs the U3 set like mine, I'll point out that scrapping out an 8000A yields a surprising haul of potentially useful parts.  So far I have:

A nice 0.1R kelvin-connected (properly) resistor, 1 loop of manganin on a mica card
A set of current shunts 1R, 9R, 90R, 900R that seem pretty accurate.
Some nice precision resistors in possibly useful values for a voltage divider--9.9M, 100K, 90K, 10K (several)
A small assortment of mica capacitors
Some vintage op-amps (LM301A for example) and other miscellaneous obsolete semiconductors
A few fairly low quality banana jacks, but they seem to be reusable.

I also have a few interesting capacitors, but the most interesting is from the U3 set, a 0.22uF hermetically sealed type that I couldn't identify.  It has a similar appearance to the integrating capacitors used in other models, but here it is used as part of the circuit that sets the period for U3.  The manual just calls it "Capacitor, poly".  It is labelled "MIDWEC M8-26  .22uF +/-5% 50VDC 415".  I haven't found type M8, although other Midwec offerings seem to have been polypropylene.  Any ideas?



Gyro:

--- Quote from: bdunham7 on January 30, 2023, 07:24:49 pm ---...

I also have a few interesting capacitors, but the most interesting is from the U3 set, a 0.22uF hermetically sealed type that I couldn't identify.  It has a similar appearance to the integrating capacitors used in other models, but here it is used as part of the circuit that sets the period for U3.  The manual just calls it "Capacitor, poly".  It is labelled "MIDWEC M8-26  .22uF +/-5% 50VDC 415".  I haven't found type M8, although other Midwec offerings seem to have been polypropylene.  Any ideas?

--- End quote ---

That's funny, I have one just like it somewhere!  It's the integrator capacitor for the A/D, low leakage and DA. I think mine says it's Teflon but it will be plypropylene at worst.
NoisyBoy:
And the components in it all held up very well, I checked all the eletrolytic caps in my earlier 8000A, they were all within spec, and looked perfect on the outside. 

Granted it is low power application, but having components that lasted nearly 50 years is a testament to its build quality. 

adinsen:
I have an issue with the elastomeric between the display controller PCB and the LCD on my Fluke 8060a. It has deformed/softened over time so it doesn't conduct. The result is missing segments. Unlike most elastomerics this one is cylindrical. I can rotate it by a quarter of a turn to solve the issue for a while, but it rotate back in the old position and then I loose the segments again. I have not seen anyone experiencing this. It seems defective LCDs are more common, but mine is actually fine. I may have missed a post here, though!

Update/edit: I have attempted a repair by inserting a piece of wire in the elastomeric hopefully forcing it to be a bit more round. Pictures attached :)
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