Author Topic: Fluke 8000A DMM Schematic  (Read 338 times)

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Offline Vonsgarage

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Fluke 8000A DMM Schematic
« on: March 01, 2021, 02:14:53 pm »
Good day to you all.
Just finished this redraw and would like to share with you all. Note this is the battery version schematic, Option -01.

The PDF's I used are too large to include in this post. I will add them another time. They are handier than the originals I downloaded as I changed them to text searchable and several other nice changes.

I am sorry to report that the schematic redraw is not text searchable. Every setting I have tried results in the schematic becoming big-time fuzzy. Rats; back to the drawing board!

Some Notes:

•   All work based on two different manual downloads from the Internet. The one I used for primary reference is P/N 347906 and dated March 1976 Rev. 1. 5/79 and lithograph copyrighted 1982. The second source document has one single date shown on the last page: “Rev. 3. 8-73”. I did not use this older version as the schematic had obvious errors: i.e., citing range switch settings based on “1” rather than “2”.

•   There is no legend. Fluke didn’t provide. For example; what’s the difference in the ground point triangle symbols? One with a line; one without? On the line powered only unit, they are shown interconnected. On the battery unit (Option -01) they are not shown interconnected. I traced out the power-line ground and added that to the schematic.

•   Not sure where the unregulated +5 is used.
•   R15: part of the Period / Turnover adjustment. One schematic indicates one leg of this pot tied to ground; another schematic shows it tied to minus 15VDC. Tried to trace out to no avail without a lot of disassembly.

•   Power Supply: there was a line shown on both source schematics that made no sense being there; I changed it to dotted line. Also added C24 as my unit had it installed and one of the manuals did list it.

•   The “Ohms Overrange Voltage Limit” section on the original schematic was outlined and cited as “Option -04”. Documentation on this option is non-existent.

•   My DMM has the “Milli Amp Sec” option. There is no option number or circuitry information listed anywhere in the documents I have. The PCB used for this option is screened “8000A/MAS4001 / 450239 REV 0” and is quite complex. It is located where the Low Ohms PCB would have been installed.

And finally some questions. Has anyone fooled around and figure a circuit mod to change out the NiCD to NiMH battery charging circuit? I love this ole' timer and the old battery system is the only thing I'd like to change. Also, has anyone access to the schematic for the "Milli Amp Sec" option?
The following users thanked this post: coromonadalix, NoisyBoy

Offline NoisyBoy

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Re: Fluke 8000A DMM Schematic
« Reply #1 on: March 01, 2021, 06:50:18 pm »
I have a broken 8000A with Option 01 sitting in storage for a couple years now.  I hope to get it out and work on it this summer, your schematic would be most helpful in my effort to revive the old DMM.

Coincidentally, I just did an annual cleaning, adjustment and inspection on my other 8000A (without the battery option).  It is amazing to see even the original caps are still within spec after 40+ years. 

If I am able to revive the other 8000A, I would also like to change the battery to NiMH as well.  So I would be curious to see what you find out.

Thanks again for your contribution.

Offline Vonsgarage

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Re: Fluke 8000A DMM Schematic
« Reply #2 on: March 02, 2021, 11:57:51 am »
I also have a 8000A that has stood the test of time. The +/- LED flashes back and forth with zero volt input. That's pretty cool. Precision voltage source verifies it is still spot on calibration. I tweaked her up a bit. Replaced the input jacks with safety type and added battery holders for the NiCD's. I will keep you in mind if I figure out a battery mod. I also have always wanted to replace the MAN72 LED's with the HP version that is shown on some of the documentation I have found. Much snazzier look.
Glad to provide the new drawing. I am practicing using Paint.Net.

Offline coromonadalix

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Re: Fluke 8000A DMM Schematic
« Reply #3 on: March 02, 2021, 03:30:07 pm »
maybe add some li-ion bms circuit with the cells ??

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