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Old Fluke Multimeters

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e-doc:
I renewed another electrotylic cap (10uF / 16V / C21, not leaked but only remaining 3uF), removed the MAC from the socket and washed it in IPA.
I think, it ist much better now, but the problem is not completely solved (-> 2VAC range).

--- Code: ---range     offset
200mVDC  -0.01 to 0.00
2VDC     -0.0001 to 0.0000
20VDC    -0.001 to 0.000
200VDC   -0.01 to 0.00
1000VDC  -0.1 to 0.0

200mVAC   0.00
2VAC      0.0030 to 0.0045, depending on mechanical tension on the input bushings? (not really reproducable)
20VAC     0.000 to 0.001
200VAC    0.01
1000VAC   0.0

200Ohm    0.00
2kOhm    -0.0001 to 0.0000
20kOhm   -0.001 to 0.000
200kOhm  -0.01 to 0.00
MOhm     -0.0001 to 0.0000

--- End code ---


Trying to clean the 2V and 20V range switches (S5, S6) by IPA did not help anyway.

In the end cleaning of the insulation inside the case bottom solved the problem perfectly (I thought, see PS below...).

See manual chapter 5-7:


--- Quote ---                        Caution
Do not touch or contaminate the plastic insulator that is attached to the inside of the case bottom.
When the instrument is assembled the insulator makes contact with the leads on the bottom of the main pcb.
Contaminants could cause undesirable conduction paths.
If the insulator becomes contaminated, clean with isopropyl alcohol.
--- End quote ---

BTW: What an excellent "instruction manual" http://assets.fluke.com/manuals/8060a___imeng0300.pdf. :-+
IMHO better than most of todays "service manuals"...

PS:
The failure came back this morning  (never ending story?).    :palm:

Up to 150 digits offset in the 2VAC range on shorted input.
The display changes on pressing the case top and back together or slightly pressing the range buttons up or down (in front or back direction).

In the end (?) cleaning of the area inside the plastic case around the input bushings solved the problem (let's see how long...).
 



Johnny2Bad:
To Dr Taylor:

Naturally I found this thread extremely interesting reading, and I don't own an old Fluke multimeter (same as many others, couldn't afford one, but now own an 87-V).

In any case, I was intrigued by your early posts whereby you noted that you designed the 8060 specifically with features useful for someone interested in using the meter with audio measurements in mind, and that you did this because of your own interest in audio circa late 70's / early 80's.

while acknowledging that it's clearly off-topic, I was wondering if we could coax you to elaborate a bit on your interest in audio at the time you were crafting the unit that would eventually become the production 8060 series meters?

I promise to respect the thread (and hope others will as well) and keep the off-topic commentary to the minimum (by that I mean after this post, to zero), but would love to read one post from you on the subject.

BMack:
Great thread, loved reading through it. I did have a question I was going to start a thread over but it seems more fitting here, so thanks for the recent BUMP. I found a Fluke D 800 recently and was curious how old it was, I can't even come up with a good guess. I don't know what I'd do with it but for some reason I'm drawn to buy it.

This is not the same meter and not my pic but it's a pic of the same model.

retiredcaps:

--- Quote from: BMack on May 19, 2016, 04:25:06 am ---I found a Fluke D 800 recently and was curious how old it was, I can't even come up with a good guess.

--- End quote ---
Likely 1980 as per

http://www.eham.net/ehamforum/smf/index.php?topic=71868.0;wap2

Chuck at Fluke talks about the D800 at

http://www.fluke.com/fluke/sgen/community/fluke-news-plus/articlecategories/rd/chuck-checks-out-forums-on-test-equipment

macboy:
I know this thread is talking mainly about old Fluke handhelds, but I recently acquired a nice old bench meter, a Fluke 8505A. I don't know the exact manufacture date, but the first printing of the manual goes back to 1983 (33 years ago). This is a 6.5/7.5 digit meter (only 10 VDC range can do 7.5 digit) that is a full width, 3U height rack-mount beast that is as deep as it is wide and weighs just short of a metric-holy-crap-tonne. It uses what Fluke described as "Recirculating Remainder A/D Conversion" or "R2 A/D". That's essentially a 5-bit + sign SAR ADC (five bits!), from which the remainder (error) is sampled, amplified, and fed back for conversion a total of 4 times (in addition to the original conversion of the input itself). The result is a 24 bit (23+sign) conversion. The instrument does >500 of these 24 bit samples/second, and to obtain a noise-free 7th digit, you need to set up each reading to average 128 or more samples, which gives you no more than a couple readings per second. Mine has the Ohms, AC RMS, and GPIB options (yes only DC volts is standard) but is missing the current shunt option that was originally installed. Still a bargain at 100 Canadian pesos (~$75 USD). The manual is typical for 80's era test equipment, having 315 glorious pages full of operating and service info including detailed theory of operation, block diagrams, exploded views, PCB component placement, parts lists, troubleshooting guides, and all-important complete schematics.

If interested, the description of the R2 A/D Converter starts on page 87 (of 315) in the manual downloadable from Fluke (8.3 MB).

I'll try to get a pic up later today.

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