Author Topic: Old Fluke Multimeters  (Read 187694 times)

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Offline smmi

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Re: Old Fluke Multimeters
« Reply #700 on: August 11, 2019, 04:47:07 pm »
hey ogdento...  sometimes we get lucky... sometimes we don't...

that's a big cleanup job on that meter... thank goodness for modemhead's blog and dave taylor's comments up here - for me anyway... and geez what happened to the alt-power battery eliminator jack's input cover? - is that from the spewed electrolyte?... that big blob of green on the MAC certainly seemed telltale...

after I recap this 8060A, I'm going to tear into my 87 (a knock-around spare I've had for years) and clean the display's zebra strips so it gets dark-dark again - I hope that's all it is... 99-isopropyl is our friend... good luck...

Offline ogdento

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Re: Old Fluke Multimeters
« Reply #701 on: August 11, 2019, 07:17:16 pm »
Very true Smmi!

Turns out that blob of blue/green on the chip is actually paint - Modemhead's got a ceramic chip in one of his 8060 repair entries with a similar blob.  And I think the power input jack is actually OK, the plastic is a little rough but I think flash did it a grievous injustice ;)

I really like the 87s too... I forget that they're 30 years old!  Great meters, easy to work on, and I love that the service manual is so inclusive.

Offline Dave Wise

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Re: Old Fluke Multimeters
« Reply #702 on: September 01, 2019, 04:01:32 pm »
As I said in post #650 of February 13, 2019, I have an 8100B that read slightly high.  I was able to bring it spot-on with a slight tweak to R175 ZERO.  I'm still curious about the other ADC adjustments (R308 TRIP POINT, R149 REMAINDER), but it's pretty useful as is.

I don't see a separate thread for differential voltmeters, so I'll say here that I just got a tube-type 825A/AG back on its feet.
This model is a premium version of the 801B with a 1mV null detector vs 10mV.  The /AG means the reference is a Zener instead of a standard cell.

Unusual cap failures: a leaky electrolytic that depressed a regulator, another leaky electro coupling cap causing null detector offset, and an electro that was pretending to be a battery.  I rarely see a leaky low-voltage electrolytic that causes a malfunction, usually they just dry out.

Unusual cap, that failed: Why did Fluke use a paper/oil bumblebee?  In a sensitive spot in the regulator?  While the rest of the film caps are mylar?

Also a rectifier with photodiode action causing more-than-full-scale offset on the recorder output.

When I accidentally applied high voltage on a low range, one of the polystyrene input filter caps gave its life to protect the neon that was supposed to protect it.  But after one hour in total darkness, the neon fired at 92V so it just must have been the cap's time to go.  Not having a 0.1uF polystyrene, I used polypropylene.

The plastic number wheels were warped causing them to rub one another making the action rough.  This probably afflicts the 801B and other models that use them.  I fabricated good-looking replacements using the original metal hub, a cut-down CD blank, legend overlay designed in LibreOffice Draw, and self-stick plastic laminating sheet.  They look great, and the knobs slip from one detent to the next with that smooth ringing clank like they're supposed to.  I'll post the recipe if anyone wants.

The switch contacts were dirty, but they quieted after a shot of polyphenyl ether.

I was beginning to compare it to my gold standard 895A when the latter failed.  Not my favorite scenario.
But it turned out to be simple, just an open electrolytic in the 1100V Reference Supply, parts are on order.  Four Nichicon UCA-6 (short and wide) 22/450.

It's been a good week.

Dave Wise

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