Author Topic: Fluke 343A DC Voltage Calibrator Repair Videos  (Read 2309 times)

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Offline TheDefpom

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Fluke 343A DC Voltage Calibrator Repair Videos
« on: May 26, 2017, 01:52:59 am »
Hi all,
Shown below is the first of 2 repair videos for the Fluke 343A DC Voltage Calibrator.

I picked this one up from eBay in "unknown" condition, but someone had obviously been inside it as screws were loose, and a broken standoff was missing from inside the switch compartment... but to give the benefit of the doubt at 40 years old that could of been from anytime in its life.

It is VERY similar to the 341A, the only difference I could identify is the switches and calibration points, the main board appears to be the same.

Part 1:


Part 2 will be up on my YT channel within the next day or so.
« Last Edit: May 26, 2017, 01:58:59 am by TheDefpom »
 

Online xrunner

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Re: Fluke 343A DC Voltage Calibrator Repair Videos
« Reply #1 on: May 26, 2017, 02:03:11 am »
Cool! Will be watching these with interest.  :-+
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Online tautech

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Re: Fluke 343A DC Voltage Calibrator Repair Videos
« Reply #2 on: May 26, 2017, 11:04:00 am »
Pt 2 comes up on Scotts YT channel.


Cool repair Scott, congrats.
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Offline Kleinstein

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Re: Fluke 343A DC Voltage Calibrator Repair Videos
« Reply #3 on: May 26, 2017, 12:14:16 pm »
The 15 V supply also seems to be the reference voltage. So there is no way of changing it to a simple regulator. The reference use looks like an ref. amp chip.
 

Offline Seekonk

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Re: Fluke 343A DC Voltage Calibrator Repair Videos
« Reply #4 on: May 26, 2017, 01:53:48 pm »
I have one of these and it had about half the switch spacers broken.  Some very fragile plastic. That was quite a tricky operation.
 

Online Dr. Frank

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Re: Fluke 343A DC Voltage Calibrator Repair Videos
« Reply #5 on: May 26, 2017, 02:43:18 pm »
Very nice instrument, and good repair.

The 343A is more stable and accurate, than the 341A, and it has 7 digits resolution, instead of 6.
The 343A also has linearity alignment of both decks A and B, whereas the 341A only allows for alignment of deck A. 

Better to replace all these old electrolytics, that might improve noise performance, also.

Some plastics become very brittle after 40 years, so pay attention on the replacement of these spacers.

Would you mind determining the Reference Amplifier type inside your unit, please?
That's Q14, under the black hood, should be near that faulty electrolytic.

Is it already an SZA263, or still the older T.I. DH80417A (or similar designation)?

Thanks.

Frank
« Last Edit: May 26, 2017, 02:51:02 pm by Dr. Frank »
 

Offline TheDefpom

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Re: Fluke 343A DC Voltage Calibrator Repair Videos
« Reply #6 on: May 26, 2017, 06:24:48 pm »
I have one of these and it had about half the switch spacers broken.  Some very fragile plastic. That was quite a tricky operation.

The manual says the plastic is Lexan, or what is also known as Perspex/Plexiglass, or its actual plastics name: PMMA. My unit broke the spacer as it had been badly made, air bubbles can be seen, which means the plastics material had too much moisture in it when it was made, as PMMA is hydroscopic.

Offline TheDefpom

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Re: Fluke 343A DC Voltage Calibrator Repair Videos
« Reply #7 on: May 26, 2017, 06:32:28 pm »

Would you mind determining the Reference Amplifier type inside your unit, please?
That's Q14, under the black hood, should be near that faulty electrolytic.

Is it already an SZA263, or still the older T.I. DH80417A (or similar designation)?

Thanks.

Frank

I will have a look when I have it open again next, I still have to replace the binding posts, and one more of the big 80uF caps.

Offline Jeroen_Bezemer

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Re: Fluke 343A DC Voltage Calibrator Repair Videos
« Reply #8 on: May 26, 2017, 06:55:11 pm »

Would you mind determining the Reference Amplifier type inside your unit, please?
That's Q14, under the black hood, should be near that faulty electrolytic.

Is it already an SZA263, or still the older T.I. DH80417A (or similar designation)?

Thanks.

Frank

I will have a look when I have it open again next, I still have to replace the binding posts, and one more of the big 80uF caps.
You can reinforce the lexan parts by putting some heat shrink tube over it.

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