Author Topic: Fluke 5200A AC Calibrator Repair Videos - In Progress  (Read 2286 times)

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Offline TheDefpom

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Fluke 5200A AC Calibrator Repair Videos - In Progress
« on: September 26, 2017, 05:45:34 pm »
I am in the process of repairing this old Fluke 5200A AC Calibrator, this is the first video in the series, I already have footage ready for part 2, and part 3, which I will be publishing soon also.

 
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Online texaspyro

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #1 on: September 26, 2017, 09:45:37 pm »
The 5200A uses a RC oscillator (I think it was 10 MHz) to generate the clock.  Mine was rather wonky.  I replaced it with a DIP-14 TTL crystal oscillator.
 

Offline 3db

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #2 on: September 26, 2017, 09:58:03 pm »
@texaspyro
Was the original a sine wave ?
 

Online texaspyro

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #3 on: September 26, 2017, 10:26:22 pm »
What ever it was, it fed TTL.  It was around 15 years ago...

At one time I did a PCB to make an extender cable for the 5200A boards.   I used a pair of 50 pin ribbon cables.   The same PCB is used on each end.  For the edge connector, I used one with wire wrap pins and bent the pins and soldered them to the edge tab on one of the PCBs.  I have never used it (never had a need).  I am a bit wary of it since some of the backplane slots have like +/- 300V on them... a bit high for ribbon cable.  I did check it with a 1000V insulation tester and it passed. 
 
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Offline Dr. Frank

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #4 on: September 27, 2017, 02:30:16 am »
The 5200A uses a RC oscillator (I think it was 10 MHz) to generate the clock.  Mine was rather wonky.  I replaced it with a DIP-14 TTL crystal oscillator.

There's one tuned LC - oscillator, to generate digital 10MHz for the PWM of the DAC, which generates a variable precision DC reference voltage of about 0.3 .. 3V, out of an SZA263. That's really great old school stuff.

The programmable / variable output frequency of 10 Hz .. 1MHz is generated by a quadrature RC oscillator, which has nothing to do with these 10MHz...
The output amplitude of this analogue oscillator is compared to that DCV reference and regulated to exactly the same RMS value by a fast precision rectifier. Also great stuff.

Although this design is pretty old, it's really precise and stable, if repaired properly.

Good luck, DefPom, that it's been the PSU subassembly P23 only.
That fat TO-3 component is a 5V regulator, 3A or 5A, not a transistor, and hopefully ok. (*)
The other transistors might still be available, or have compatible new parts.

Frank

(*) It's obviously an LM123K, a 5V, 3A regulator, still available, or replaceable.
« Last Edit: September 27, 2017, 02:44:48 am by Dr. Frank »
 
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Offline Tony_G

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #5 on: September 27, 2017, 02:52:18 am »
I bought this as the extender for working on my 5200A - Mine is currently stable but the quadrature output isn't accurate so I need to get back in and work on that at some point.

eBay auction: #222653463018

TonyG

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #6 on: September 27, 2017, 04:30:36 am »
Thanks for the feedback, I do have the power supply repaired, I show that in part 2 and part 3 (which I haven't published yet), it still has issues, one of the +-15v power supplies which is linked to a reference supply is outputting the wrong voltage, I need to dig into that more, there is no output, and is showing overload continuously, again I haven't dug into those yet, but suspect a -190v regulator fault.

Offline Tony_G

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #7 on: September 27, 2017, 09:54:00 pm »
My overload problem was actually with the oscillator (I can't remember if it was the oscillator or the control board). I happened to have a good board so I just swapped it out and that fixed it.

I never looked into what the board fault was unfortunately.

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Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #8 on: October 02, 2017, 04:21:41 am »
Part 2 video:

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #9 on: October 10, 2017, 07:15:08 am »
Part 3... its going to be a loooong series.


Offline tautech

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #10 on: October 10, 2017, 07:36:36 am »
 :scared:
Oh hell, I've only watched Pt1 so I've got some catching up to do.

I enjoy such drawn out detective stories Scott, so keep it up and I hope it all ends well.  :)  :-+
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Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #11 on: October 10, 2017, 07:56:18 am »
I had to dig out my 8842A 5.5 digit meter to do some precision measurements on resistors... but I could use a 6.5 digit in my equipment list (cough, siglent, cough free, cough)
« Last Edit: October 10, 2017, 07:57:52 am by TheDefpom »
 

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #12 on: October 13, 2017, 06:45:47 pm »
Part 4... it's going to be a long series.

Offline fcb

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #13 on: October 13, 2017, 07:27:05 pm »
I've got a pair of 5200A's (one is black plastic handles and one is metal handles).

One is pretty spot on, the other isn't.  So I look forward to watching the your videos when I have a few spare hours!

I've also got a 5215A, but I dare not power that up until I've had the lid off it and bought an HT probe (it has +/-2500V rails inside).


Offline Bill158

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #14 on: October 15, 2017, 07:17:01 am »
Part 4... it's going to be a long series.


You really have a "tiger" by the tail on this one.  Part 4 of your video seemed a little "disjointed".  You were working on the basic power supplies and then suddenly you were working on the A12 Reference Board.  Then it goes back to the basic power supplies and then you are disassembling the A12 Reference Board and working on that one again.  But I was able to follow once I saw Part 4 to the end.  I am glad you got a clear and correct manual for the 5200A.  I have one and it does differ somewhat in the areas you are working on, i.e. the A12 Reference Board.  As you have discovered R-45 on A12 is a 85.75 WW Card resistor which probably has a T/C of something like 10 ppm/C (or better).  Since this sets up the basic output voltage of the Reference Amp U30 eventually you should find something that has a very good T/C.  The value probably isn't all that important as long as it is around 86 ohms because you have R-48 which will give you some latitude in setting the final voltage of the Reference.  I hope that none of the other "matched" resistors for the Reference Amp are damaged.
I was confused at the end of Pt. 4 as to where you had the FLUKE meter hooked up when you were getting around 6.985 volts.  Are you on the input of U29 or U33?  But then you seem to be looking at the basic power supplies again and not getting what you expect.  You realize that the A12 Reference Card supply is to set the precision AC output of the 5200A and I don't think has any effect on the basic power supplies.  However I could be wrong here and will have to look at the whole circuit.
One other point that was in Part 1.  You seemed to be confused as to the exact function of CR-11,12 and 14 in the A5A2 Power Supply Assembly.  Those are "current regulator diodes".  See the 1N5283 through 1N5314 JEDEC parts.  The are N-Channel JFETS with the Gate hooked to the Source.  This is the basic IDSS testing configuration for a 3 terminal JFET.  The purpose of these CR diodes is to get the pass transistors Q12, Q9 and Q8 started up until the output voltage reaches the desired value set by R22/R23 for the -30V, R18/R19 for the +30V and R14/R15 for the -15V supplies.
Just trying to help you here, good luck!
Bill
 

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #15 on: October 15, 2017, 07:34:31 am »
Thanks for the feedback.

Yes I was going back and forth a bit there, I thought I had the power supply sorted, but then realized it still wasn't right, as the +-15 and +20v rails weren't correct even when plugged into the main unit for the reference voltage for the opamp.

The reference supply uses the+-15 and +20 v supplies, and then generates the 6.9v reference, which is fed back to the power supply board as an opamp reference, and this regulates the opamp to generate the +-15 and +20v rails, however that wasn't working because of the faulty resistors and I the blown opamp.

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #16 on: November 04, 2017, 09:17:48 am »
Part 5 (sorry I published this about a week ago but forgot to put it here)


Online texaspyro

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #17 on: November 04, 2017, 10:01:50 am »
Spend the $7-$20 to get one of those "component testers" that are all over the place on Ebay.  It will do a hell of a lot better job identifying and checking transistors and caps than a DMM.  You just connect the part (up to three leads), press the button, and voila... you get a picture of the part with the terminals labeled and its parameters.  Some darlington devices / power transistors with internal resistors can fool it.

My preferred model is the "AY-AT" version with a socketed processor chip, color LCD display, and rotary encoder.
« Last Edit: November 04, 2017, 10:03:35 am by texaspyro »
 

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #18 on: November 04, 2017, 10:07:32 am »
I have various testers, all I am checking for is opens/shorts on the components, and the fastest way is with the dmm, if I need more information or a proper check I use my Peak transistor tester, you will see it used in some of the videos.

Online texaspyro

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #19 on: November 04, 2017, 10:17:56 am »
I've seen LOTS of transistors that check out fine as two diodes, but utterly fail as transistors.  You can then spend hours debugging the circuit because you thought a bad transistor was good because the DMM diode check passed.  It pays to actually check the parameters of all your devices... particularly if they are in sockets.   Oh, and never trust an in-cicruit measurement.
 

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #20 on: November 09, 2017, 02:20:50 pm »
Part 6


Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #21 on: November 21, 2017, 09:01:46 am »
Part 7, I recorded this a month ago, I haven't had the chance to get back into it yet, as I have been too busy with more important projects.


Offline apelly

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #22 on: November 22, 2017, 08:03:54 pm »
I picked up one of these with a kaput power supply a while ago. Haven't had time to look into it yet, and these things do seem to be bears to fix, but if you're in AKL you're welcome to borrow it and try swapping some boards/comparing values.
I'd rather a Google clue, link, or some theory than "do this" (generally)
 

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #23 on: November 22, 2017, 09:26:33 pm »
I picked up one of these with a kaput power supply a while ago. Haven't had time to look into it yet, and these things do seem to be bears to fix, but if you're in AKL you're welcome to borrow it and try swapping some boards/comparing values.


Thanks for the offer, I will see how I go once I get sufficient time to start going through the boards in a logical manner, I will get in touch if I get stuck and need to do comparisons.

Offline TheDefpom

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Re: Fluke 5200A AC Calibrator Repair Videos - In Progress
« Reply #24 on: December 13, 2017, 02:47:40 pm »
I finally got some time to get back onto this project, here is part 8 of the series:



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