Author Topic: [Volt-nut] Zombie F5720A calibrator build out of random boards.  (Read 7283 times)

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Offline TiN

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One who did not build own calibrator from random crap cannot be called true volt-nut.

Back in 2014, when I was naive and overly optimistic, I thought it would be piece of cake to build a DIY MF-calibrator. There is still a thread as evidence of that. Fast forward to 2018, I've learned quite a bit, build over 30 LTZ1000-based references, accumulated lot of expensive not-necessary equipment and even got somewhat working 5.5-digit Time Electronics 9823 calibrator.

However friend of mine introducted me to real deal, Fluke 5700A, and since we peeked inside of it my soul was gone.

Only owning very personal 5700A can restore the status quo. As with usual volt-nut disease, first sign is suddle - I thought why not buy A11 REFDAC board from 5700A, that will give me finished and proven dual LTFLU-reference and DAC eh? Just add some RPI, power supply and level translation, some python code, and we can get module to generate some precision voltages, eh?

Well, shortly after I got ohm boards.... then I discovered that to power these things I will need about 6 different unipolar rails. Well, after XXXX $$$ spent over last 2 years I have now all 5700/5720A boards, some in multiple quantity. I even scored Fluke 5500A front panel, which I hope to modify to fit 5700A VFD display board.

Today I received last bits - A3 and A4 backplanes, so this project is to kick off from waste of moneys and dust collectors to hopefully something workable.



Now the only "issue", I don't have a chassis. So far my best thinking is to make CNC plates from Aluminum and build something like a crate to hold all things together, in arrangement same as real-deal 5700A.
Who need chassis anyway, eh?



To be continued.

First I need to restore cables with connectors on transformer and check baseplane boards and outguard power. Then we can continue to inguard power and then start adding boards as progress goes.
« Last Edit: May 22, 2018, 01:54:40 am by TiN »
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Offline TiN

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Re: [Volt-nut] Zombie 5700A
« Reply #1 on: May 16, 2018, 03:27:32 am »
First smoke tests, just out-guard section.  :-/O



This is how it looks like. Rather tricky to position everything stable enough, because if heavy weight of transformer and it's steel frame.  :phew:



After few mishaps with front panel power and mainboard connector not matching the service manual schematics, I got it powered on
No communication error from outguard. I wonder why, heh.  :-DD



Now we go ahead for more involving tests.
« Last Edit: May 20, 2018, 12:16:53 am by TiN »
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Offline TiN

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Re: [Volt-nut] Zombie 5700A
« Reply #2 on: May 16, 2018, 03:36:35 am »
RSVD for complete runs.
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Offline Vgkid

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Re: [Volt-nut] Zombie 5700A
« Reply #3 on: May 16, 2018, 04:15:54 am »
Looking forward to this epic build.
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline Andreas

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Re: [Volt-nut] Zombie 5700A
« Reply #4 on: May 16, 2018, 04:40:09 am »
Crazy    :-+  :popcorn:
 

Offline quarks

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Re: [Volt-nut] Zombie 5700A
« Reply #5 on: May 16, 2018, 04:44:07 am »
I am always amazed what you show us, looking forward to see the final outcome
 

Offline GerryBags

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Re: [Volt-nut] Zombie 5700A
« Reply #6 on: May 16, 2018, 05:30:21 am »
 
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Offline Pipelie

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Re: [Volt-nut] Zombie 5700A
« Reply #7 on: May 16, 2018, 11:48:17 am »
Livestream for first smoke tests pls. :popcorn:
 

Online Echo88

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Re: [Volt-nut] Zombie 5700A
« Reply #8 on: May 16, 2018, 04:46:35 pm »
Inspired by your mentioning of the A11-REFDAC-stand-alone-possibility i also aquired a A11 a few years ago.
I have the necessary power supply about half way ready and already tested the Arduino-code to control the 82C55 and 82C54 on the A11. Assembling kinda slowed down after i received my Fluke 5440b Calibrator.  :=\
 
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Offline HighVoltage

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Re: [Volt-nut] Zombie 5700A
« Reply #9 on: May 16, 2018, 05:57:58 pm »
Your work is amazingly impressive.
Thanks for sharing

There are 3 kinds of people in this world, those who can count and those who can not.
 

Online BFX

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Re: [Volt-nut] Zombie 5700A
« Reply #10 on: May 17, 2018, 04:37:03 am »
 :popcorn: :box:
It looks like nice new story  8)
 

Offline Navarro

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Re: [Volt-nut] Zombie 5700A
« Reply #11 on: May 17, 2018, 07:05:40 am »
TiN always beeing TiN.

One day Fluke will see it and throw some piece of gear on your house.
PY1CX
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Offline zhtoor

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Re: [Volt-nut] Zombie 5700A
« Reply #12 on: May 17, 2018, 08:43:03 am »
is Fluke's backyard in Taiwan?  :D
 

Offline hwj-d

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Re: [Volt-nut] Zombie 5700A
« Reply #13 on: May 18, 2018, 09:06:42 am »


A real "Frankenstein"  :-DD :-+
 

Online nikonoid

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Re: [Volt-nut] Zombie 5700A
« Reply #14 on: May 19, 2018, 01:34:15 pm »
Awesome thread! Thanks for sharing.
I am convinced that you will not stop when it is finished to original spec, but start looking for ways to make it ever better.

I am subscribed.
 

Offline TiN

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Re: [Volt-nut] Zombie 5700A
« Reply #15 on: May 20, 2018, 12:25:50 am »
I decided not to lurk around and go right for the business.



Now it's important to note, that I was working on my calibrator boards in background for last year or so, and all of these boards are already repaired and working except A18 regulator supply and high-voltage power supply board. I was lucky to have friend with 5700A that I have here in service now (A12 and A7 issues), so I got a chance to verify my boards one by one (obviously except power boards, not going to risk it).

So while it may look stupid plugging all 23 boards together for first tests, I actually have confidence that 91% of them working OK already. Question was only about A3/A4 and getting it all together.

Quick check on VFD brightness.



VFD glass is dim and aged, but we have a future solution for that. It is good enough for current states, so no worries.

Shall we try bold attempt on running self-test?  ;D



It takes about 15 minutes to have calibrator self-verify itself, using internal LTFLU, 10K and 1 ohm and Fluke FTS references.
I don't have WBV option modules plugged in yet, it's too early for that.



She passes!   :-DD  :popcorn:



I also run the DCZ internal self-calibration. It did not spit any errors either.



Based on today's progress, I think we have a progress  :=\
Soon will need to start designing CAD drawing for chassis metalwork parts. First step would be to make each assembly rough 3D model, so I can make it all "fit".
« Last Edit: May 20, 2018, 03:12:01 am by TiN »
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Offline branadic

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Re: [Volt-nut] Zombie 5700A
« Reply #16 on: May 20, 2018, 01:12:44 am »
If you have the 5700A of a friend in house it should be easy for you to copy the metal sheet parts into CAD and get them lasercutted and bend, right? I'm sure you find very cheap lasercutter at your location.

-branadic-
Prema 5000 | Prema 5017 SC | Tek 2465A | VNWA2.x with TCXO upgrade and access to: Keysight 3458A, Keithley 2002, Prema 5017 SC, 34401A, 34410A, Keithley 2182A, HDO6054, Keysight 53230A and other goodies at work
 

Offline TiN

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Re: [Volt-nut] Zombie 5700A
« Reply #17 on: May 20, 2018, 08:00:22 pm »
Happy Metrology Day 2018 everyone!  :-+ :-DMM



 :popcorn:
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Offline Messtechniker

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Re: [Volt-nut] Zombie 5700A
« Reply #18 on: May 20, 2018, 08:10:37 pm »
Finest metrology porn at its very best.
Really gets me started :scared:
Agilent 34465A, Hameg HMO1022, R&S HMC 8043, Voltcraft VC 940 and M-Audio Audiophile 192
 
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Offline Tony_G

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Re: [Volt-nut] Zombie 5700A
« Reply #19 on: May 21, 2018, 03:34:32 am »
Random question TiN, what is that white thing in the upper left with blue tape on it? Is it just a light?

TonyG

Offline TiN

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Re: [Volt-nut] Zombie 5700A
« Reply #20 on: May 21, 2018, 03:58:22 am »
Yes.

Troubleshooted A14 high-voltage control assembly today. Found few dead zeners which are not zenering anymore, and cooked high-voltage 10pA Ibias opamp, that drive the PA assembly, which in turn drives the high-voltage transformer.
Need to buy replacement for it, that is OPA445BM. $24 a pop, happily DK have them in stock.
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Offline TiN

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Re: [Volt-nut] Zombie F5720A calibrator build out of random boards.
« Reply #21 on: May 22, 2018, 02:00:43 am »
Got some pretty PCBs to play with.

PCB A: Expanders for DIN backplane connectors, to electrocute myselftroubleshoot stuff during calibrator operation.



PCB B: Thermal spreader PCB that sits on the back of A10 main resistance board on original Fluke 5700/5720A's. A10 which I got from ebay was stripped of this shield board, so I build my own version.
It is 4-layer, with solid copper plane on 3 outside layers. Side facing the board is isolated.



I got plenty extras, so I can even modify few to use as front protection cover above for resistors. I don't want to ruin those ceramic hermetic networks by accident, those are unobtaniums.



And compare to original Fluke one (tinned board on the right), which is 2-layer (metal only on outside).

I don't know about you, but I like mine better.  :box:



There is also PCB C stuff, but that to be unveiled in due time.

« Last Edit: May 22, 2018, 02:03:58 am by TiN »
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Online Echo88

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Re: [Volt-nut] Zombie F5720A calibrator build out of random boards.
« Reply #22 on: May 22, 2018, 08:20:12 pm »
 :D Looks like the VFD-replacement.
 

Offline TiN

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Re: [Volt-nut] Zombie F5720A calibrator build out of random boards.
« Reply #23 on: May 23, 2018, 10:06:51 am »
Echo88
Heck no :)

Extender in action:



Anyone interested in each board overview?  :-DD

Today I received spare A9. Just couldn't resist.  :-//



The Ohms Cal assembly (A9) contains the 1 Ohm, 1.9 Ohm, and zero short resistance values. It also contains a digital control stuff, and a 2-wire compensation circuit for of two-wire ohmmeters cal. A differential amplifier circuit and a 2V/5V/10V source from this board also are used during calibration of the ohms function. Also lot of latching DS2E/DS4E relays ;).



Board made in 2004, sporting newer green better quality PCB. Shield removed for clarity.



The floating supplies for U7 and U8 consist of a dc-to-dc converter made up of LT3526N PWM regulator (do not confuse it with modern LTC3526!), transformer T1 and associated components. Switching-regulator control IC U6 switches +17S through the primary of T1 at about 30 kHz as determined by R27 and C21. The secondary of T1 is
rectified and filtered by CR1, CR2, CR9, CR10, C22, and C23. The voltage is then regulated by 8.2V zener diodes VR1 and VR2. Additional filtering is provided by L3, L4, R43, R44, C24, and C25. Two capacitors (C53 and C54) between ACOM and SCOM reduce switching noise that would otherwise appear across the calibration resistor.

You also can see primary 10KOhm (ceramic hermetical network), sneak in between relays. This is the resistor that gets calibration vs external 10 Kohm during ACAL. Four of these resistors are used in my voodoo prototype Fluke SL935 to form precise 10KOhm.



The 1W value is made of four 4 Ohm wirewound resistors in parallel (R41). The 1.9 Ohm value is made of two 3.8 ohm wirewound resistors in parallel (R42). Relays K4 and K5 connect the 1 ohm and 1.9 Ohm values to OHMS OUT HI and OHMS SENSE HI. Relays K6 and K30 connect them to OHMS OUT LO and OHMS SENSE LO. Relays K7 and K8 select the short. There are low and high-side current cancellation circuitry too.




« Last Edit: May 23, 2018, 10:09:10 am by TiN »
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Offline hwj-d

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Re: [Volt-nut] Zombie F5720A calibrator build out of random boards.
« Reply #24 on: May 23, 2018, 02:30:08 pm »
Ok, ok, you've convinced me. Now i'm looking on ebay germany, if I can get these pcb's for a small amount of money too...   :-DD
 


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