Fluke 5440B PSU Fault Check Guarded Power

[dj831]

Hi picburner, sure, I will do (very) shortly! And thanks for your file, but I'd like to compare it with my version (I suspect they are the same). Hence the question : how were you able to read that uC?
My 844USB is not able at all to read Moto UCs, and my ALL-07 could, if only I had matching adapter (ADP-68701) - Matthieu Benoit has no schematics on that adapter, but he has a very old programmer that is able to do readings, a Stag PP39.

Since I'm (a bit) stubborn, I wanna succeed in reading that @*$# processor

Thanks for your input 

[denimdragon]

Hi denimdragon, not sure if you had success in repairing your 5440B. I'm ending in repairing mine, bought 2.5 years ago - no time, but this is something I would have never let go  . Issue of mine was just that .15R resistor on guard that was ... desoldered!

BTW, I had weird issues like yours, after repairing my unit. When it was cold, I had all sorts of errors. There was even a weird noise like a quiet sounding buzzer  . My 5440B had a bunch of these yellow Nichicon capacitors, but two had turned to brown on regulator board (I think that this calibrator ran for week/months or even years without being powered off...).

I've replaced all these capacitors by +125°C on all boards (c.a. the same price than +105°C), and I even increased values (most if not all 22uF were replaced by 47uF - exact same footprint). Since, no more issues, calibrator runs perfectly even if cold (apart stability, of course). I've checked stability after several hours against a 8505 from eBay ($50) and @ +10V, there is a difference of 10ppm between both. And both are rock stable  (of course, this is not a proof in itself).

Note about relays: I had issues too with relays, especially with smallest ones (2 form C). I cleaned contacts without any product, apart with very soft sandpaper (grain of 5000). For other relays, including sanded ones (total of 25 IIRC), I made a small board with an NE556, one half operating @ c.a. 7Hz and the other half being a monostable for c.a. 2 minutes. A kind of self-cleaning. That trick worked like a charm (same trick used with attenuator boards of Tektro TDS 700 series).

I've since dumped nearly all devices - PALs on display controller PCA are readable - and an interesting thing, my calibrator has software v2.1 (most 5440B I've seen are fitted with software v2.0). As I'm in Europe and have the habit of 6 and 9 with tails, I edited EPROM U61 to change display font (reason why I've always hated 4511's ) I will make a separate post about repair and mods of my calibrator when everything is solved (the four remaining things: being able to read 68701, solving 2x20 VFD issue - mine is readable, but not new, replace both leaky output 1uF capacitors, and add four feet).

Thanks dj831! I haven't touch the 5440B since last year but I plan on getting it done now since I have a little free time. Hopefully this weekend I can get back to it especially since I have added an HP 34401A to my meter collection for a totally of 3, plus i want to recap my 3457A and 3456A meter so I'll need the calibrator to be up to spec before I start on those. I'm also looking forward to your thread on getting your 5440B up and running.

[picburner]

My 844USB is not able at all to read Moto UCs, and my ALL-07 could, if only I had matching adapter (ADP-68701) - Matthieu Benoit has no schematics on that adapter, but he has a very old programmer that is able to do readings, a Stag PP39.
Thanks for your input 

Hi,
I have a ALL-07 too but I also missing the ADP-68701 adapter.
However, I have a DATA/IO 3900 also which is able to read and program this device.

[dj831]

Hi picburner, thanks for the info! It seems also that the 2900 does the job too. Meantime, I found everything to build a 68701 reader. Hence, I read my 68701, and I compare to your source code. When done, I post all dumps on xdevs, including equations on the three PALs. When I'm able to get back to work (probably now in may, I guess), I have to scan my SM, since there are differences from known SM, and mine (for example, components list of memory board A15 refers to software 2.1 with modified Fluke references).

Stay tuned

denimdragon: keep in mind that restoring a 5440B takes time and (a lot of) patience, it's hard to fix it in few hours, in-between But you took the right decision to keep it, for sure! Reason why I use confinement time to fix mine. I will measure replaced capacitors and let you know in a next post.

Happy fix

[picburner]

Did you then manage to read the contents of the microcontroller and compare it with mine?

[dj831]

Hi, yes! 100% identical 

Since Ed Oscarson (a very nice guy) was okay to give his source code, I was able to complete the 68701 reader/programmer. You have a picture of my PCB on Matthieu Benoit's website:  http://matthieu.benoit.free.fr/6801.htm (Matthieu has to complete this page with schematics and PCB). This programmer is able to read both 68701 (2kb) or 68701U4 (4kb)

For now, I'm working on 2x20 characters VFD replacement, and on a 'screen saver' that turns off +29V after keyboard inactivity. I will post firmware version 2.1 when xdevs website works (I had issues yesterday when browsing).

[picburner]

Hi, yes! 100% identical

So here they made no changes

For now, I'm working on 2x20 characters VFD replacement, and on a 'screen saver' that turns off +29V after keyboard inactivity.

It is a good idea use a vfd "screen-saver" since in order to get the instrument at the best it must be left on for four hours at least before using it.
So you save a little these precious VFDs.

[dj831]

Hi picburner, denimdragon et al., I've just uploaded minutes ago latest known firmware (v2.1) from my 5440B on Xdevs, including dumps of PALs. Memory dumps are exact copy of my 5440B, meaning that this upload does not include edited version of U61, where I changed font of numbers 6, 7 and 9 to match European fonts (although 7 is more Japanese than European  )

For those upgrading their 5440B, I'm really curious to know what is the difference between versions 2.0 and 2.1

[MadTux]

One difference between FW2.0 and FW2.1 is max output current, at least on my 3 5440As.

FW2.0 has 25mA limit, FW2.1 is 65mA. Apparently there is a resistor on output board, that can be changed, so a FW2.0 board can output 65mA with FW2.1
https://emperoroftestequipment.weebly.com/ (search for 5440A)
Straight swap from FW2.0 to FW2.1 gives a output current limit eror

[picburner]

In summary: changes to be made to use firmware 2.1 and increase the output current.

In the old A4 PCA output board 5440A-1610
                          original resistors:
R7, R8:  80.6 ohm +-1% 500mW 100ppm (CMF651-2-1P80E6)
                            new resistors:
R7, R8: 52.3 ohm +-1% 500mW 100pmm (155069)

But don't blame me if you fry your calibrator

[dj831]

Hi MadTux, thanks alot for that explanation! Just FYI, I had relays issues too with mine, and I made a 'relay clicker' using a 556 to bounce relays @ c.a. 7 Hz for c.a. 2 minutes, worked like a charm!

picburner, you were faster than me  Confirmed minutes ago, R7 and R8 are 52.3 Dale resistors. I don't know (yet) if firmware was pushed on xdevs, but if not, I edit what I've pushed to reflect these changes in attached text file.

Edit: as per marking (T1) and dimensions, matches Vishay/Dale CMF65 series, 1W

[picburner]

Edit: as per marking (T1) and dimensions, matches Vishay/Dale CMF65 series, 1W

The resistors are likely to be 1W, I trusted what was written in the service manual.

Just FYI, I had relays issues too with mine, and I made a 'relay clicker' using a 556 to bounce relays @ c.a. 7 Hz for c.a. 2 minutes, worked like a charm!

I have also had problems with a relay (one 6-way). It took almost a minute to change state and because of this the instrument did not pass the self test.
I bought an identical new one that cost me an arm and a leg.
Then, calmly, I managed to repair the faulty one too.

P.S. Yes, fw2.1 is on TiN's ftp site, I've already got it, thanks.

[MegaVolt]

FW2.0 has 25mA limit, FW2.1 is 65mA. Apparently there is a resistor on output board, that can be changed, so a FW2.0 board can output 65mA with FW2.1

Hardware current protection is made on resistors R5, R3 and transistor Q1 and the same circuit in the second arm.
Replacing the resistor from 80.6 to 52.3 ohms does not affect the ratings of this circuit. (I checked). This means that the protection is triggered at the same voltage drop across the current-measuring resistor.
Those. 65 mA*52.3 Ohm should be equal to X mA*80.6 Ohm
The current limit for younger models is 42 mA. And not 25 mA as indicated in the passport. Perhaps they played it safe by specifying a much lower output current. Or the limitation was software through software measurement voltage on current monitor.

Since it can be difficult to obtain 52.3 Ohm resistors, you can turn an 80.6 Ohm resistor into a 52.3 Ohm resistor by connecting a 150 Ohm resistor (0.5W) in parallel with the 80.6 Ohm resistor. It's much easier to find.

[denimdragon]

So, I'm back at the 5440B again, but this time with a strong resolve. It
is needed for upcoming projects and I actually found a Cal lab that will
calibrate it for a decent price once I get it going.

I was fighting the "PSU Fault Check Guarded Power" error. I replaced the
U2 (LM317) and U3 (LM7915) on A10 board and that error went away.
Now all my voltages are looking good again.

I ran the analogue test and then recevied the "DAC DIGITAL FAULT
Check A TO D". I looked the fault up in the troubleshooting section
of the manual and it say the the ADC failed. I changed out the ICL7109CPL
with a new one and still no love. So now, I'm not sure where to look. I'm
going through the board now and studying the schematics. If any
5440B/5442 owners have ran across this error, what did you do to resolve it?

I'm studying the schematic now to get a better understanding of the
circuit. My next step is to check and see if I have some issues with
the logic side of the board. Dr. Frank mentioned that he thinks I have
a digital problem and he nailed it. It would be nice if the good Dr. could
advise as well.

I have to get this done so Thanks in advance!

[MegaVolt]

Does the device output anything in normal operation? Can you set it to 10V?
It's difficult to guess exactly how he tests the DAC. But since you stopped at the very first test, this means that the DAC may not work at all as it should.
Perhaps you should check the optocouplers; there may be problems with them.

[denimdragon]

Does the device output anything in normal operation? Can you set it to 10V?
It's difficult to guess exactly how he tests the DAC. But since you stopped at the very first test, this means that the DAC may not work at all as it should.
Perhaps you should check the optocouplers; there may be problems with them.

I suspect the optos myself and I will pull them for testing.

The outputs voltages:
1V  = 12.63V
10V= 12.42V
100V= -32.12V
1000V= -40.35

Obviously the are way out. Notably the (-) Voltages.

[MegaVolt]

The outputs voltages:
1V  = 12.63V
10V= 12.42V

To begin with, it is worth considering the low-voltage ranges. A minus in high ranges may be caused by another malfunction.

Once the device produces something, you can start monitoring with an oscilloscope where the signal becomes incorrect. The device's DAC is quite simple. These are two channels of PWM DAC. You need to check:
1. The support voltage must be stable and in the region of 13..14 V
2. Check the presence of PWM on the transistors of each of the two PWM DACs.
3. Check the signal after the DAC.

You will most likely find the problem at one of these steps.

[denimdragon]

To begin with, it is worth considering the low-voltage ranges. A minus in high ranges may be caused by another malfunction.

Once the device produces something, you can start monitoring with an oscilloscope where the signal becomes incorrect. The device's DAC is quite simple. These are two channels of PWM DAC. You need to check:
1. The support voltage must be stable and in the region of 13..14 V
2. Check the presence of PWM on the transistors of each of the two PWM DACs.
3. Check the signal after the DAC.

You will most likely find the problem at one of these steps.

I will check these locations today and report back with
my findings.