Datron 1071 lack of 7th digit with filter on

[rigrunner]

I acquired a poorly Datron 1071 recently. I've found and fixed a few faults that it had but i have one remaining issue that i can't fathom.
I'm hoping that the collective wisdom here will be able to point me in the right direction.

The operating manual says that the 7th digit will be enabled when input filter is enabled.  feedback.loop confirms that his 1071 does enable the 7th digit after approximately 10 seconds worth of samples have been collected after enabling input filter.

The 1071 i have here detects that the input filter key has been pressed. It lights the input filter LED and sends a signal over to the analog board to Q32 energising RL2. The displayed voltages stabilise and it appears that some sort of averaging is being used. The 7th digit doesn't appear no matter how long i wait.

If i enable averaging with the AV button the 7th digit appears after approximately 10 seconds.

I've completed the post repair procedures that start on page 51 section 4 of the service manual and everything checks out ok with the details there, and self tests pass without error.

The faults i've fixed so far are:
    Ranges were a bit screwy -> Analog board replaced Q10, Q23.
    Error 4 when adjusting linearity -> Analog board replaced M23.
    Unresponsive keys -> Digital board replaced M13.

The digital board eproms are 290054-9 and 290055-9 dated 18th May 1984.
Digital board is number 410096-5.
The Analog board is number 410095-5
There are no AC, resistance or current boards fitted.

I have a digital board from a working 1065 that i have substituted the following ICs with no obvious change in behaviour:
M1-14, M16-20, M22-26, M28-29, M32-34, M37-40, M44-49 and M52-57.

I've tried running with later 3 chip firmware for M35, M30 and M18 but none of the revisions i have found will successfully boot.

Service manual is here http://www.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_Equipment/Datron/Datron_1071_Multimeter_Cal_and_Service_Handbook.pdf
Operation manual is here http://www.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_Equipment/Datron/Datron_1061_1061A__1071_Operation_Manual.pdf

Any help gratefully received.

RR

[Mickle T.]

Are you shure you have a Datron 1071 ? 

[rigrunner]

Pretty sure it's a 1071 

The analog and digital boards in your pictures have the same wire through spacer test points as my 1065. My 1071 boards are older have a piece of wire looped over for test points.  Your digital board has  2 x 5101 rams and 2 x  4k drams whereas mine has 4 x 5101 rams.

It's possible that the 7th digit on filter was a later addition to the firmware but i didn't see that mentioned anywhere in the manuals 

RR

[rigrunner]

My digital board

[Mickle T.]

Datron Ins. started to design of model 1071 in 1976 and began to produce the first samples in 1978. According by the presence of CPU reset button, I think you have a old pre-issue 8 device. The cal. manual says: the dithering (7 digits) mode enables only for Av, Input Zero or Cal Zero, but not Input Filter. Thus a 'Rolling Average' mode could not be available on all device issues.

P.S. Still can not understand the optional M18 ROM function 

[rigrunner]

Along with the reset switch i have two other switches that have brown covers with "1" embossed in them. They're not on the later 1065 board either.
If i toggle the switch to the right of the reset button the meter won't boot, if i toggle the one toward the front of the board nothing changes.

I originally thought the M18 was there in case the rom image was > 8K but there is provision for 8k eprom already and the M18 chip has it's own enable line that's driven differently. Perhaps M18 has the code that enables the 7th digit on filter? 

RR

[rigrunner]

Out of curiosity i've just blown a eprom for M18. Iit doesn't seem to make any difference to the operation with it in the meter.

What does make a difference though is having any live mains transformer over or under the analog board. The 6th digit does quite a dance on the lower ranges. That's going to limit shelf location a bit.

RR

[Mickle T.]

What does make a difference though is having any live mains transformer over or under the analog board. The 6th digit does quite a dance on the lower ranges. That's going to limit shelf location a bit.

Yes, this is the well-known Datron 1071 feature. I had to install a metal shield between 1071 and other Datron's and Solartron's in the stack.

[rigrunner]

Blimey. I'd have thought that the two shields inside of the case would have been good enough.
I sat my voltage reference on top of the 1071 and saw the 6th digit was all over the place. For a moment i thought the reference had gone funny,  but it was only happening when the transformer in the reference was over the analog board.
Do you know which part of the circuit is being affected?

Edit:

Just had a another look at the user manual to see where i read the filter = 7th digit info and it's right at the beginning of DC measurements. No mention of certain variants only.


RR

[rigrunner]

As the later versions of firmware don't initialise on my digital board i'd like to try the next revision up from my current -9.

If anyone has dumps of 290054-17, 290055-17 and 290116-17 i'd appreciate copies please.

RR

[dacman]

Have you tried cleaning the pins on the ICs that are on the digital PCB or have you traced the signal?

[rigrunner]

I've tried cleaning and substituting ICs on the digital board.
The input filter button is read by the digital board and actioned by sending the signal to switch on Q32 on the analog board, but no 7th digit without average enabled. 

At the moment i'm thinking that my 2 chip firmware doesn't have the code to enable the 7th digit with the input filter.

RR

[Mickle T.]

Well, I did it.

[rigrunner]

  Brilliant. Thank you

I'll give it a whirl in a little while and see if it runs on my board 

RR

[rigrunner]

With the -17 roms fitted the meter displays junk and hangs 



Time to try and find a later digital board.

If anyone has a digital board 410096 from a 1061/62 1071/72 or 1081/82 with a suffix >= -9 going spare please drop me a PM.

RR

[vf33184]

I have Datron 1071 with this old CPU board, with version 9 installed, unfortunately when I bought it, one EPROM on CPU board was dead. So far I tried to upgrade both CPU anf GPIB boards to version 20 what I have sourced from newer hardware revision of 1071 (different CPU and GPIB board). After upgrade meter is working but just with GPIB board disconnected. When I connect GPIB board to CPU board then it is not working at all (the same behaviour as was mentioned by rigrunner), seems that this new firmware is not backward compatible with old hardware.

I have checked the version 17C files what were uploaded by Mickle T. but I believe that those 3 files are only for CPU board. One note here: old CPU board has 2x2532 and 1x2716 EPROM chips, however newer CPU boards have 3x2532 EPROMS. As I understand there must be always matched firmware between CPU and GPIB board so it would be great if Mickle T. could upload also v17 software for GPIB board.

Another option is to get version 9 set, or at least single file for my dead EPROM is 290055/9 (position M30), TMS2532. My understanding is that rigrunner) could have those files.

Thank you.

-vf-

[rigrunner]

Hope these are helpful.

[Mickle T.]

As I understand there must be always matched firmware between CPU and GPIB board so it would be great if Mickle T. could upload also v17 software for GPIB board.

Sorry. I don't have Datron DMMs any more. 

[vf33184]

As I understand there must be always matched firmware between CPU and GPIB board so it would be great if Mickle T. could upload also v17 software for GPIB board.

Sorry. I don't have Datron DMMs any more. 

Oh, that's pity. It seems that you have been the only one in the world who has seen version 17 for older Datron 1071 version. Is there any chance to back track where your Datron ended up and ask new owner for help?

Thank you.

-vf-

[vf33184]

Hope these are helpful.

Thank you very much, those version 9 files look promising. Yesterday I have ordered few TMS2532s from ePay, but it will take some days to arrive. Then I will try to program full version 9 set and see if it works.

Btw, you have been searching also for an upgrade. Did you succeed? Or you found newer version of CPU board supporting also newer version of software?

Please let me know. Thank you.

-vf-

[mslr]

Hello, I'm actually in the process of bringing an Datron 1071 back to life - it is also a very old board with an add-on PCB for the RAM. Looks to be version 17c regarding firmware. Has GPIB option - does a copy of the EProms help you? Let me know.

Picture of the digital board with replaced tantalums attached.

[vf33184]

Yes, it looks that your CPU board is almost identical as mine, can be a bit newer than mine (your display board is labeled with -6 at the end and my is -4). If you check EPROM 290114-17C and it will be AM2716 or TMS2516 (not TMS2532) then it should be compatible with my board.

It would be great if you could copy all 4 EPROMs, 3 from CPU board and 1 from GPIB board. These are always matched together.

I am adding pictures of my CPU and GPIB boards.

Thank you.

Note: TMS2516 and AM2716 are equivalents, but TMS2532 and TMS2732 have different pinouts. Be aware when you setup your programmer to read it. Modern programers support 2732 but usually don't support TMS2532 or its equivalents.

[vf33184]

Finally purchased TMS2532A's arrived and I have programmed SW version 9 what was uploaded by rigrunner. That is 3 EPROM version, 2 chips at CPU board and 1 chip at GPIB board. And this version works perfectly in my meter. 

I have also programmed chips with SW version 17C what was previously uploaded by Mickle T., that package consist 3 EPROMs for CPU board (newer firmware is bigger), unfortunately GPIB EPROM image is missing. I left GPIB board disconnected and tried the meter. It seems that basic functions are working, however when I try to enable Input Zero or Input Filter then it hangs up. 

When I got the meter, it was not working at all and repair was not so simple. Apart of one broken EPROM, I also had to replace damaged EPROM socket, Motorola CPU was faulty, one resistor array had an issue with one of internal resistors and 10uF/350V capacitor in power supply was dead too.
 
For now it seems I have working meter at least with SW version 9.  If complete SW package of version 17C will be found (maybe by mslr), definitely I will try it. In a meanwhile I have to find out why I am getting Error 7 with selftest (resistance board) although resistance measuring itself is working. When resolved I will also perform full calibration.    EDIT: Error 7 is not resistance but AC voltage problem.
 

[doktor pyta]

Thanks for the info.
I recall that Error 7 was often caused by wrong position of 2W/4W switch on the front panel.

[alm]

Indeed, the self test only works with the switch set to 2W mode, from what I remember. It will fail if the switch is set to 4W.