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.pdfOperation manual is here
http://www.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_Equipment/Datron/Datron_1061_1061A__1071_Operation_Manual.pdfAny help gratefully received.
RR