Fluke 8060A display processor replacement

[bborisov567]

I got yhis old Fluke with a bad processor. There is some short internally in the processor because it is overloading the supply line from the MAC.
This results in the display flashing. When i externally supply 3.3 V to the processor it stays on constantly but there are missing pixels. Clock signal is ok.
 Both elastomeric rubbers are ok. Second picture is with only 3.3 V applied to the processor. I am pretty sure the pixels on the bottom left should be on.
I couldn't really find any information about the communication between the MAC and the processor. My goal is to make a new display processor so that
i can use the multimeter. The only information i can find is in the service manual (page 108) :

"Four-bit parallel data bus between u3 and U5.
During the first part of a data transfer operation
they carry the address of the register being
read or written to. During the remainder of the
operation they carry data."

Has anybody done tis procedure?

Link to the manual: https://assets.fluke.com/manuals/8060a___imeng0300.pdf

[Martin72]

Hi,

We(company I´m working for) still having a flawless and yearly calibrated 8060A here.
Can make pics from the display after turning on(or other pics if desired, just tell it).
It got 100Khz trms bandwith so it´s worth to spend some time for repair.

[bborisov567]

I believe that when turned on all pixels show up as test, right? Not FFFs like mine.

[Martin72]

I forget to check it today, do it on monday - But as far as I remember, it wouldn´t be FFFF.

[Martin72]

At 21:08 you can see what the display shows after switching on...

[Tomorokoshi]

There are a few good threads here that cover the Fluke 8060A, including one with the original engineer. I will check on that video later. My 8060A/AA occasionally locks up, and it only clears if I turn it off and on.

[bborisov567]

Yep, i definately have a bad microprocessor.

There are a few good threads here that cover the Fluke 8060A, including one with the original engineer. I will check on that video later. My 8060A/AA occasionally locks up, and it only clears if I turn it off and on.

I tried using the search on the forum but didn't find any information regarding the microprocessor and display. It seems that only my unit has this problem. I forgot to mention something else that is bugging me. When i try to measure the clock frequency parallel on the quarz i get only noise on the scope(measuring at x10 not to load the curcuit). But at the same time there is 40kHz clock at the output to the processor and also 2.5kHz for the continuity beep. Both frequncies are generated from the main clock, according to the service manual. Am i doing something wrong while measuring the quarz?

[Tomorokoshi]

Here are some threads that may help:

The original engineer:
https://www.eevblog.com/forum/testgear/old-fluke-multimeters/

Manuals with schematics:
https://www.eevblog.com/forum/repair/service-manual-for-fluke-8060a-multimeter/

Restorations:
https://www.eevblog.com/forum/testgear/fluke-8060a-repair-doa-meter-brought-back-to-life-pictures/
https://www.eevblog.com/forum/repair/mostly-fixed-fluke-8060a/

The capacitance of the oscilloscope probe probably stops the crystal.

[Zoli]

...
Has anybody done tis procedure?
...

https://www.eevblog.com/forum/testgear/old-fluke-multimeters/
In this tread, the original team lead(David R. Taylor, drtaylor) explains the functions of the Sharp µC: dB conversion, Rel conversion etc. - not only a simple display converter.
As an idea for repair, check Q1(proper replacement ideas above); increased R_DS can cause similar symptoms as yours.