Fluke 8050A decimal point problem

[mellowamoya]

Hi All,
Im hoping someone can help with this my trusty Fluke8050A that has been on the bench for many years and worked very hard, it has developed a problem, it still works and reads but all the decimal points on the display are on all the time no matter what button is pressed, sometimes the last one on the right will be flashing but most of the time they are just all on.
any pointers as to fault find the problem would be great.
thanks
dennis

[retiredcaps]

8050A Service manual at

http://bama.edebris.com/download/fluke/8050a/8050a.pdf

suggest for (from table 4-13 troubleshooting guide)

All or no decimal points that U16, U17, interconnect may be at fault.

[JFJ]

The decimal points are driven by U16 - a four segment LCD driver (CD4054BE). Hopefully, replacing that IC will cure the fault. If not, then it may be game-over, because the decimal point control signal comes directly from pin 22 of U17 (Fluke's own 40 pin controller).

If your meter is the 8050A-01 (rechargeable battery option) then the display will have a 'BT' (low battery) indicator, which is also controlled from pin 22 of U17. So, if 'BT' isn't permanently on, then U17 is unlikely to be faulty.

Sorry, it's the 'REL' indicator that is "also controlled from pin 22 of U17" (I misread 'Out 4' as pin 4 on the CD4054B datasheet). So, if 'REL' isn't permanently on, then U17 is unlikely to be faulty.

[ModemHead]

Before heating up the soldering iron, disassemble the ribbon cable interconnect and give it a clean, just in case.