Diagnosing / fixing a TI-59 with no display?

[Pennine_Lad]

Have acquired a TI-59 for a small sum as sold untested, came with Master Library and Navigation module. Wondered what may be failing at present and if fixable, thanks.

All tests with a bench PSU feeding 3.6V to battery terminals and monitoring current draw.

- extensive corrosion of leads from decaying battery vapours, no display
- after cleaning, brief C display on left then zero on right in display, drawing 170 mA
- in this state, numbers pressed were displayed, gave answers to squares, reciprocals but not log and square root
- while still on, display then started giving random numbers, then display failed
- this is current state drawing 130 mA
- the Vgg and Vdd volts as stated in service manual are correct so the on board DC converter board suggests OK with its tantalum caps?

Much of the service diagnostics are with an oscilloscope which do not have.
Is there one or more likely components worth changing out if cheap.

[The four caps for the motor drive card heads need changing and possibly the LM324 op-amp as failed the diagnostics in YouTube video by 'xymox1357' but beleive those won't affect main calculation functions?]

Thanks.
David

[John Garza (3665)]

Any component in the battery well is suspect as the corrosive gasses from decaying batteries are insidious. Worst case, it can affect the logic chips lower in the case. But start with components near the battery.

You mention display problems. Try looking at the two LED driver chips at the top of the battery well SN27882 chips.

-J