I'm having two strange issues with my Sharp PT-9000: I can't get a good read from the resistive touchscreen, and the serial port sends and receives garbage data all the time. I have a hunch (more like a wish 
) that these are both somehow power-related problems. Other than that the machine seems fine - though I've only tested the keyboard and serial ports, and not the parallel port yet.
The PT-9000 has up to four daughterboards attached to the mainboard, and judging from the components on it, one of them is involved in all things regarding power regulation - it's loaded with linear regulators and is the only board with electrolytic capacitors on it. It's the board on the lower-right in this photo: https://immich.chuma.org/s/pt-9000/photos/5fab656a-948d-40d3-925b-f328bbd3e065 (50MP image)
This board has nine identical Sanyo electrolytic capacitors on it. None of them appear to have the score marks of a vent-top that I'd normally see on the top of a capacitor, and all of them have a thin layer of whitish residue on the TOP of the caps. None of them appear to be bulging to me.
(There are more photos of this board and others in this photo gallery: https://immich.chuma.org/s/pt-9000)
I'm considering on recapping this board on principal, at it was assembled in late 1993 or early 1994. But I have some nagging questions before I undertake this:
) that these are both somehow power-related problems. Other than that the machine seems fine - though I've only tested the keyboard and serial ports, and not the parallel port yet.The PT-9000 has up to four daughterboards attached to the mainboard, and judging from the components on it, one of them is involved in all things regarding power regulation - it's loaded with linear regulators and is the only board with electrolytic capacitors on it. It's the board on the lower-right in this photo: https://immich.chuma.org/s/pt-9000/photos/5fab656a-948d-40d3-925b-f328bbd3e065 (50MP image)
This board has nine identical Sanyo electrolytic capacitors on it. None of them appear to have the score marks of a vent-top that I'd normally see on the top of a capacitor, and all of them have a thin layer of whitish residue on the TOP of the caps. None of them appear to be bulging to me.
(There are more photos of this board and others in this photo gallery: https://immich.chuma.org/s/pt-9000)
I'm considering on recapping this board on principal, at it was assembled in late 1993 or early 1994. But I have some nagging questions before I undertake this:
- Could the white residue be from the caps failing, or could it have been an indicator that was placed during manufacturing, testing, or assembly?
- I don't own an ESR meter, is it worth getting one just to test these caps? (Probably useful to have around as all of my computers become more and more vintage each day...)
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