UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Sharp MZ-80K help needed on repair

SiriusHardware · 10th Oct 2021, 6:53 pm

While it's in that condition use your little resistor rig to connect the disconnected 8255 pin 14 to nearby +5V (via the resistor). Now what voltage do you see on the 8255 pin, still 0V or some other voltage, with the resistor connected?

If you see 5V with the resistor connected leave the resistor in place and keep checking the 8255 pin voltage to see if it stays at +5V. If you see 0V on the 8255 pin even with a pullup resistor connected, report back.

10th Oct 2021, 6:53 pm	#266
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,577	Re: Sharp MZ-80K help needed on repair While it's in that condition use your little resistor rig to connect the disconnected 8255 pin 14 to nearby +5V (via the resistor). Now what voltage do you see on the 8255 pin, still 0V or some other voltage, with the resistor connected? If you see 5V with the resistor connected leave the resistor in place and keep checking the 8255 pin voltage to see if it stays at +5V. If you see 0V on the 8255 pin even with a pullup resistor connected, report back.