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

SiriusHardware · 10th Oct 2021, 1:25 pm

Whew, this is a tough one because we seem to be trying to hit a moving target.

Just to clarify, are you saying you now think this is time related so that if you leave the machine on the video becomes distorted at the top and then eventually goes off?

If I have that right, let it happen so that you have a blank screen and then measure or scope the logic level on IC25 pin 1 and also scope IC17 pins 1, 2, 13 and 12. What waveforms or steady states do you see on those pins when the 'blank screen' fault is present?

10th Oct 2021, 1:25 pm	#259
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,558	Re: Sharp MZ-80K help needed on repair Whew, this is a tough one because we seem to be trying to hit a moving target. Just to clarify, are you saying you now think this is time related so that if you leave the machine on the video becomes distorted at the top and then eventually goes off? If I have that right, let it happen so that you have a blank screen and then measure or scope the logic level on IC25 pin 1 and also scope IC17 pins 1, 2, 13 and 12. What waveforms or steady states do you see on those pins when the 'blank screen' fault is present?