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

Timbucus · 4th Sep 2021, 1:52 pm

Indeed - the probe would allow you to see if the pulses are present on the scanning lines I suggest - even though you can't see the frequency you can work out what they have on them - so start with Pin 6,7 and 8 of the CG-ROM (In the area around IC39-IC43) they should all be pulsing at slightly different frequencies as the characters are generated.

Next see if A0-A9 on IC42 or IC41 which are Pins 5,6,7,4,3,2,1,17,16 and 15 are also pulsing - that shows that the RAM is being read out...

Finally back to the CG-ROM and give the binary value of D0-D7 9,10,11,13,14,15,16 and 17 - if they are pulsing then that is also a result.

You might be able to judge the speed of pulsing on the RAM A0 should be pulsing fastest and A9 slowest but, that is a guess it could be the other way around as I do not know the RAM layout.

4th Sep 2021, 1:52 pm	#6
Timbucus Octode Join Date: Mar 2019 Location: Barry, Vale of Glamorgan, Wales, UK. Posts: 1,364	Re: Sharp MZ-80K help needed on repair Indeed - the probe would allow you to see if the pulses are present on the scanning lines I suggest - even though you can't see the frequency you can work out what they have on them - so start with Pin 6,7 and 8 of the CG-ROM (In the area around IC39-IC43) they should all be pulsing at slightly different frequencies as the characters are generated. Next see if A0-A9 on IC42 or IC41 which are Pins 5,6,7,4,3,2,1,17,16 and 15 are also pulsing - that shows that the RAM is being read out... Finally back to the CG-ROM and give the binary value of D0-D7 9,10,11,13,14,15,16 and 17 - if they are pulsing then that is also a result. You might be able to judge the speed of pulsing on the RAM A0 should be pulsing fastest and A9 slowest but, that is a guess it could be the other way around as I do not know the RAM layout.