Sharp MZ

Hi I found a large A3 scan of the MZ-80A floppy disk card, this will work in the B if you dissable the CS/CE to the EPROM IC 3 PIN 8 to IC 5 PIN 1. add pull-up resister to IC 5 PIN 1

I was correct there is one track that has to be cut to convert the A card to a B card the EPROM's CS/CE signal IC 3 PIN 8 to IC 5 PIN 1
IC 5 PIN 1 will need a pull-up resistor adding. see images

Hi the Sharp Users Club had died 1980-2020 due to lack of members, Last SUC magazine 2020 vol2 November issue is still at the printers (lockdown problems) I have a large selection of tape and disks for various Sharp machines. I have an 800 basic disk marked PIXEL (EPSON) but can not access it, as al...

Do you want to run CP\M or do you want to extract data from the disks? I have a KroFlux and can read the disks except the boot sector, but I know what it is anyway. And I have my own software that can mount the KroFlux file and display directories and extract files. The Mz-80A FD card will work in t...

I had a similar fault on a MZ80K. I was the flash timer is not working. The K used a 555 timer and the MZ80A uses a 556 (IC51)+ caps C39,C40 On the A the start up order is the setup clear screen print ** MONITOR SA-1510 ** test for he USER ROM/RAM at $E800 (IC43 next to the Monitor ROM) print Newlin...

Note: just to make things more interesting The MZ-80K and MZ80A ROM and RAM opcode timings are the same. But the MZ700 runs opcodes faster in RAM than ROM as the LSI chip controls the /WAIT ine of the CPU and it adds 1 extra T-cycle to the opcodes in ROM. This speeds up the tape read/write routines ...

Sounds like the horizontal synch has failed.
Check test points 13 to 21 on the video board with an oscilloscope, ( see page 40 of the MZ80K Service Manual) and compare with traces on pages 19/20.

Check that capacitors C407 c406 c503 or c504 are OK. I can remember repairing a K power supply (that kept blowing fuses ) for MH in Weymouth many years ago by replacing the blue capacitors which are part of the voltage setting circuit. I think one was short circuited but we replaced all 4. ESR is sh...

Hi I have a MZ80K with the same problem. A static random screen, the pattern is always the same on power or reset. I reproduced the fault on another MZ80K by testing a RAM checker eprom that it did not work in the faulty machine. The both MZ80K could not see the eprom,the eprom was too slow 350ns. a...

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