Help: Sharp MZ 700 short fuse with video connection
Posted: Sun Jun 05, 2022 10:33 am
Hello,
I am new to the SHARP community. I have quite a collection of 8-bit computers running. I normally have no big issue repairing them, but now I've encountered an issue I am not sure how to deal with. If anyone can contribute to help me narrowing down the issue I 'd be very grateful.
The story starts here:
I couldn't resist to bid for a SHARP MZ-731 as it was darn cheap, it looked sealed but which as much dirt on it as it was stored in dried-out mud lake for decades. I gave it a shot and got it.
I disassembled it to find the inside of the computer looked fairly alright. Did a lot of case/keys cleaning, a bit retrobrighting and then had a look at the PSU.
I took it out of the machine, looked inside, no signs of any damage incl. capacitors, fuse ok. Then I plugged it in and the voltage ~ 5V looked pretty okay or at least not harmful.
So I dared to put everything back together and turned the Sharp on. The power light comes on and the plotter is making its start-up procedure. I have a winner, so I thought.
My goto video monitors for 8-bit computers are an old Zenith monochrome (for amber nostalgia) and the super versatile Commodore 1084 which never fails my for anything.
As the computer did not come with a video cable and I do not have yet soldered something fitting the DIN RGB connector I figured I will simply switch the video output to B/W with the switch next to cinch plug and use this one. Upon turning on the computer with the monitor connected the fuse in my house went BOOM.
After disconnecting I could say the fuse did its job - nothing was harmed as far as the monitor or other equipment is concerned.
I checked the PSU again, the fuse in the PSU is fine, the voltage is fine and turning the Sharp on still works, power light, Plotter startup etc.
I scratched my head and thought I give it another try with the C=1084 (very stupid, daring, I know). Same result: BOOM. Luckily still everything works.
So okay...fool me once... I will not continue based on my own stupidity. The mistake I am making is probably fairly obvious, but I just cannot figure out why something is shorting nor why it should from connecting a monitor.
The cinch cable I am using is working fine I checked it. It is used for these kinds of connections on other computers with no problem.
Even if I solder the RGB / DIN connector I do not dare connecting it again to anything before I understand what is happening.
Any ideas?
Thank you.
Cheers,
Folko
I am new to the SHARP community. I have quite a collection of 8-bit computers running. I normally have no big issue repairing them, but now I've encountered an issue I am not sure how to deal with. If anyone can contribute to help me narrowing down the issue I 'd be very grateful.
The story starts here:
I couldn't resist to bid for a SHARP MZ-731 as it was darn cheap, it looked sealed but which as much dirt on it as it was stored in dried-out mud lake for decades. I gave it a shot and got it.
I disassembled it to find the inside of the computer looked fairly alright. Did a lot of case/keys cleaning, a bit retrobrighting and then had a look at the PSU.
I took it out of the machine, looked inside, no signs of any damage incl. capacitors, fuse ok. Then I plugged it in and the voltage ~ 5V looked pretty okay or at least not harmful.
So I dared to put everything back together and turned the Sharp on. The power light comes on and the plotter is making its start-up procedure. I have a winner, so I thought.
My goto video monitors for 8-bit computers are an old Zenith monochrome (for amber nostalgia) and the super versatile Commodore 1084 which never fails my for anything.
As the computer did not come with a video cable and I do not have yet soldered something fitting the DIN RGB connector I figured I will simply switch the video output to B/W with the switch next to cinch plug and use this one. Upon turning on the computer with the monitor connected the fuse in my house went BOOM.
After disconnecting I could say the fuse did its job - nothing was harmed as far as the monitor or other equipment is concerned.
I checked the PSU again, the fuse in the PSU is fine, the voltage is fine and turning the Sharp on still works, power light, Plotter startup etc.
I scratched my head and thought I give it another try with the C=1084 (very stupid, daring, I know). Same result: BOOM. Luckily still everything works.
So okay...fool me once... I will not continue based on my own stupidity. The mistake I am making is probably fairly obvious, but I just cannot figure out why something is shorting nor why it should from connecting a monitor.
The cinch cable I am using is working fine I checked it. It is used for these kinds of connections on other computers with no problem.
Even if I solder the RGB / DIN connector I do not dare connecting it again to anything before I understand what is happening.
Any ideas?
Thank you.
Cheers,
Folko