MZ-700 Blank Key.

Doz
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MZ-700 Blank Key.

Post by Doz »

Hi,

About 10 or 12 years ago I bought an MZ-717, with the tape drive, from a car boot. Got it home, plugged it in and it went bang ... Left it on the shelf in my workshop since.

Well, I finally thought I'd fix the thing, I've sorted the power supply out, but I've also got a broken key... The blank one under the break key. What does it do? Searching here and in general hasn't given me any idea!

Anyway, thanks for such a useful forum.
hlide
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Joined: Thu Jan 25, 2018 9:31 pm

Re: MZ-700 Blank Key.

Post by hlide »

it does nothing as I suspect it was specific to Japanese version.
hlide
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Joined: Thu Jan 25, 2018 9:31 pm

Re: MZ-700 Blank Key.

Post by hlide »

Checked, the Japanese version have a Japanese word printed on the key and Western version has no use for that key.
Doz
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Re: MZ-700 Blank Key.

Post by Doz »

Excellent. Thank you.

My next issue is a corrupt character map. It is reacting to the keyboard input. It alters when the system is reset.
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I have found a defective 74S157 multiplexer on the board. Sadly I only have 158's, so I have ordered a replacement. Hope fully this will resolve my issue.
hlide
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Joined: Thu Jan 25, 2018 9:31 pm

Re: MZ-700 Blank Key.

Post by hlide »

So you have first issue with DRAM. Since MONITOR ROM uses system data in DRAM, chance you're not able to go further as long as that issue is not corrected.
psmart
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Re: MZ-700 Blank Key.

Post by psmart »

If you need the blank key, PM me your address I can send you a spare I have and a plunger (assuming the plunger has broken hence missing key). I blew up an MZ-700 2 years ago and have stripped it down for spares.

In terms of the screen, the character generator ROM loses its programming and can cause this issue, I had it on my MZ-80A, same kind of output.Check the CG ROM in an eprom reader if you can. It can be the mux devices but the eprom's were (back in the 80's) only supposed to hold their content for 10 years, quite surprised how may of them are still working today!!
Sharp MZ/X Series Projects and FPGA Emulator
engineers@work : https://eaw.app/sharpmz-series/
hlide
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Joined: Thu Jan 25, 2018 9:31 pm

Re: MZ-700 Blank Key.

Post by hlide »

The 74S157 mux are for DRAM, there is no such mux for CGROM. I just mean DRAM must be fixed to be able to go further. Obviously, it doesn't mean it will fix the CGROM issue.
hlide
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Re: MZ-700 Blank Key.

Post by hlide »

And what @psmart advised is a very simple and good way to check since that CGROM is just plugged (so no desoldering) BUT I wonder which programmer can read it and reprogram it (supposedly using UV erasure is possible), any idea @psmart ?
psmart
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Re: MZ-700 Blank Key.

Post by psmart »

I use an XGecu Pro TL866 II programmer which I find very good, handles most devices. In terms of UV erasure, I no longer have a UV light (I should get one but prefer flash devices these day), what I did for the MZ-80A was to use the CGROM out of the MZ-700 (which survived my stupid 12V mistake) with MSB tied low.

For the OP, if you dont have an eprom reader then best I check to see if I have any blank 2732 devices that I could program up. Will check tomorrow and advise.
EPROM - 1.png
EPROM - 2.png
Sharp MZ/X Series Projects and FPGA Emulator
engineers@work : https://eaw.app/sharpmz-series/
Doz
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Joined: Thu Jun 03, 2021 9:38 pm
Location: Gloucestershire
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Re: MZ-700 Blank Key.

Post by Doz »

@psmart Thanks for the blank key & plunger offer. I'll certainly take you up on that if I can get the thing running.

WRT character ROM, I do have a TL866II, if I need to go that route. I'll have a look to see if I have any 2732's. I Still have my UV box too! Can I just erase and re-programme the existing IC? Is an image available?

Thanks all for the replies.
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