Mz700 repair project

CRG
Posts: 21
Joined: Tue Feb 05, 2019 10:11 am

Re: Mz700 repair project

Post by CRG » Fri Mar 01, 2019 11:11 am

Jo Even wrote:
Fri Mar 01, 2019 8:43 am
You must also disconnect the datarecorder's read/write signal from the 8255 when doing this. Instead of modifying the motherboard you could make a short cable between the motherboard and datarecorder, and do the switching there.
Good idea.

But I've hit another road block. I tried a jumper cable last night with no luck so I thought I'd remove the board for a closer look at what is doing on. There is corrosion on the bottom of the board around the read port and there is a short between the read input and ground which obvious isn't correct so that needs address but its not the main issue.

To remove the board I obviously had to remove the keyboard again but my problems with the keyboard connector on the board continued (if you watched the 2nd video you'll understand) and this time as well as pulling out some pins again its cracked the connector on the board and the bent pins have damaged the ribbon. Safe to say it nearly went out the window at this point. I've been over the keyboard connector in detail and I don't see any way it comes apart to release the ribbon so I can only assume the issue is from the previous owner. I think at this stage it will be easier to replace the ribbon and motherboard connector with pins and wires as to be honest I could possibly save the ribbon but the connector is a lost cause.

Jo Even
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Re: Mz700 repair project

Post by Jo Even » Tue Mar 05, 2019 2:57 pm

CRG wrote:
Fri Mar 01, 2019 11:11 am
To remove the board I obviously had to remove the keyboard again but my problems with the keyboard connector on the board continued (if you watched the 2nd video you'll understand) and this time as well as pulling out some pins again its cracked the connector on the board and the bent pins have damaged the ribbon.
Yes, the ribbon and connector is a POS... But atleast it's detachable, if you've ever repaired a Spectravideo you'll know that this isn't always the case. The first thing I did when fixing up a Spectravideo Xpress was to remove the stiff, soldered-in keyboard cable and replace it with pin headers and flat cable. It may take a little while but it's worth it.

Btw both the arrow- and letter-keycaps has now been modelled and printed. Just need to print the bit that attaches to the plunger, hope to do that tonight so I can post some pictures.

Jo Even
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Re: Mz700 repair project

Post by Jo Even » Tue Mar 05, 2019 6:32 pm

MZ700 new keys.png
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PM me your address and I'll send you your new keys :)

I can't remember which of the arrow keys you needed, but don't worry if it's not arrow right, they are all identical.

CRG
Posts: 21
Joined: Tue Feb 05, 2019 10:11 am

Re: Mz700 repair project

Post by CRG » Thu Mar 07, 2019 1:31 pm

An absolute gent my good sir. I've replied to your e-mail as I haven't been around much the last couple of days.

I've ordered 2 10 pin (couldn't find 20 pin) XH right angle connectors with a pre-wired 20cm lead from each. Might be a week before I get them but we'll get this old machine working sooner or later.

CRG
Posts: 21
Joined: Tue Feb 05, 2019 10:11 am

Re: Mz700 repair project

Post by CRG » Mon Mar 18, 2019 12:25 pm

I spent some time over the weekend and got the power supply finished (fitted with new filter caps), cleaned up the underside of the board and removed the short on the read jack, repaired the keyboard again (replaced the ribbon with xh type connectors but not without problems) and reassembled with a bit of a clean.

I need to give massive thanks to Jo Even who very kindly helped me with this project by 3D printing the 2 keys I was missing. He also very kindly surprised me with a tape of Basic.

So to finish of I ran basic and a game I managed to grab of eBay, Le Mans Turbo.

You can check out the video of it here - https://youtu.be/ikc4UlYnyKs

Its a long video at 55 minutes but there is a lot to get through.

I will get to retro brightening at some point but the weather here in Northern Ireland has been awlful of late so it will have to wait.

I do have another idea up my sleeve for a wee mod but I need to order something first.

Anyway just thanks again to Jo Even for all his help to date. If you get a chance check out the youtube videos and I always welcome feedback.

hlide
Posts: 215
Joined: Thu Jan 25, 2018 9:31 pm

Re: Mz700 repair project

Post by hlide » Tue Mar 19, 2019 7:38 pm

I tried to retrobright some MZ-700 keys without UV using only H2O2 and heat through a sous-vide cooker (not sure how to call that machine).
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But I got a better result with TO8 keys as I could refine the experiment.
Before:
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After:
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Jo Even
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Re: Mz700 repair project

Post by Jo Even » Tue Mar 19, 2019 9:02 pm

Good work, another MZ brought back to life. Careful with retrobrighting it, looks like the key lettering fades just as quickly as the yellowing on the MZ-700.

hlide
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Re: Mz700 repair project

Post by hlide » Tue Mar 19, 2019 9:45 pm

The lettering is not fading but I have doubt about color : unlike TO8 keys the color keys on MZ-700 appear to be sensitive where there is a yellowish taint. The part where there is no yellowish taint has no changes. The lettering looks better indeed.

Jo Even
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Re: Mz700 repair project

Post by Jo Even » Tue Mar 19, 2019 11:15 pm

I have seen several retrobrighted 700's where the lettering is almost gone.

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mz-80a
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Re: Mz700 repair project

Post by mz-80a » Wed Mar 20, 2019 10:20 am

I'm not sure I see the point anyway unless you are intending on displaying your machine somewhere for people to see plus it won't last anyway.
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