MZ-700 Blank Key.

Doz
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Re: MZ-700 Blank Key.

Post by Doz »

Hold that thought... scoped up the 5V around the board... there was a lot of crap on the rail around the MB8264-15 memory IC's... changed C82 and C86 ....
IMG_20210704_211401.jpg
Bingo... I'm going to change the rest of those electrolytics, and there's a tant there too, and my hatred of tants goes back to the 70's...
psmart
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Re: MZ-700 Blank Key.

Post by psmart »

Cool :) - well done.

One of the first things I do is check the voltage as some of the MZ-700's have been down to 4.69V, a tweak of the var-resistor in the PSU sorts it out. The tantalums of the era are known for going short circuit and the electrolytics drying out, cool analysis.

I re-capped an X68K and an MZ-2500 last week, 100's of elecs and tants, what a job and the X68K is a real pain, multilayer PCB with large power planes and no thermal pad grading!
Sharp MZ/X Series Projects and FPGA Emulator
engineers@work : https://eaw.app/sharpmz-series/
Doz
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Re: MZ-700 Blank Key.

Post by Doz »

The luxman amp I mentioned a few weeks ago had many ... https://andydoz.blogspot.com/2021/07/lu ... ation.html

Must go and see if I have a better TV/monitor somewhere ... I'd rather like to take you up on your earlier offer of a "blank" key & stump if the offer still stands.
Doz
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Re: MZ-700 Blank Key.

Post by Doz »

Most of the RF output transistors I do as a day job have zero thermal relief on the pads, as the tab of the transistor is soldered to a large copper land in lieu of a heatsink. Hit it hard and fast with a metcal and a darn big bit usually results in them coming out without wrecking the board. *usually* ....
psmart
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Re: MZ-700 Blank Key.

Post by psmart »

Very nice, sometimes we rush into 'new tech' we forget what gems existed, but the price of the caps, 50pounds!!!

Yep, just PM me when you want it sending.

The X68K I tried multiple tips until I found a balance, not too fine or thick, 400'c, nip the tantalums off, wet it with fresh solder and solder suck - pulled a land off on the first few tries but once I got the method it worked reasonably well.
Sharp MZ/X Series Projects and FPGA Emulator
engineers@work : https://eaw.app/sharpmz-series/
psmart
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Re: MZ-700 Blank Key.

Post by psmart »

Looking through your blog, an impressive set of machines has passed your way. I suddenly hit on the RG-3915 and it got me thinking, do you have sources for spare cogs? Reason is I'm building my collection and have an MZ-2000 and MZ-2500 both using the exact same cassette mechanism. A triple solenoid 4 belt mechanism with a flying cog rotating between the reels depending on mode. Both had pinch roller issues where it turned to sludge, managed to get new ones from aliexpress but the actual cogs are cracking on both of them, so play/ff/rew are random as friction comes and goes. I was considering getting them scanned and printed, currently searching for a company to do this, just wondered if there was a company/person doing this kind of thing?
Sharp MZ/X Series Projects and FPGA Emulator
engineers@work : https://eaw.app/sharpmz-series/
Doz
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Re: MZ-700 Blank Key.

Post by Doz »

I'm sorry, I don't ...

OK, got all the 8 caps replaced, repaired the keyboard connector (all the keys work, no one is more surprised than I) , changed the belt and the take-up reel table rubber to get the cassette deck to operate, and I'm now a shade stuck. A while back (and I forget where I got it from) I downloaded a wav of "Z80 BASIC V1.0" , which my friend nathan stuck on a tape for me.

I type L and CR... and hit play , everything seems good, but nothing changes on screen ... should it display "found xxxx" or something?
Doz
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Re: MZ-700 Blank Key.

Post by Doz »

Hold the press ... I was too hasty ... I'd never got the "press play" thing before ... now I'm getting there !
IMG_20210708_222133 (1).jpg
psmart
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Re: MZ-700 Blank Key.

Post by psmart »

No problem, I located a company in Leeds who can scan and print, hoping to get it sorted next week.

Was just about to post the text below but probably not relevant now, great news, all working :)

The MZ700 cassette decks that have passed my way, especially if I've changed the drive belt, need calibrating with a 4KHz alignment cassette. The odd deck has needed azimuth setting too, this manual, page 17 https://original.sharpmz.org/mz-700/download/sm700.pdf details the procedure. It suggests using 8KHz for the tape speed and 3KHz for the azimuth, my alignment tape only has 4KHz so have managed with that.

Also, your friends tape drive, if not setup recently can be an issue too. I have quite a few tapes which came with a machine but not readable on an adjusted deck! One suggestion, albeit needs patience, set the tape speed and if it doesn't load, tweak the variable resistor a bit till you find a position it reads the cassette! You could setup your drive, borrow his cassette drive, load up S-BASIC on his drive, swap decks and run the tape copy procedure at 0x1108 so you get a good master.

When you type L, it should, within a few seconds output 'Loading XXXX'.
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
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Re: MZ-700 Blank Key.

Post by Doz »

He recorded it on a Nakamichi Dragon I set up and calibrated for him a couple of years ago, it should be good ;)

I can't get any further, and I'm going to hit the hay. I'll get out the cal tapes at some time and set the deck up.

If your guy is leeds lets you down, give me a shout, there's a very talented 3D printing guru I know in Gloucester.
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