Sharp MZ-80A repair

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1024MAK
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Sharp MZ-80A repair

Postby 1024MAK » Sat Nov 14, 2015 12:20 pm

As I showed in the Today I Received topic...
Well here's some more pictures showing my progress :D

image.jpg
Board cleaned after the old caps removed
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Track side cleaned after soldering in the new caps
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Top side showing the new capacitors
image.jpg
Under the hood with the PSU refitted
image.jpg
Powered on okay :-)
image.jpg
Screen close-up, nice and clear :-)
image.jpg
BASIC loaded okay from the tape :-)

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Re: Sharp MZ-80A repair

Postby 1024MAK » Sat Nov 14, 2015 12:26 pm

And so, to the most important test program in the history of the human race...

image.jpg


Now off to download the user manual :mrgreen:

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Re: Sharp MZ-80A repair

Postby jonb » Sat Nov 14, 2015 4:46 pm

Mark... I'm terribly envious. :mrgreen:

Good show on the resurrection! What is that circular component marked BC on the power board?

I was looking round for info about it (specifications really) and the only site I could see is http://www.sharpmz.org/, which is very Web 1.0.

Now see if you can get CP/M on there... seems like the problems are a) only 40 columns and b) only 48k RAM with ROM at the bottom of memory. But there is a way, as you will find out. How will you add proper storage to it? No one wants to load BASIC from tape every time it boots... ;)

Oh yes, what does the keyboard feel like, is it nice and clicky?

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Re: Sharp MZ-80A repair

Postby jonb » Sat Nov 14, 2015 5:04 pm

That's the one off eBay innit?

[Edited to add: Hmm, interesting. Says on here http://www.old-computers.com/museum/computer.asp?st=1&c=172 that it can be overclocked to 4Mhz with a Z80A. Though sadly not how...]

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Re: Sharp MZ-80A repair

Postby 1024MAK » Sat Nov 14, 2015 9:40 pm

jonb wrote:What is that circular component marked BC on the power board?
It's a AC line filter/ common mode choke coil designed for EMI noise filtering applications in conjunction with the two capacitors that I replaced.
jonb then wrote:I was looking round for info about it (specifications really) and the only site I could see is http://www.sharpmz.org/, which is very Web 1.0.
Yes, not that much online about the Sharp computers.
jon and wrote:Oh yes, what does the keyboard feel like, is it nice and clicky?
A bit like that of a Beeb. But maybe a little "softer" with the keys needing slightly less effort.

And yes, it is the MZ-80A off eBay. Been after one for a little while, but they don't come up that often at reasonable prices.

I don't have fixed plans for it yet. As I have to make room for it in the "now far too small" computer room. Boy, what was I thinking, dedicating a small room to this function ](*,). But of course, seven years ago, my interest in computers was not so, erm, extensive :shock:. I had an Atari STFM, a Falcon, a Sinclair Spectrum, one BBC B, two Master 128's, various Psions and some PC's. This forum is the cause. [And maybe some other forums]. So the computer room was designed for, erm eight computers. Don't dare ask how many I now have, I now refuse to count them :lol: .

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Re: Sharp MZ-80A repair

Postby 1024MAK » Sun Nov 15, 2015 6:42 am

This is an interesting site: http://mz-80a.com/

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Re: Sharp MZ-80A repair

Postby jonb » Sun Nov 15, 2015 9:00 am

I saw that yesterday but totally missed the menu bar at the top. Maybe Chrome didn't render it correctly (I'm on the iPad now). Anyway.. That's the only place I've seen manuals for download. It's a pity they are not PDFs. I did come across a few commercial sites that claimed they could send a service manual for a fee; cheeky!

According to one site it is 80 column capable with a mod of some sort (no explanation though!). That's the same place that claimed 4mhz was possible. I'm really looking forward to seeing what you make of it (and waiting for another one to pop up).

Your computer collection history is like mine (except I never had a Falcon, too expensive) and I'm also nearly out of space. I'd struggle to fit a Sharp in there, even on the floor. I need proper shelving!

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Re: Sharp MZ-80A repair

Postby 1024MAK » Sun Nov 15, 2015 10:50 am

I got the service manual from http://www.sharpmz.org/.


The navigation is via the left hand side window via the + buttons. Go to "Downloads" then "Manuals/Data sheets". Direct link :D

But you can also use that sites search box.

I have come across talk of 4MHz operation if you fit a higher speed CPU. I have not seen any details though. I wonder how this would effect the writing to the SRAM that forms the video memory :-k

I don't think the MZ-80A can do proper 80 coloumn as the display system is a fixed hardware system. The only way I can see, is if the monitor ROM was rewritten and the character ROM was changed. Then you may be able to get 4 bit wide (3 bit + a space) characters. Then the software in the ROM would have to flick between the two screen memories to display the two different half screens of 4 bit wide (3 bit + a space) characters. But the compromises would make it horribly limited.

Having seen the 64 character wide screen on the ZX Spectrum (and a similar system on the MTX in a CP/M mode), I will give it a miss.

One further thought about 80 columns, maybe it is a virtual 80 column mode, with only 40 shown on the display, you then use the arrow keys to scroll the screen like a window on a bigger hidden 80 column memory...

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Re: Sharp MZ-80A repair

Postby 1024MAK » Sun Nov 15, 2015 11:01 am

Oh, and some sites talk about a parallel printer port - not on my MZ-80A, and no cut-out for it. The Sharp documents do show one, but on the "slot-in" expansion unit.

The user manual also says that UK machines were supplied as 48k RAM machines as standard, which ties up with there being 24 sharp branded 4116 DRAM chips installed.

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Re: Sharp MZ-80A repair

Postby jonb » Sun Nov 15, 2015 4:22 pm

It's limited... Not even a serial port. :( sort of like a Z80 PET, a.though PETs have user, expansion, IEEE 488 ports.

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Re: Sharp MZ-80A repair

Postby jonb » Sun Nov 15, 2015 5:27 pm

Ha ha, I still want one though.. Pwoooar!

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Re: Sharp MZ-80A repair

Postby kelp » Sat Nov 28, 2015 4:48 pm

Hi folks,

I'm the owner of mz-80a.com :)

jonb wrote:I saw that yesterday but totally missed the menu bar at the top. Maybe Chrome didn't render it correctly (I'm on the iPad now). Anyway.. That's the only place I've seen manuals for download. It's a pity they are not PDFs. I did come across a few commercial sites that claimed they could send a service manual for a fee; cheeky!


That's really weird (and a bit worrying) about the menu bar at the top. I actually test my site only in Chrome and not seen that occur before. It's actually just built in a free Wordpress account with a free theme. Also worrying : I don't want the site to give the impression that there are no PDFs for download. There is actually a little PDF icon just above each book or manual's scanned images. Clicking on that will give you the PDF. If that isn't showing up then...... arrrgh basically :) I'm hoping this doesn't occur very often as it's such a niche site anyway I don't want the occasional visitor to not be able to find the stuff they're after. There isn't much MZ-80A related that isn't on my site, though I am still adding to the site even now.

jonb wrote:According to one site it is 80 column capable with a mod of some sort (no explanation though!). That's the same place that claimed 4mhz was possible. I'm really looking forward to seeing what you make of it (and waiting for another one to pop up).


Yes, there were a couple of hardware mods back in the '80s for the MZ-80A that would give 80 columns (that way C/PM could be run for instance). One was made by Kuma and the other was made by Hippo Associates. I believe the Sharp Users Club got the rights for the Kuma one and started distributing it themselves. You'd be best off asking the SUC if they still have any or at least any schematics perhaps.

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Re: Sharp MZ-80A repair

Postby kelp » Sat Nov 28, 2015 4:53 pm

1024MAK wrote:I have come across talk of 4MHz operation if you fit a higher speed CPU. I have not seen any details though. I wonder how this would effect the writing to the SRAM that forms the video memory :-k


I've never actually seen it in operation but do think it was an easy mod to make, I can get some information from my (almost) complete collection of Sharp Users Club magazines if you'd like. One thing I know, the 80A will never load any software from tape again if you up the speed to 4Mhz.

1024MAK wrote:I don't think the MZ-80A can do proper 80 coloumn as the display system is a fixed hardware system. The only way I can see, is if the monitor ROM was rewritten and the character ROM was changed. Then you may be able to get 4 bit wide (3 bit + a space) characters. Then the software in the ROM would have to flick between the two screen memories to display the two different half screens of 4 bit wide (3 bit + a space) characters. But the compromises would make it horribly limited.


I also have never seen the 80 character mod in action but I believe you are correct that the Monitor ROM (kernel) was essentially replaced. The 80 columns were indeed achieved with use of the 80A's 2K of screen RAM and 80 columns were, indeed, shown on the single screen.

Cheers :)

P.S. Small thing : You only need to type 'L' (not 'LOAD') in the Monitor to load a M/C program from tape ;)
Kelp

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Re: Sharp MZ-80A repair

Postby 1024MAK » Sat Nov 28, 2015 10:05 pm

Well, if it helps, I have no problems surfing mz-80a.com :)

I use Firefox on a Linux system.

Today, I used an iPad mini to have a look. You have to press an on screen button to get to the menu on this size screen:-
image.jpg
See it there in the top left corner, the blue square with white horizontal lines, just above the picture of a MZ-80A computer in a circle.

Thank you for building this web site =D> =D> =D>

It certainly adds more information about the Sharp MZ-80 computers online. Which is much appreciated, given that there are not many web sites for these machines.

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Re: Sharp MZ-80A repair

Postby 1024MAK » Sat Nov 28, 2015 10:22 pm

kelp wrote:P.S. Small thing : You only need to type 'L' (not 'LOAD') in the Monitor to load a M/C program from tape ;)
Kelp
Yeah, I did read that, but force of habit caused me to get a bit carried away :lol:

I do the same on machines where ? can be used in place of PRINT... :roll: By the time I remember, I have already typed "PRINT" #-o

I have since found some further information on both increasing the CPU speed (where they do say that it kills the tape loading and saving) and a little bit of info on the 80 character display. I will go back and study these modifications, but I am not sure I will actually modify my MZ-80A.

I currently have too many other projects and jobs to do.

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Re: Sharp MZ-80A repair

Postby kelp » Sun Nov 29, 2015 11:11 am

1024MAK wrote:Thank you for building this web site =D> =D> =D>

It certainly adds more information about the Sharp MZ-80 computers online. Which is much appreciated, given that there are not many web sites for these machines.

Mark


Oh, no problem at all, thanks very much, I'm glad it's useful. That was mainly the impetus behind building the site, I didn't feel there was enough information out there about my machine. I would say it and obviously the beeb I had were my favourite machines when I was growing up. It was hard getting software for the 80A back then though and I don't think we were aware, as a family, of the Sharp Users Club at the time or the Sharpsoft software company with its user notes (full of contributions from the userbase). I think I'm the only site with those books and a collection of Sharpsoft notes out there. I do have all the SUC magazines but felt there was no point adding them to the site as they are all already available at the SUC website. Another difference between my site and the others out there seems to be that my PDFs are all searchable (even the Owner's manual).

The sharpmz.org site is also an excellent resource but I wanted my site to be more games and programming oriented (a bit like a catalogue of games in the mould of, say, lemon64), whereas sharpmz.org is full of more technical info. So hopefully mine is good in addition to that one.

Hey, if you ever want any software for the machine I'm willing to send out tapes...............

kelp

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Re: Sharp MZ-80A repair

Postby jonb » Mon Jan 04, 2016 5:12 pm

@kelp: I have one now! :)

So I will no doubt be asking all sorts of questions...

Cheers
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Re: Sharp MZ-80A repair

Postby Fwapp » Tue Mar 01, 2016 7:50 pm

Looking nice and tidy :)

I've an MZ80A that came to me dead - the paper mains caps had blown themselves to peices so I took the opportunity to completely recap the PSU as I was in there.

The switch mode PSU whines a bit, but the machine powers up fine. Only trouble is the tape I have won't load :(
Acorn Atom (iss.4[WIP]) AtoMMC V2.0, BBC B (iss.7) Sir Morris SD Card and MMFS 1.27, Acorn Electron (iss.4), A3000

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Re: Sharp MZ-80A repair

Postby kelp » Fri Apr 22, 2016 2:31 pm

jonb wrote:@kelp: I have one now! :)

So I will no doubt be asking all sorts of questions...

Cheers
JonB


Ah, sorry had forgotten to check this thread. Good to hear more MZ-80As are floating about still :)

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Re: Sharp MZ-80A repair

Postby kelp » Fri Apr 22, 2016 2:33 pm

Fwapp wrote:The switch mode PSU whines a bit, but the machine powers up fine. Only trouble is the tape I have won't load :(


I can send tapes of software if anyone wants any (you may have to supply the tape as I don't have many at the moment)... really great to read about more people with MZ-80As, hope to have some homebrew ready as well sometime this year

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Re: Sharp MZ-80A repair

Postby kelp » Fri Apr 22, 2016 2:36 pm

jonb wrote:@kelp: I have one now! :)

So I will no doubt be asking all sorts of questions...

Cheers
JonB


JonB. For some reason I didn't have any notification of your PM to me ! So only just seen it ! Apologies about that. I don't seem to be able to reply or contact you on here either, (maybe I've not posted enough). I'll try again later anyway.

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Re: Sharp MZ-80A repair

Postby 1024MAK » Fri Apr 22, 2016 2:38 pm

No, sending / replying to PM's is not available until you have a lot more posts, unless you contact an admin and ask for PM's to be enabled.

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Re: Sharp MZ-80A repair

Postby kelp » Sat Apr 23, 2016 10:12 am

1024MAK wrote:No, sending / replying to PM's is not available until you have a lot more posts, unless you contact an admin and ask for PM's to be enabled.

Mark


All sorted now, thanks :)

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Re: Sharp MZ-80A repair

Postby kelp » Thu Oct 27, 2016 8:07 pm

Hey folks,

I have a 2nd MZ-80A now but it doesn't switch on. I'm not remotely hardware/electronics savvy but took a quick look at it tonight, the capacitors don't look like they're bulging. A quick check of the two 1.6A fuses and one had a clear break in it. Replaced that tonight but although there is a slight bit more life (you can hear the speaker/beeper initialise in the same way my working MZ does) little else happens. When you turn the machine off the VDU seems to briefly show a green line which disappears (again sort of in the same way that my working MZ does). Also, I tried turning it on again but noticed a horrible acrid smell (no smoke though). Hmm, anyone any ideas what could be wrong? Would I perhaps need to replace the entire PSU?

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Re: Sharp MZ-80A repair

Postby 1024MAK » Thu Oct 27, 2016 10:59 pm

The acrid smell is likely to be one of the mains filter capacitors degrading.

It sounds like something has failed, hence why one of the fuses was blown.

If you remind me, I will post more info next week.

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Re: Sharp MZ-80A repair

Postby kelp » Fri Oct 28, 2016 9:39 am

Ah thanks Mark, I'll do a little reminder next week, any info will be most helpful indeed.

Cheers
Ben

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Re: Sharp MZ-80A repair

Postby kelp » Thu Nov 03, 2016 7:57 am

Just a little reminder :) Honestly, if you have any further info then it would be massively appreciated.

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Re: Sharp MZ-80A repair

Postby 1024MAK » Fri Dec 02, 2016 2:39 am

Whoops, I missed your reminder :oops:

Do you have a multimeter?

The details of the repair on mine started in this thread.

Also have a read of Jon's thread about his. He needed help locating the X2 capacitors that needed replacing. Link here :wink:

Once the two mains voltage X2 capacitors (C101 and C102, see pictures at the top of this thread) have been renewed, it's time to investigate the main power supply board.

Mark
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Re: Sharp MZ-80A repair

Postby kelp » Wed May 03, 2017 9:50 am

Hi sorry for the delay as well. Thanks for taking the time to reply. Yes, as expected, it's probably a little above my skill level. I'm not much of a hardware / electronics person. I don't have a multimeter. I'm thinking I'll have to find someone that still services old electronics and see if they can carry out the work. Really appreciate your time/effort though, thanks!

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Re: Sharp MZ-80A repair

Postby 1024MAK » Wed May 03, 2017 5:10 pm

If you are in the U.K., Ian at www.mutant-caterpillar.co.uk may be able to help. He offers a proper repair service for many retro computers.

Mark
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