MZ80A in need of repair - SE England

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joolz2021
Posts: 2
Joined: Mon Oct 11, 2021 9:47 am

MZ80A in need of repair - SE England

Post by joolz2021 »

Hi

I've just powered on my MZ80A after a few years and the screen is now jumping around erractically, before closing down to a line in the middle. Also, the tape player has stopped working. I'm not electronivally savvy so does anyone know of someone who repairs vintage computers in the south east England location. I'd love to get her back in working order.

Many thanks
Chris
psmart
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Location: Leeds
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Re: MZ80A in need of repair - SE England

Post by psmart »

Hi Chris and welcome,

Age has taken out the capacitors, the monitor section gets hot and the capacitor decay rate is that much greater than the rest of the machine.

As a minimum the time base capacitor (C2007) for the vertical line driver IC UPC1031H goes u/s and as a consequence can take out the IC. I replaced the IC on one monitor due to the exact same symptoms your seeing only to find it didn't work properly and analysis showed it was the time base capacitor. Since then I replace all capacitors on the monitor (Ive repaired/renovated a few MZ-80A's. 80B, 2000's) as standard. The IC UPC1031H is not really available now, you can though easily pick up the UPC1031H-2 which has a shorter heatsink tab so an adaptation needs to be made to fit the original heatsink. Also the sound may not work due to capacitor C2049/2053 going u/s so a full recap on the monitor mainboard has multiple plus sides. The capacitors have to be high quality, I've tended to use RS PRO components but on one occasion I used some cheap Chinese caps on the horizontal deflection circuit as I'd run out of RS parts and I've ended up with some weird screen effects! Also the 10uF/25V bipolar ballast capacitor is best not to replace, there is no data sheet and modern parts, even 50V Nichicon parts (the top end of capacitors), are a fraction of the size and no doubt the ripple/ESR compared to original are much higher as the new parts get hot and pop!!!! I've kept the old part after testing but will soon venture into trying a Polyester equivalent which has low ESR/ripple.

The tape player, the belts harden and warp (or on the MZ-2000's they turn to black tar goo along with the pinch roller), so at a minimum the belt will need replacing and the speed set using a calibration tape.

Any real electronics repair shop (not board swappers) should be able to fix the two problems especially as the service manual is online at https://original.sharpmz.org/mz-80a/download/80asm.pdf - budget depending, ask for a full recap of the monitor mainboard. Just google your local area as the machine is really too fragile and heavy to be shipping to/fro.

Great machines, I've made a few upgrades for them for better use-ability which are on my website, but they are iconic and just so cool to have on the desktop and tinker with (imho)!

Greetings to the south (Brighton?)!!
Sharp MZ/X Series Projects and FPGA Emulator
engineers@work : https://eaw.app/sharpmz-series/
joolz2021
Posts: 2
Joined: Mon Oct 11, 2021 9:47 am

Re: MZ80A in need of repair - SE England

Post by joolz2021 »

Many thanks for all the information - it is really helpful!

I will certainly look for a decent repair shop- am in fact moving to Lincolnshire so will have a look after I move (if anyone has any recommendations, do let me know).

This machine was my first computer and I agree - I love the look of them and doing a bit of old school programming on them.

Kind regards
Chris
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mz-80a
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Joined: Thu Jan 25, 2018 10:46 am
Location: Devon, UK
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Re: MZ80A in need of repair - SE England

Post by mz-80a »

Quite clearly, they are the best MZ :D
MZ-80A Secrets
https://mz-80a.com/

Sharpworks (Sharp MZ homebrew)
http://mz-sharpworks.co.uk/
charminator
Posts: 11
Joined: Tue Apr 17, 2018 8:38 am
Location: Germany, Hamburg

Re: MZ80A in need of repair - SE England

Post by charminator »

... where do i get these calibration tapes and how can i calibrate the speed ?
Collecting -K- since 1978

Supporter of Karl Heinz Maus famous MZ site ;)
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