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Old 29th Nov 2021, 6:34 pm   #1
Ultrapurple
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Question Suggestions on dismantling Sinclair Microvision?

Hello folks

Newbie to the forum here, so please be gentle with me.

I have acquired a couple of the original (multi-standard) Sinclair Microvision MTV1. Neither is fully operational, which isn't surprising for 1977 budget miniaturisation. I have the service manual (thanks to this forum) and sufficient skills to make a decent stab of repair.

If I can get into them, that is.

Having read the service manual and removed the relevant screws, including those under the label, I can't get the case to slide off the chassis. I can get an uneven gap of around 1 to 2mm around the plastic front and that's my lot.

There's no obvious signs of corrosion (lucky me!) and one of them even has the screen surround entirely intact. I'm loath to use more than moderate force.

Is there a magic trick to opening these that isn't in the service manual? It feels almost as though there's another hidden screw or something but I've definitely removed all of the ones mentioned in that document. The only other thing I can think of is to wonder whether it's necessary to remove (or move) the plastic surround from where I removed the telescopic antenna, but there's nothing obvious.

If my only answer is brute force, is there anything I can do to increase my chances of success? I suspect someone, somewhere has tried freezing the sets, or putting them in an oven, or something... did it do any good?
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Old 29th Nov 2021, 7:59 pm   #2
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Default Re: Suggestions on dismantling Sinclair Microvision?

Hi to all,
Hi Ultrapurple,

Have a look at Frank G's Micro-TV site, Sinclair page.
Google German to English translation:

https://www-guenthoer-de.translate.g...&_x_tr_pto=nui

also the detailed shots section:
https://www-guenthoer-de.translate.g..._x_tr_sch=http

See photo of the entire innards, once open.

Note: You're lucky to have no battery damage. The Ni/Cd (soldered in) rechargeables usually leak & spoil PCB tracks.

Best Regards
jhalphen
Paris/France
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Old 29th Nov 2021, 8:07 pm   #3
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Default Re: Suggestions on dismantling Sinclair Microvision?

Hi to all,
Hi again Ultrapurple,

This is the most complete MTV1 service manual (25 pages) i know of.
It has disassembly instructions.
Hope it helps,

Best Regards
jhalphen
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Old 29th Nov 2021, 8:56 pm   #4
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Default Re: Suggestions on dismantling Sinclair Microvision?

From memory after pulling the telescopic aerial out the black plastic base should prise out fairly easily .
You can then slide the cover off , it can be a tight fit though !
Cheers
Pete
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Old 29th Nov 2021, 10:10 pm   #5
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Default Re: Suggestions on dismantling Sinclair Microvision?

Hi there
I'm working on one at the moment, the only point of force is removing the stubborn telescopic aerial, its plastic surround is very tight, after that and removal of the cab screws as described in the manual it should come easily apart, and yes, the internal batteries in mine have turned to dust long since and damaged some tracks.
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Old 30th Nov 2021, 9:38 am   #6
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Smile Re: Suggestions on dismantling Sinclair Microvision?

Many thanks for all your help - I'm in!!!

The key point was removing the small black plastic surround from where the telescopic antenna plugs in. After doing that, the case slipped off fairly easily. A small amount of force was necessary - it's a relatively tight fit - but nothing like the force I'd applied previously.

I pinged off the sound board to take a first look at the batteries and was quite pleased by what I saw (photo). Work beckons, but I'm beginning the day with a smile.
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Old 30th Nov 2021, 7:47 pm   #7
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Default Re: Suggestions on dismantling Sinclair Microvision?

Might help you .
I’ve found with these the 1uf caps go open circuit causing all sorts of issues
Cheers
Pete
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Old 1st Dec 2021, 3:09 pm   #8
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Default Re: Suggestions on dismantling Sinclair Microvision?

If you aim to get the vhf working, all of these seem to suffer with faulty varicap diodes on the vhf side. I've had other problems on the tuner board with the tuning voltage regulator circuit. I found the only way to fault find on the board was to make up a set of extension leads.
The general build and component quality on these sets is pretty poor.
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Old 1st Dec 2021, 9:36 pm   #9
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Default Re: Suggestions on dismantling Sinclair Microvision?

Thanks to everyone for their help. I've successfully disassembled both sets and am working on getting at least one working.

Both show Ni-Cd damage but pinging the tracks shows they are still conducting.

One set has light chemical damage to the main (power) board. Irritatingly, that's the one with the better PCB (it has screened resist and annotations). Hey ho.

I'm working on gaining a better understanding of the circuits before plunging in with a soldering iron. If I discover anything useful then I will write it up.
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Old 2nd Dec 2021, 10:28 am   #10
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Default Re: Suggestions on dismantling Sinclair Microvision?

I am working on understanding the inner workings of the Microvision. As part of this I've reassembled the full circuit diagram (more or less) into a single image, attached in case it's of use to anyone. It's a work in progress, and I hope to improve on it as time progresses. (Documentation is what I do for a living).
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Old 2nd Dec 2021, 10:32 am   #11
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Default Re: Suggestions on dismantling Sinclair Microvision?

Thanks for posting that, but it's far too small to be of any use.

Could you repost as a .pdf please. That will enable you to upload a bigger file (4Mb).
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Old 2nd Dec 2021, 11:00 am   #12
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Default Re: Suggestions on dismantling Sinclair Microvision?

Sorry - I didn't realise that images got smallerised. Here's a PDF, but note that it has some jpg compression artefacts. It's a work-in-progress so I hope to post a much better version in due course.
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Old 3rd Dec 2021, 12:46 pm   #13
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Default Re: Suggestions on dismantling Sinclair Microvision?

Thanks for the improved circuit diagram. I have another of these horrors waiting to be attended to, and your diagram will help greatly.
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Old 3rd Dec 2021, 1:19 pm   #14
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Default Re: Suggestions on dismantling Sinclair Microvision?

Wait before using it; there is a greatly improved version in progress.
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Old 3rd Dec 2021, 2:57 pm   #15
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Default Re: Suggestions on dismantling Sinclair Microvision?

Herewith the improved version of the Sinclair MTV1 circuit diagram. The PDF has been prepared in a different way and unlike the earlier version has no image compression artefacts.
  • All parts of the circuit are now shown on one sheet
  • Colours are used to delineate various voltage nets (0V, +3V, +5V, -45V)
  • Some parts have been moved around for clarity (eg the batteries)
  • The tube base drawing has been fixed, as have some other tiny original mistakes
  • The rear panel 6V and 12V sockets have been added
  • Labels in red give my best guess on signal names / functions (largely drawn from the existing documentation)

I'm calling this V1.1. It is just about legible when printed on A4 using an inkjet printer, preferably in high resolution mode.

Comments are welcome.

If time permits then I hope to add in some of the missing or illegible component values.

Later, I propose to revise the Service Manual to add this diagram plus a few notes I've found helpful and some workarounds that can be applied to get around some of the Unobtanium issues. Further ideas include adding good photos of the various modules, perhaps indicating adjustment / measurement points. I would appreciate any and all other additional information that could go into the revision.

I stand on the shoulders of giants, to whom I am very grateful.
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Old 7th Dec 2021, 11:30 am   #16
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Default Re: Suggestions on dismantling Sinclair Microvision?

Just to make a progress report: I continue to work on the circuit diagram to make it easier to read, and have also begun work on revising and expanding the Service Manual. I will post the results in due course as a freely-available PDF.
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Old 13th Dec 2021, 12:19 pm   #17
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Thumbs up Re: Suggestions on dismantling Sinclair Microvision?

At last I have a version of the manual I'm reasonably happy with. It runs to 39 pages and contains all of the original material plus a lot of photographs and an improved version of the circuit diagram. I will post it as a new thread rather than burying it here. The file name is

Sinclair Microvision MTV1 Service Manual V2-1 compressed.pdf
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