UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Reply
 
Thread Tools
Old 16th May 2019, 10:32 am   #1
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,511
Default Sinclair Microvision from the NVCF

I spotted this on the BVWS stall at the NVCF, its an MTV1B which is the UK version of the second series Microvision. It looked a bit sad, with dried-on sticky tape marks and holes drilled in the cabinet, but I’ve not seen one for ages so I thought I’d give it a go. This model was introduced in 1978 and at the time was the smallest TV set you could buy in the UK. It runs from four ‘AA’ sized cells and has a 2” electrostatically deflected picture tube. It was really quite an achievement; remember the first Sony Watchman was still five years at this stage.

At home I tried the set and it didn’t work. Thinking about that, I stripped the cabinet away and sprayed it in label remover. After that a long soak in hot soapy water removed the worst of the tape marks. I filled the holes in the cabinet by first covering them with electrical tape on the outside and then back filling them from the inside with epoxy resin (rapid type). Heating this gently with a hair dryer while it cures makes it less viscous, so it runs better into the features of the void it has to fill. Once the resin was hard, the tape was removed and the surface touched in with black paint. Its not perfect, but it looks pretty good.

Back to the tiny chassis. Applying 6V across the battery snap showed no current drain so I checked the switch – open circuit. Shorting it out made the screen light up instantly (the tube is directly heated) so I scraped the contacts clean and tried again, this time it worked. There were a few issues to attend to to deal with the effects of battery leakage in the past and a bit of suspect soldering, but after that a picture could be tuned in. There was also sound but it wasn’t very good.

If you are used to normal sets then the Microvision can be a bit baffling. A lot of it is built on three purpose designed ICs – they are not replaceable so if you damage one you can’t repair the set. A fourth IC does the intercarrier sound, that is a standard part from Hitachi. The tuner is also special, it uses a negative tuning voltage for its variactor diodes and is largely hand made – something else to be careful with. The electrostatically deflected tube means that there are high voltages everywhere, sometimes where you’ve least expect. The line and frame shift controls for example have a cool 2kV on them, and any flashovers are likely to ruin the ICs. Some of the holes I filled allowed access to these controls, so the set wasn’t really safe like it was.

I found a circuit diagram for the set but it was a different issue to mine and differed in some details. The scan was also hard to read, but it gave the general idea. The various preset controls are not marked and with such a strange set it seemed a good idea to work out what each one does and see which was not having the desired effect. A combination of clues on the diagram and in the set allowed me to work it all out, looking from the front and working back the functions are:

Right Hand Side (under the tube):

front: height
front middle: focus*
rear middle: frame shift*
rear: line shift*

Centre:

front: width
middle: set -45V
rear: contrast

Left Hand Side (behind the tuning control)

front: preset line hold
front middle: user line hold
rear middle: user frame hold
rear: AGC

Controls marked * are at a high potential and must only be adjusted with a non-metallic insulated tool – I used a ceramic screwdriver.

I started with the set -45V control. With exactly 6V at the battery snap I set this for -45V on the wiper of the control itself, the diagram shows that this is tied to the -45V rail. I did it with the set tuned in to show a normal picture and the sound muted.

The AGC should be set to give a ‘clean’ picture from a strong signal (modulator output loosely coupled to the rod antenna etc). Some settings will give line pulling at the top of the picture so look carefully. The contrast control (internal preset, there is no user contrast control) also does some odd things so needs to be adjusted carefully. Because of the short length of the tube the focus is a compromise setting but it should be possible to get it pretty good – I could easily read the programme guide from the Freeview receiver with it set up optimally. The is no brightness control so with everything else about right the picture will still look a bit bright and grey – that just seems to be the way these sets are.

After all that the results looked pretty good. With the sound at a moderate level the current consumption is about 120mA with a battery end voltage of about 1V per cell. This suggests that good battery life is possible if alkaline cells are used. The tuning does drift as the battery voltage falls however, part of the circuit economy is that the tuning voltage isn’t accurately stabilised.

There are a few things left to do. Firstly, the little screw terminals for an external antenna are missing, as is the spring contact inside for the rod antenna. Can anyone who has one of these sets photograph these parts for me so that I can make new ones? Also, the stickers underneath are missing – again if you have one of these sets could you scan the bottom in for me (it would come out best it if the flexible prop stand was first removed).

I have the first Watchman too (FD-210BE), this came from the NVCF years ago and had a duff converter transformer which I rewound. See:

www.walkmancentral.com/products/fd-210be

It gives a brighter and more contrasty picture than the Sinclair but the latter is still an impressive piece of work, especially given the era in which it was designed and the tight budgets that were available to do it.
Attached Thumbnails
Click image for larger version

Name:	MTV1B 1.jpg
Views:	298
Size:	94.6 KB
ID:	183204   Click image for larger version

Name:	MTV1B 2.jpg
Views:	265
Size:	84.7 KB
ID:	183205   Click image for larger version

Name:	MTV1B 3.jpg
Views:	265
Size:	86.5 KB
ID:	183206  
Attached Files
File Type: pdf MTV1B diagram.pdf (634.6 KB, 55 views)
Studio263 is offline   Reply With Quote
Old 16th May 2019, 10:45 am   #2
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 3,004
Default Re: Sinclair Microvision from the NVCF

Thanks for posting this detailed info - I have one which I've owned for for a very long time, although not from new. It's still in its 'leatherette' case, no doubt one reason why the set itself is in nice, unmodified condition.

When I dusted off the (previously working) set to give it a last run out just before the analogue switch-off I found it to be in a bad way due to dried-out capacitors which were duly replaced, so I had it running for a whole evening shortly before the switch-off.
SiriusHardware is offline   Reply With Quote
Old 16th May 2019, 12:01 pm   #3
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 6,898
Default Re: Sinclair Microvision from the NVCF

The one I have is 405/625 I believe.
__________________
G8JET BVWS Member and V.M.A.R.S
HamishBoxer is offline   Reply With Quote
Old 16th May 2019, 12:42 pm   #4
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,511
Default Re: Sinclair Microvision from the NVCF

I very much doubt that. They made a 405 line prototype in the 60s but the ones you could actually buy were all 625 or 525 line. The earlier version had a UHF / VHF tuner but all the timebases were single standard.
Studio263 is offline   Reply With Quote
Old 16th May 2019, 12:44 pm   #5
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 5,106
Default Re: Sinclair Microvision from the NVCF

Well done for rescuing this! Thanks for the detailed write-up.

It is an amazing achievement for Sinclair. I seem to remember this was followed a few years later by a flat-screen version where the CRT gun was at the side of the screen, and the electrons were deflected through 90 degrees to hit the screen.
kalee20 is offline   Reply With Quote
Old 16th May 2019, 1:29 pm   #6
Argus25
Nonode
 
Argus25's Avatar
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,360
Default Re: Sinclair Microvision from the NVCF

That CRT is certainly unique. It would probably be the only CRT of that era, for television use, that was electrostatically deflected. I guess Sinclair would have had to have made that themselves, I cannot think of any other commercial small screen sets of this vintage that were not electromagnetic deflection. Electrostatic deflection is quite good and energy efficient for small sized screens, only a problem for screens a lot larger than 5". All the small 1" sized viewfinder CRT's that turned up in video cameras in the 80's, were mag deflected.
Argus25 is offline   Reply With Quote
Old 16th May 2019, 1:41 pm   #7
Richard_FM
Heptode
 
Richard_FM's Avatar
 
Join Date: Sep 2017
Location: Stockport, Cheshire, UK.
Posts: 866
Default Re: Sinclair Microvision from the NVCF

I've wanted one of these as the seem to be the best of the Sinclair TVs, but the ones I've seen on sale have always been more than I was willing to pay.

It's good that you managed to get it into working order from an oddly modified state.
__________________
Beware of the trickster on the roof
Richard_FM is offline   Reply With Quote
Old 16th May 2019, 2:17 pm   #8
McMurdo
Dekatron
 
McMurdo's Avatar
 
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 3,597
Default Re: Sinclair Microvision from the NVCF

Interesting, a cute little set, I'd have loved one as a child. Can we see a pic of it working?

The later ones with side-firing gun and angled phosphor were used in those wall-mounted video entry phones.
__________________
Kevin
McMurdo is offline   Reply With Quote
Old 16th May 2019, 4:30 pm   #9
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,511
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by Argus25 View Post
I guess Sinclair would have had to have made that themselves, I cannot think of any other commercial small screen sets of this vintage that were not electromagnetic deflection.
They were made by AEG / Telefunken, but to a Sinclair specification. The same tube was used in the Thandar(?) portable oscilloscope that RS Components sold for years.
Studio263 is offline   Reply With Quote
Old 16th May 2019, 4:31 pm   #10
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,511
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by McMurdo View Post
The later ones with side-firing gun and angled phosphor were used in those wall-mounted video entry phones.
It was the magnetically deflected Sony tube from the Watchman that was used in those.
Studio263 is offline   Reply With Quote
Old 16th May 2019, 4:47 pm   #11
Restoration73
Octode
 
Restoration73's Avatar
 
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 1,689
Default Re: Sinclair Microvision from the NVCF

I've not had mine apart, but can confirm the aerial terminals are like solder tags bent at
right angles so only the circular part is visible, and this has the hole tapped M2.5 with a
M2.5 x 6 slot screw and washer fitted.
Restoration73 is offline   Reply With Quote
Old 16th May 2019, 6:00 pm   #12
Richard_FM
Heptode
 
Richard_FM's Avatar
 
Join Date: Sep 2017
Location: Stockport, Cheshire, UK.
Posts: 866
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by Studio263 View Post
I very much doubt that. They made a 405 line prototype in the 60s but the ones you could actually buy were all 625 or 525 line. The earlier version had a UHF / VHF tuner but all the timebases were single standard.
I heard Sinclair proposed a portable TV in the 1960s which never went into production, only getting as far as some print ads, which I presume was the 405 line prototype.
__________________
Beware of the trickster on the roof
Richard_FM is offline   Reply With Quote
Old 16th May 2019, 7:07 pm   #13
Jac
Hexode
 
Jac's Avatar
 
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 482
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by Argus25 View Post
That CRT is certainly unique. It would probably be the only CRT of that era, for television use, that was electrostatically deflected. I guess Sinclair would have had to have made that themselves, I cannot think of any other commercial small screen sets of this vintage that were not electromagnetic deflection. Electrostatic deflection is quite good and energy efficient for small sized screens, only a problem for screens a lot larger than 5". All the small 1" sized viewfinder CRT's that turned up in video cameras in the 80's, were mag deflected.
The CRT was made by Telefunken, the type is D5-100WB. It also existed in a green version: D5-100GH. The heater is 0.55V at c. 60 mA.
The MTV1 has the same CRT.

Jac
Attached Thumbnails
Click image for larger version

Name:	2011-11-07 MTV1B 07 uitgekast.jpg
Views:	176
Size:	29.0 KB
ID:	183237   Click image for larger version

Name:	2015-01-08 MTV1 36 51 BB zk.jpg
Views:	165
Size:	37.3 KB
ID:	183238  
Jac is offline   Reply With Quote
Old 16th May 2019, 8:39 pm   #14
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 6,898
Default Re: Sinclair Microvision from the NVCF

Sorry! mine has the VHF/UHF Tuner,slight difference!NOT 405/625.
__________________
G8JET BVWS Member and V.M.A.R.S
HamishBoxer is offline   Reply With Quote
Old 16th May 2019, 8:53 pm   #15
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,435
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by Richard_FM View Post
I heard Sinclair proposed a portable TV in the 1960s which never went into production, only getting as far as some print ads, which I presume was the 405 line prototype.
Fourth image down here:

http://www.guenthoer.de/e-history.htm
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 16th May 2019, 9:05 pm   #16
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,435
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by Richard_FM View Post
I've wanted one of these as the seem to be the best of the Sinclair TVs, but the ones I've seen on sale have always been more than I was willing to pay.

It's good that you managed to get it into working order from an oddly modified state.
In about 1966 I built a mock-up in a soap-box of what I thought a pocket TV should look like, and took it to school.

The History teacher was convinced it was real.
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 16th May 2019, 10:45 pm   #17
Richard_FM
Heptode
 
Richard_FM's Avatar
 
Join Date: Sep 2017
Location: Stockport, Cheshire, UK.
Posts: 866
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by rambo1152 View Post
Thanks for the link it looks like an interesting site.
__________________
Beware of the trickster on the roof
Richard_FM is offline   Reply With Quote
Old 17th May 2019, 8:21 am   #18
mustangjohn
Diode
 
Join Date: Apr 2019
Location: Benowa, Queensland, Australia
Posts: 3
Default Re: Sinclair Microvision from the NVCF

Hi Guys I'm down under in Australia, and have 2 of the MTV1's I have one working but has poor RF, from what I read it's caused by the vari-cap diodes in the tuners (s), I had to replace the vertical transistors (4 off) to get frame deflection, the other one has a few damaged edge connector pins, and I have no idea where to get them, it also has a faulty ST3-01-03 IC, incredibly my brother has located some in UK and 2 are on their way to me, it would be nice to get a good quality copy of the circuit, the one I have is quite poor, cheers John.
mustangjohn is offline   Reply With Quote
Old 17th May 2019, 8:47 am   #19
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 3,004
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by Studio263 View Post
The same tube was used in the Thandar(?) portable oscilloscope that RS Components sold for years.
They were originally a Sinclair branded product: Then they were sold under the 'Thandar' brand and also as RS-branded, as were other former Sinclair test equipment products. I have one of the Sinclair branded examples, owned by me from new. Still works, but I am going to have to replace the rotary range / timebase switches as they have gone very noisy / intermittent (they are 'sealed' so there's no way to introduce switch cleaner).

There was some speculation that they were at least partly devised as a way of using up the unused Microvision tubes: The 'blue' appearance of the trace was achieved by putting a blue tinted graticule /filter in front of the plain white screen.
SiriusHardware is offline   Reply With Quote
Old 17th May 2019, 1:26 pm   #20
Richard_FM
Heptode
 
Richard_FM's Avatar
 
Join Date: Sep 2017
Location: Stockport, Cheshire, UK.
Posts: 866
Default Re: Sinclair Microvision from the NVCF

Quote:
Originally Posted by SiriusHardware View Post
There was some speculation that they were at least partly devised as a way of using up the unused Microvision tubes: The 'blue' appearance of the trace was achieved by putting a blue tinted graticule /filter in front of the plain white screen.
I know Sinclair made some other test equipment, particularly a digital multimeter which used a case from one of their calculators.

IIRC Sir Clive eventually sold off Sinclair Radionics to Binatone, who rebadged some of the unsold Microvision sets with their own name.
__________________
Beware of the trickster on the roof
Richard_FM is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 4:47 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.