EEVblog #554 - Sinclair FTV1 TV80 Flat Screen Pocket TV Teardown

[EEVblog]

Dave tears down a vintage 1984 Sinclair FTV1 / TV80 pocket TV and explains how the innovative 3 deflection system flat screen CRT works.
Service Manual with schematics and theory of operation:
http://eevblog.com/files/Sinclair_FTV1.zip
Flickr Photos: http://www.flickr.com/photos/eevblog/sets/72157638306245666/
Info page: http://www.thevalvepage.com/tv/sinclair/ftv1/ftv1.htm
Guy who worked on the CRT:

[dr.diesel]

From mailbag Monday to teardown Tuesday, back to back, this one holds the record!

FYI, Clive Marles Sinclair, born 30 July 1940 (age 73), still among the living.

[MartinX]

I did not know this thing ever existed, amazing! And yes using the horizontal output stage as a power supply is very common in CRT screens.

[jancumps]

magic

[dexters_lab]

Nice!

I bought one of those new in the 80s, i think i bought it in Boots. Sadly mine was stolen in a house break-in during the late 1980s or i would still have it.

The lithium packs were made by polaroid, came in a pack of three for i think £9. They had a very distinctive smell and did not like being punctured and then dropped in water 

The power jack was useful in combination  with a 12v car adaptor. Meant you could watch tv while in the car without draining the battery.


The picture quality was good, better than the lcds of the time, but lacked contrast

[Zad]

Can you believe that Sinclair was actually developing this concept to use in portable computers? Amazing! The Sinclair Pandora was under development for several years, but as you might expect LCD panels got to be cheap and effective quite quickly. The result was the Z88 (see previous teardowns). I think Sony used a very similar flat CRT in their security entryphones, but the screen on those was actually curved rather than bending the beam inwards. I wonder if they did that to avoid paying royalties on the patent.

Here we are:



Note the magnetic coil deflection system. Power consumption wouldn't be an issue on fixed units like these.

[free_electron]

Too bad analog transmission was turned off yesterday , before the teardown.
ah well. relics of a bygone era.. analog tv , glass tubes , pulled vacuum with bits of scrap metal in em...

[dentaku]

I see that many of the resistor leads were coated different colours.
Is that just to make sure the don't touch anything accidentally because they're mounted vertically or is it some kind of shielding?

[TheEPROM9]

That CRT is a thing of beauty, I did wonder what they looked like inside as from the outside it is clearly visible that a non standard package is used. The design reminds me of a VFD internal structure which is fitting as VFD's used similar principles of operation to VFD's. Sony's flat CRT is of a completely different design because the screen is bent so the beam will hit without any third state of deflection. That has to be the coolest CRT I have ever seen, I would love a collection of those CRT's.

[N2IXK]

Sony's flat CRT for the "Watchman" TV sets was very unusual, in that it used electrostatic deflection for one axis, and electromagnetic for the other. The pole pieces for the magnetic axis were ferrite bars enclosed inside the envelope, with only the coils external.

[Scrambler]

Hey Dave, since there's just a main IC taken out, but everything else is still here, maybe you can build an oscilloscope out of it?      What would it be? Transformation Thursday?   

[jolshefsky]

Just in time for Christmas ...... 1984, on .

[sivalley]

As someone else beat me to saying scan signals are commonly driven by the same signal as the HT drive circuit, I'll add it's only used in the horizontal (or in this case line) drive since they have to operate in the 15+ kHz range.  Anyone else ever get driven, no pun intended, nuts by the the ringing noise given off by the flybacks in old CRT TVs?

I have to wonder about the repeler system though.  I wonder if it used a static voltage or if it swept as well.  Since it's safe to assume the electrons are all travelling at the same speed regardless of deflection angle (but not vleocity ;-) ), you wouldn't need as strong a repulsion voltage at the far end as you would the near end (referenced from the line deflection plates).  Of course it's easy enough to use the line signal to synchronize this but it would be in reverse magnitude in relation to the line sweep.  My brain SPICE isn't able to make it out looking at the schematic, but it would surely be something that would affect the astigmatism of the image.

Too much loon? Cheers! 

[Chartreuse]

Can you believe that Sinclair was actually developing this concept to use in portable computers? Amazing! The Sinclair Pandora was under development for several years, but as you might expect LCD panels got to be cheap and effective quite quickly. The result was the Z88 (see previous teardowns). I think Sony used a very similar flat CRT in their security entryphones, but the screen on those was actually curved rather than bending the beam inwards. I wonder if they did that to avoid paying royalties on the patent.

Note the magnetic coil deflection system. Power consumption wouldn't be an issue on fixed units like these.

Realistic (Radio Shack) also used that same curved CRT with magnetic deflection in their Portavision Portable TV (#16-116) which ran off of 4 C cell's. Give me a few seconds to find where I placed it and I'll grab some pictures. Was the TV I watched Canada's Analog shut-off on. I did watch the local stations quite a bit in the year after I bought it until the signals went dead. You don't really notice the curve while watching it and surprisingly the "pixels" don't stretch near the top. It's not as fancy as Sinclair's but it gets the job done in roughly the same space.

[^Gecko^]

It's not actually a fresnel lens, it's an anamorphic lens (think "Cinemascope".)  Fresnel lenses are flat and have steps, to simulate a much thicker spherical lens (invented by the french guy for lighthouse lens systems.)

Torrance

[LoyalServant]

The coating is probably done this way as demonstrated by Ben Krasnow:


He is using this to make his own custom LCD displays as well.
Good stuff.

[Zad]

Having Googled for photos of the lens, it does indeed look like a smooth anamorphic lens. You know, I could have sworn it was a fresnel! Just goes to show how your memory can play tricks on you. My brain is probably confusing it with the Lenslok protection system. http://en.wikipedia.org/wiki/Lenslok

When I was a teenager repairing televisions for a year before uni, I could diagnose some PSU faults from the noise it made. The 15,625Hz whistle could be really annoying from some models, but you could tell if they weren't synching or were cutting out or overloaded. If you are over 30 though, the high frequency hearing response really tails off, even for those of us not really exposed to much loud noise.

[84GKSIG]

loved that video. reminded me of a little CRT I pulled from an old video intercom system, still have it too, hours of good fun. i always looked at it as a mini electron beam projector and screen in one unit 
Its very similar to the one posted on the first page with the magnetic deflection coil.
some pics and a video from a while back in terrible quality 







as always, I enjoy these tare down videos sinclair hey, have to see what I can dig up 

[Lightages]

Some more Sinclair FTV1 porn:

and one with some working video:

[Sionyn]

Clive got a phone call about dave's eevblog teardown



One off-drama which looks at how Sir Clive Sinclair took the world by storm in introducing affordable home computers, and the ups and downs of competing in an ever evolving market.

[Neilm]

I've actually still got one of those. I powered it up just before they turned off the analogue signal here in Blighty - it still works.

[Macbeth]

I did not know this thing ever existed, amazing! And yes using the horizontal output stage as a power supply is very common in CRT screens.

Indeed. I am quite surprised Dave didn't quite know this. The Line Output Transformer would generate all the required LV, HV, and EHT required in a CRT TV/Monitor, including a tap regulated by a 33V Zener for the "tuning voltage" going into the tuner can. Of course back in the earlier days (1970's) these voltages would be generated by a furnace of a wirewound high current low ohm dropper resistor that consumed as nearly much electricity as a bar fire!. Live mains chassis too. ahhh... the good old days.

In the trade (I was a bench service engineer in the early 1990's) the flyback transformer was known as "The Lopty". Invariably most faults with dead sets were down to the MOSFET chopper transistor that powered the darn thing. Also, LOPTY had the A1 and FOCUS pots embedded within it for the CRT.

[CJWarlock]

Very interesting teardown, I like 80's electronics too - thanx, Dave. I wonder if you'd like to do a Commodore C64 teardown somewhen.

[Macbeth]

As someone else beat me to saying scan signals are commonly driven by the same signal as the HT drive circuit, I'll add it's only used in the horizontal (or in this case line) drive since they have to operate in the 15+ kHz range.  Anyone else ever get driven, no pun intended, nuts by the the ringing noise given off by the flybacks in old CRT TVs?

I have to wonder about the repeler system though.  I wonder if it used a static voltage or if it swept as well.  Since it's safe to assume the electrons are all travelling at the same speed regardless of deflection angle (but not vleocity ;-) ), you wouldn't need as strong a repulsion voltage at the far end as you would the near end (referenced from the line deflection plates).  Of course it's easy enough to use the line signal to synchronize this but it would be in reverse magnitude in relation to the line sweep.  My brain SPICE isn't able to make it out looking at the schematic, but it would surely be something that would affect the astigmatism of the image.

Too much loon? Cheers!

I agree. I was thinking of the exact same thing all along. Surely the repeller had to have a swept EHT charge linked to the flyback? The alternative is some clever timing in the Ferranti IC to deal with distortion.

[c4757p]

I agree. I was thinking of the exact same thing all along. Surely the repeller had to have a swept EHT charge linked to the flyback? The alternative is some clever timing in the Ferranti IC to deal with distortion.

The schematic shows it directly tied to 1440V DC.