EEVblog #554 - Sinclair FTV1 TV80 Flat Screen Pocket TV Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: December 03, 2013, 10:31:53 pm
content: 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.zipFlickr Photos:http://www.flickr.com/photos/eevblog/sets/72157638306245666/Info page:http://www.thevalvepage.com/tv/sinclair/ftv1/ftv1.htmGuy who worked on the CRT:

author: dr.diesel
author_rank: Super Contributor
timestamp: December 03, 2013, 11:12:40 pm
content: 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.

author: MartinX
author_rank: Regular Contributor
timestamp: December 03, 2013, 11:26:08 pm
content: 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.

author: jancumps
author_rank: Unknown
timestamp: December 03, 2013, 11:26:39 pm
content: magic

author: dexters_lab
author_rank: Unknown
timestamp: December 03, 2013, 11:27:47 pm
content: 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 waterThe 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

author: Zad
author_rank: Super Contributor
timestamp: December 03, 2013, 11:50:34 pm
content: 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.

author: free_electron
author_rank: Super Contributor
timestamp: December 04, 2013, 12:04:14 am
content: 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...

author: dentaku
author_rank: Frequent Contributor
timestamp: December 04, 2013, 12:15:43 am
content: 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?

author: TheEPROM9
author_rank: Frequent Contributor
timestamp: December 04, 2013, 12:28:14 am
content: 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.

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 04, 2013, 01:13:07 am
content: 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.

author: Scrambler
author_rank: Newbie
timestamp: December 04, 2013, 01:19:26 am
content: 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?

author: jolshefsky
author_rank: Regular Contributor
timestamp: December 04, 2013, 01:57:11 am
content: Just in time for Christmas ...... 1984, on.

author: sivalley
author_rank: Newbie
timestamp: December 04, 2013, 02:36:10 am
content: 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!

author: Chartreuse
author_rank: Newbie
timestamp: December 04, 2013, 02:37:02 am
content: Quote from: Zad on December 03, 2013, 11:50:34 pmRealistic (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.

author: ^Gecko^
author_rank: Newbie
timestamp: December 04, 2013, 03:00:54 am
content: 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

author: LoyalServant
author_rank: Regular Contributor
timestamp: December 04, 2013, 03:09:37 am
content: 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.

author: Zad
author_rank: Super Contributor
timestamp: December 04, 2013, 03:45:49 am
content: 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/LenslokWhen 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.

author: 84GKSIG
author_rank: Regular Contributor
timestamp: December 04, 2013, 04:00:44 am
content: 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 unitIts 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 qualityas always, I enjoy these tare down videos sinclair hey, have to see what I can dig up

author: Lightages
author_rank: Unknown
timestamp: December 04, 2013, 05:13:56 am
content: Some more Sinclair FTV1 porn:and one with some working video:

author: Sionyn
author_rank: Frequent Contributor
timestamp: December 04, 2013, 10:49:11 am
content: Clive got a phone call about dave's eevblog teardownOne 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.

author: Neilm
author_rank: Super Contributor
timestamp: December 04, 2013, 06:57:07 pm
content: 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.

author: Macbeth
author_rank: Super Contributor
timestamp: December 04, 2013, 08:05:27 pm
content: Quote from: MartinX on December 03, 2013, 11:26:08 pmIndeed. 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.

author: CJWarlock
author_rank: Contributor
timestamp: December 04, 2013, 08:06:22 pm
content: Very interesting teardown, I like 80's electronics too - thanx, Dave. I wonder if you'd like to do a Commodore C64 teardown somewhen.

author: Macbeth
author_rank: Super Contributor
timestamp: December 04, 2013, 08:12:32 pm
content: Quote from: sivalley on December 04, 2013, 02:36:10 amI 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.

author: c4757p
author_rank: Super Contributor
timestamp: December 04, 2013, 08:16:54 pm
content: Quote from: Macbeth on December 04, 2013, 08:12:32 pmThe schematic shows it directly tied to 1440V DC.

author: Macbeth
author_rank: Super Contributor
timestamp: December 04, 2013, 09:19:25 pm
content: Quote from: c4757p on December 04, 2013, 08:16:54 pmDidn't have a chance to check the schema, just me musing on how on earth it was done? The charge on those plates couldn't be changed so quickly (think big capacitor), so I guess the clever stuff was all done in the Ferranti and hand tuned using all those trimmer pots. It certainly was not as simple as an X/Y CRT like used in an oscilloscope, though not as complex as the driver circuitry, magnets, inductors, and shuffle rings used on a colour CRT.Thinking of oscilloscopes with vector rather than raster scan, I always wondered how the old Vectrex portable arcade game managed it in such a small form factor. I was amazed to see vector graphics back in the 1980's on such a machine - but it was way too expensive for my family, never mind the cost of the game carts. I loved the old Atari vector graphic arcade machines like Battlezone, Asteroids, etc. I notice Vectrex are still pretty darn expensive as '80s nostalgia on ebay.Aww, heck, even in the early 1990's I was amazed when I saw Hameg CRT storage scopes with proper vector drawn readouts for timebase and volts. I had only learned on very badly calibrated Telequipment D61's at college back then.

author: Terabyte2007
author_rank: Frequent Contributor
timestamp: December 04, 2013, 09:31:23 pm
content: Awesome! Gotta love the 80's.

author: tecman
author_rank: Frequent Contributor
timestamp: December 05, 2013, 02:11:54 am
content: Quote from: N2IXK on December 04, 2013, 01:13:07 amActually the Sony series used magnetic deflection for both axes. The other interesting feature of the Sony and I assume on the sinclair as well is a trapezoid signal applied to the horizontal deflection, based on the vertical scan. In operation the bottom of the screen, closest to the gun, required more deflection than the top, since it is a shorter distance. They modulated the sweep to apply this compensation.paul

author: EEVblog
author_rank: Unknown
timestamp: December 05, 2013, 02:22:58 am
content: Quote from: Macbeth on December 04, 2013, 08:05:27 pmWhy would I?I have almost zero experience with TV's, monitors, or CRT's in general.I don't come from the consumer repair or monitor design industry.Never had to design one, never had to repair one.

author: EEVblog
author_rank: Unknown
timestamp: December 05, 2013, 02:30:17 am
content: Quote from: Macbeth on December 04, 2013, 08:12:32 pmNo, it's a fixed voltage field.

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 05, 2013, 02:40:01 am
content: Quote from: tecman on December 05, 2013, 02:11:54 amThe tube I was referring to was the original design, Sony designation ED15. Electrostatic in vertical, electromagnetic in horizontal. The internal ferrite bars were used as both the horizontal magnetic pole pieces, but also as the vertical electrostatic plates. Covered in Pete Keller's CRT book, along with the Sinclair tube, and dozens of other obscure and downright bizarre CRT types developed over the decades.http://www.amazon.com/The-Cathode-Ray-Tube-Technology-Applications/dp/0963155903

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 05, 2013, 03:04:40 am
content: Quote from: EEVblog on December 05, 2013, 02:22:58 amThis is the whole reason that the horizontal output transformer (Line Output or LOPT) in a CRT set is commonly referred to as the "flyback" transformer.The horizontal sweep waveform is a sawtooth. At the end of each scan line, the horizontal output transistor/tube gets suddenly cut off, and the collapsing magnetic field in the yoke winding and transformer core creates a high voltage pulse when the beam "flies back" to the left side of the screen. This pulse is then rectified (originally with a simple diode tube like a 1B3 or 3A3, later with a Cockroft-Walton multiplier housed in a potted "tripler" module, and eventually a diode string integrated into the transformer itself)), and used to provide the second anode or "ultor" voltage for the CRT.My first real job in electronics (during high school) was part-time bench tech at a local TV shop. Learned how to fix the things as a source of extra income as a kid. I was always scrounging dead sets from the curb to strip for parts for building stuff, and eventually read enough and played around with enough different sets that I could fix quite a few of them for little to no cost, and sell them at garage sales/flea markets. Of course, this was in the days that there was actually a market for used TV sets.Got out of consumer electronics just as the first wave of "disposable sets" (single PC board and all plastic cabinet) started to hit from Japan and Taiwan. The writing was on the wall back in the mid-late 1980s, and the consumer electronics repair industry is pretty much dead today. Glad I headed for greener pastures (broadcast/industrial video, then scientific instrumentation) when I did, that's for sure.Still like to play around with vintage video as a hobby, though. Am currently restoring a 1948 RCA Victor 10" TV....

author: EEVblog
author_rank: Unknown
timestamp: December 05, 2013, 03:36:22 am
content: Quote from: N2IXK on December 05, 2013, 03:04:40 amMy first full time job at 17 was as a repair and testing tech on security gear, so mostly digital and processor stuff, but that included video, and slow scan video too. So I knew all about video signals, but I've never touched a TV CRT, and never had any real interest in them personally.

author: RupertGo
author_rank: Regular Contributor
timestamp: December 05, 2013, 06:15:29 am
content: The correction waveform needed to create a linear picture on the Sinclair flat tube phosphor was extremely complex. Company legend had it that the the engineers responsible modelled it by ray-tracing the electron beam in software running on one of the company's ZX80 3.5 MHz Z80 computers, but the process was unsurprisingly quite slow. A quick calculation showed that it would take longer to complete the task than was available in the lifetime of the project (in fact, had they known it, the lifetime of the company)... so they ported the code onto a Cray supercomputer they rented time on. Thought to be the most dramatic hardware-based speed-up on record.Sinclair really wanted to use that flat-screen technology in everything, but he could never make it work in colour (the closest he got was a rather odd red/green device that showed everything in a kind of sepia) or any bigger than the size in the TV. There were experimental 4" tubes, but the trouble there was the very large expanse of flat glass with vacuum on one side and 1 atm pressure on the other. You were advised to wear safety glasses if you came anywhere near them...

author: Frantone
author_rank: Regular Contributor
timestamp: December 05, 2013, 05:32:53 pm
content: Hey Dave - good for you moving comments here!I noticed something familiar in your EEVblog #554 about the Sinclair flat screen - the CRT tube looks as though it uses the same kind of C-clamp type spring clip lead for routing the power to the inside of the tube as that which the LVDC surface mount devices used.It was in my part two LVDC teardown that I accidentally discovered that those logic device leads were held by spring tension to deposited metallic contacts on the top and bottom edges of each ceramic wafer rather than soldered there. I found that the packages could be slid out of the leads. Who knew?! The Sinclair tube appears in the video to be using this same kind of thing, it appears that way anyway. First used for the Saturn V!http://www.frantone.com/designwritings/design_writings7.html#LVDC2

author: silicon junkie
author_rank: Newbie
timestamp: December 05, 2013, 08:09:42 pm
content: Just looked at the vertical and horizontal drive signals on a scope, they are stepped as if they are coming from a D-A.Perhaps this is how they got the scan correction sorted, they use a look-up table to adjust the waveform shape.The repeller voltage is a fixed DC voltage with a little bit of line scan ripple.

author: EEVblog
author_rank: Unknown
timestamp: December 05, 2013, 09:12:10 pm
content: Quote from: Frantone on December 05, 2013, 05:32:53 pmPresumably the reason is an anti-vibration type mechanism so as not to crack the joints?

author: RupertGo
author_rank: Regular Contributor
timestamp: December 05, 2013, 09:22:14 pm
content: Yes, I'm (almost - been years) sure that the scan waveforms come from a precomputed LUT in the IC driving DACs. I don't know how big that table is - be really interesting to find out the details.Frantone, I had no idea those clips (which pop up all over the place once you look for them) were a Saturn V design! I know that a lot of packaging and basic logic ideas came from the Apollo project but I've never seen a comprehensive list.As for the LOPT transformer also producing the EHT for TV CRTs - I always thought of those as the precursor to SMPSUs, but then as one of those kids who fixed TVs as a summer job during their school days, TV circuits were the first seriously complex electronics I came into any sort of contact with.When the idea was introduced (I think in the 50s), it was certainly a big step-up (sorry) from the mains transformer + massive overwind that did the job beforehand. As was the adoption of the voltage multiplier, which meant you weren't directly rectifying 25KV (in the case of early colour) and thus not producing unearthly amounts of X-rays. Those early sets were a lot more like particle colliders (with the gun facing your living room!) than is comfortable to think...

author: Frantone
author_rank: Regular Contributor
timestamp: December 05, 2013, 10:04:29 pm
content: Quote from: EEVblog on December 05, 2013, 09:12:10 pmThat's an interesting observation and perhaps true - I really don't know honestly. I was very surprised when I found this out. There were hundreds of pages in the system and thousands of logic devices - and tens of thousands of pins. I would imagine the only reason would be stability - though I would think that some kind of through hole soldered pins in the ceramic base would be preferred, as they did use through hole pins for the IBM system 360 SLT device packages. But these clip leads obviously do work and were used for some good reason - the Saturn was designed by very very smart people - and they obviously were the choice for that glass tube!

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 05, 2013, 11:52:23 pm
content: Pretty sure that that basic contact design predates the Saturn V by a decade or so.Have seen those type contacts used on early thick film RC networks called "Couplates" or "PECs" (Packaged Electronic Circuits), which were ceramic wafers with several resistors and caps integrated into a single module, used in a lot of 1950s era tube gear for coupling networks, filters, integrators, etc. Nowadays, you still see them on thin film resistors/dividers, such as the rectangular ceramic ones used in DMM input stages.I think it is a fairly standard way of attaching metal leads to a glass or ceramic substrate. The spring action is likely to compensate for the differences in thermal expansion rate between the metal and the substrate.

author: JackOfVA
author_rank: Unknown
timestamp: December 08, 2013, 09:04:23 pm
content: I assume the mention of "D. Gabor" a university professor, was an inside joke.That would be Dennis Gabor, Nobel Prize in Physics for holograms. He also worked with CBS Laboratories (the US broadcast network) and I believe that relationship is the genesis of the flat display screen technology used in the Sinclair TV.

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 08, 2013, 09:44:46 pm
content: The Sinclair tube seems closer to the Aiken design, with the electron gun to the side of the phosphor screen, rather than below it, as in Gabor's design.http://en.wikipedia.org/wiki/Aiken_tubeBoth the Aiken and the Gabor designs are also covered in the Keller book.

author: PChi
author_rank: Frequent Contributor
timestamp: December 09, 2013, 08:51:05 pm
content: Before anyone gets too nostalgic about Clive don't forget that the general public forked out cash for developing Sinclair products. The paperback 'Sinclair and the 'Sunrise' Technology' by Ian Adamson and Richard Kennedy is a good read.