Well I have finally wrangled the chassis to the point of showing a cute little picture on the CRT.
I knew nothing about how a PAL system TV worked (despite having built the 5 inch set!) but this time had to go into the specifics a bit deeper to get a stable picture. I know this set is really just a monitor for a set top box but building it has opened my eyes as to how important the various parts of the transmitted signal are.
I realise this is an obsolete system, even back in the 1980's we were memory mapping pictures on our computers not running from signal streams and I guess that's what modern Television is where we are today. With a working chassis its time to stop and sign it off and wrap a cabinet around it and call it a finished project. I suppose the ultimate would be to work out a valve front end to take the signal from the antenna as the set top box does. I'm not sure if anybody has ever done that. Even the original 5 inch set used a store bought tuner box and the IF strip from a commercial 17 inch wreck, I may have rolled my own then but that was just beyond my abilities and resources. I'll do a bit of study to try and understand what sort of signals come out of an antenna now but that is not my top priority, probably just some theoretical thinking.
I'll finish off a PDF of part 4 and send that to Brad and you can see how I make basic goofs in electronic design and then work my way out of them again.
Cheers, Fred.

3 inch TV - The Build

Hello Fred,
You've been busy.
I always thought you must of been a TV technician, because you seem to know a lot about TVs.
What was your profession???
Electrical Engineering? ???

Pete

Hi Pete you will laugh at this but no, i'm a jack of all trades and master of none!
I did start an electrical apprenticeship as I had to work to survive as a 15 year old and an old friend of my family took me stupid Freddo on.
That may sound a bit strange but we had no money, nothing, and a government aptitude test when I walked out of school, and never went back, found I was suited for nothing but to be a gardener or cleaner. That may sound strange but a 'different needs' person was simply not known back then, the 1950's, so you were just classified as stupid. I did find the papers from my aptitude and IQ test much later in life and found I was rated as 'superior 'in all but one field and an IQ of 145 despite not completing any of the mathematical section of the test since I did not understand numbers at all. (still don't , thank god for calculators). Thanks a lot fellers. I remember doing the test and finishing about 30 minutes before anybody else where most people were still struggling. Anyway, I sort of finished the apprenticeship but for health reasons missed the final exams and guess what, yes no second chance, no paper. Thanks fellers. But by that time the electronic revolution was starting so I booked into various tech college courses to do with that subjects ( bluffed the entrance exams) and worked for a power generation company, designed stuff, learnt to weld and machine, learnt CAD, made guitar amps and sold them and worked for a friend in a little electronics business that sold hobby parts. Try working those 3 jobs now!! By that time I simply was the design guy that told them all how to build stuff and what was wrong with stuff and had a large 'shed' in my back yard which you could probably have called a laboratory and made my own PC boards and just made stuff or made protoypes or fixed things that nobody else could fix.
Sorry guys I am boring you with a long story but the nuts of it is no, I don't have any papers, don't know nothing, but seem to wind up telling them all how do things! Management used to hide me when the auditors came around checking everybody's credentials . When they came looking for the designer, or the drawing office guru or the R&D man or the estimator he would always be out on site or on holidays!!
So from the official point of view i'm not capable or licensed to wire a s&*t house light up but I could design a rocket launcher or a power house (and make it) with no problem!
Cheers, Fred.

Fred I was much like you, never could get my head around mathematics until I discovered you could model a TV line deflection system with a 2nd order differential equation. Just plug the numbers in and predict what would happen.

The light went on big time! Finally, a use for all this stuff!

Now if you want a really BIG project, let's make a digital TV receiver using only valves. My guess is it would take a medium-sized room to hold it and consume 4 or 5 kW., while working at the most basic level without motion prediction. In other words a $20 box you could fit in your pocket would massively out-perform it.

Hi Fred,
No I dont find that strange or odd at all Fred, because I come from a similar type background and family I was very wild as a teen and a kid, my old man died at 45 and so I was a bit wild, my school days were spent at the beach .or on trail bikes
I also left school at 14, At 15 I got a job in a Engineering firm that built sports cars and racing cars.
They also did restoration work on vintage cars.
They took me on to be their mechanic, I also lived on the work premises as it was cheap board and I had no way to get to work otherwise. But , because it was a complete car fabrication workshop ,I was able expand my training also into ather areas, so I can spray , 2 pack ,Acrylic, build complete bodies, I was their Welder for chassis building ,mainly Mig work ..steel.
But I got out of all that years ago and I went into furniture and antiques and I did that for many years and still do on a small scale.
I had to be self employed because as time has gone by, jobs in the car industry or manufacturing industry became harder and harder to get!! All the people I use to know have closed up the workshops and now there was new kids on the block .
You know how it is !!
As for electronics I know nothing !
Only what I have learnt off Ian .
But I never regretted learning furniture restoration, because I enjoy it very much .
What I will do for an income in the future ? I have no idea !
The world has changed so much ive become obsolete knowledge.

Pete

Yes Ian I suspected as much! The Motorola 6800 series of chips and the Z80 were all a revelation when they first appeared and we made up computers like the "DREAM" with bit mapped arcade games. (I wound up repairing badly assembled customer kits for Bill Edge and JR John Reilly for $30 a go! whoohoo! so I guess I must have become a "computer expert"!!!!!) The power you had then from a microprocessor and the size compared to the previous generation of computing with valves like the room full of twin triodes at Sydney Uni in that Siliac thing, and that was flat out adding 2 and 2! A bit harsh saying that I guess, but seeing what would be required to process a digital TV signal you would need a room full of Twin Pentodes at least!
I did get as far as quadratics and saw the sense of 3 term equations but the mathematics of things like logarithms I just don't understand and pure maths was like an alien language. I had a Brother in law that was a maths and physics graduate and I could sit for hours listening to him talk and not learn a thing!
Back to the PAL TV sets, I guess we will just have to be content with building MONITORS and hiding the digital smarts where the twin valve tuner used to go. Just as a teaser I was looking at a 6" style long persistence CRT with thick green/yellow glow in the dark screen phosphor and thought that would make a cool rotating RADAR display unit!! Now that is a VALVE base technology I could handle.
Fred.

Document uploaded.

Fred I am MIGHTILY impressed!

Thanks Ian, I surprise myself sometimes!
Its only by doing and seeing that I can convince my self that a certain thing works the way the books say.
Lucky I have spent my whole life making prototypes from stuff whether it be a mechanical or electrical thing and have a shed where the bit I am looking for to make something is probably laying on the floor or on a shelf somewhere. In my area the council have just announced there will be no more kerb side clean ups where you can find that part you are looking for disguised as something else and that will be the death of us kerb side parts warriors!
I just realised that old microwave ovens are actually fitted with medium EHT filter capacitors for 1940's 2Kv CRTs, (1.0Uf with an inbuilt 10mohm bleed. )That made me crawl over the shed "now where did I stick those old pie cookers?" OH NO, gone in that last big clean up I had....! Must go for a drive to the next county and see what I can see.
Guys, I like writing about my exploits with valves and often wonder whether the style of writing makes sense to readers as in getting the technical point across? Just because something makes sense to me doesn't mean its clear to someone else!
AND if I don't make sense or have some detail wrong don't hesitate to point that out, its all a process of learning, I wont burst into tears, its the facts and the truth i'm after so my brain halves agree and don't bicker so much!
Fred.

Finally back in the workshop after a couple of weeks sick and put a microwave cap into the 3" TV.
Works fine and reduced the EHT ripple on the screen so that the tiny credit lines that come at the end of the show can be read.
The capacitor has an internal 10megohm bleed and is rated at .75μF and 2100V 50 cycle.
In this circuit the cap is the first filter and connected straight to the top cap of the 1S2 diode.
When switched off the EHT voltage discharges down to low volts after 5 seconds or so.
The cap ran at ambient temperature after an hour so there is no problem anywhere.
Much better than my dodgy 40 year old "Di-Pol" caps!
I'll send Brad a photo.
Fred.

Its one thing I find harder with valve gear it the wiring I get lost with out a schematic more so that circuit board builds .
Its but really nice to see a clean new valve project before the years dust gets to it .
i am looking if there is more to the build .
On 2 of my CRT projects I just used a chinese bug zapper and a 317 to control the EHT get about 6 or 7kV out them 3 volts in but it is more fun to make the unit from a fly back transformer.