As my first post, I should introduce myself as a vintage technology enthusiast (particularly TV) from way back. Being in Australia, the oldest commercially made sets date from 1956, though I have imported a couple of earlier sets from the U.S.; a mirror in the lid 10" set and a 7" cheapie, which can be seen on my website
https://www.cool386.comIt's been a long time in the making, but I've finally finished my 'sort of a clone' of a Baird Televisor. I've had a fascination with mechanical TV since my school days, but it's only as time went on and I had access to a well equipped workshop, that I could make a proper go of it. I've been through the cardboard/plywood/gramophone record scanning disc experiments, but not with any success in my younger years. To cut a long story short, I later built up a Televisor for the Baird format, using the measurements from "Television for the amateur constructor". I believe the baseboard and disc dimensions are identical to the Plessey Televisor marketed by Baird. I took pics of my creation, as it was a few years back, which can be seen here
https://www.flickr.com/photos/13469158@ ... 8070450870
- televisor
I've got a proper sync circuit using the 375Hz line pulses. Although my transmitter (yet to be completed) will provide blacker than black sync pulses, my receiver would no doubt work on Baird's black level 'sync' pulses. The design is loosely based on that used for the CBS colour wheel receivers, using a 12AU7 phase detector to compare the sync pulses with pulses coming from a separate set of holes in the disc.
- sync lamp
The error voltage controls the motor using a 6J6 cathode follower to drive a 2N3055 in series with the motor. Light source was originally a 4W fluorescent tube which gave the right colour and had good brightness, but at the time I didn't take into account the phosphor persistance. Having now switched a 44 LED array, the difference is like between night and day. And the LED's are easy to modulate with the existing 6EM5 output stage.
Circuit of the whole thing uses 6 valves and 4 transistors. I'm more than happy to go into further detail about the design if there's any interest.
Anyway, since I've not completed the transmitter, the question arises of what video signal to feed it. All I have are 375Hz sync pulses, which of course just gives a black bar and blank raster, and some old 32 line files I downloaded from somewhere (possibly even here?). Problem is they only run for 5 seconds, and the 32 line signal is of course not properly compatible (the sync works great though!). To view the 32 line video on a 30 line disc requires the disc to be run at 13.33fps instead of 12.5fps in order to get the correct line rate 400Hz, but of course the result is a slowly rolling picture from right to left, since the frame rate is now too fast.
As you can see, my hole marking out wasn't as accurate as I'd like - such is the use of hand tools - but as I bolted both transmitter and receiver discs together when I drilled them, I'm hoping the errors will cancel out once I have my own signal.
- nbtv
- pic1.jpg (192.27 KiB) Viewed 7464 times
https://youtu.be/TL5le6Sujkg
- girl
- pic2.jpg (192.64 KiB) Viewed 7464 times
https://youtu.be/IhmrreLmxlYSo, my question is - where can I get a 30 line signal? I might come across as an eccentric nutcase, but I genuinely want to watch real TV on this set - sit down for a 2hr James Bond movie, etc. (All of my TV viewing is actually on vintage sets, though of the electronic kind). Some years ago there was a standards converter that would produce every kind of vintage video format - including Baird's. Is this still available or has something taken its place? While vintage TV and electronics is second nature to me, anything microprocessor is not - and because of the vastly different formats I can't see any other practical way to do the conversion. I presume one would have to store the horizontal scanned 625 line pic (or ignore interlace and treat it as 312.5 lines) and then read it out as a 30 line vertical scanned signal with the edges cut off.