Hi all.
Í am trying to bring back to life, this ancient tv.
After fix several classics problems (dirty contacs, broken cords...) now the tv lights up and I see snow in the screen. We have a bright raster.
Please, What is the function of the two rotating metal pieces, in the neck of the CRT?
Best from Spain.
Albert
@alcruma
Those flat metal plates are“Picture shift “ controls, they move the raster up/down, side to side to put the picture in the correct place on the screen.
Leave those controls alone until you have a locked picture on the screen, you can then adjust them if required.
The one the neck of the CRT one near the base is an ION Trap magnet, it’s adjustment is critical and can damage the CRT if incorrectly adjusted, if it appears not to have been moved leave it alone.
Frank
Hi Frank. Thank you so much for your help.
I ve not touch the ion tras magnet..
When I began to repair the tv, there was an open circuit in the mains pluging. I found the power on/off switch damaged, (that, was easy). Then, with that fixed, valves began to lit, but no raster in screen. Just a nasty hum in the speaker.
I look for the EHT, but no sparks from the horizontal valves. I found and open resistor in the screen grid of the PL81. With a new resistor, bingo, I get little sparks from the PL81 and PL81 anode, but NO raster.
I test the Horizontal transformer, and seems to be ok.
Only, when i switch power off, I could see a bright central point in the screen.
Time to change ALL the old wax paper capacitors. After 70 years, all were leaky.
This was deffinitive. With new ones, EHT looks good, the oscilloscope signals in the horizontal and vertical circuits, looks great...BUT I only could see a raster very small. Only 3 inches height.
Here, I was lost. Just for Luck, I move the flat metal plates and...OOHHHH. i get a nice, perfect and bright raster.
After 70 years, CRT seems to be in almost new condition. Bright is VERY hight.
Next step, get a RF video source, and test the video stage.
This tv is Hot chassis, so I need and isolated video font, or, a RF one.
Any advice welcome.
All the Best. Albert.
@alcruma
You are doing a really good job, probably can’t get much further without an RF video source.
Frank
Hi Frank. You are very kind.
Im thinking to use a old pong tv play, witch have a rf output, ready to use in the old analogic tv sets.
This tv set, only can receive vhf.
Also, i,ve build with a IC, a simple pattern generator with several square waves and works very well. It generates eight vertical bars BUT I,m having trouble doing the RF part.
Ok. Thanks for your help and forgive me for destroy your English languaje. 😀
Albert
Similar picture shift plates and no doubt scanning coils were used in 1957/8 UK made Philips and Stella TV sets. Sets that employed the AW43-80 and AW53-80 90 degree CRTs.
UK models Philips 1768U, 2168U and Stella ST8617U.
Till Eulenspiegel.
