Progress ...
I'm pleased to say I now have a picture of sorts on the Sobell. Working my way through and replacing the worst of the leaky capacitors.
The picture signal is being fed into the video amplifier grid circuit.
One of the small brown stupid hunts in the RF section popped when I applied power, I guess it is o/c now and I'm not sure which one it was. I imagine i'll be changing quite a few before I'm finished.
The set perhaps uses an ECL80 for mixer oscillator, I cant be sure just yet not hiving the schematic.
Most of the RF/IF coils are in compartments under the chassis with the cores accesible from the top.
The EHT regulation is very poor when the brightness is up hight the pictue baloons quite badly.
Main HT is around 200V, Boost voltage is now 430v, there was nothing until I changed the boost capacitor.
there is at least 10kV EHT according to my uncalibrated home made EHT probe.
There was no brightness until I changed the brightness decoupling capacitor.
There is no flyback suppression, and the vertical height and linearity are still quite wrong.
My photo record is here: Sobell T143 photos
The case is still polished in places, a couple of small scratches to hide.
One thing completeley missing is the bottom cover, is this wood, tv fiberboard like the back or something else?
The bulge on the back protecting the tube base is also missing.
I'll see if I can get sound on it now. There is a sticker on the cahssis saying it is tuned for WENVOE, which is channel 5, so should be 63.25 MHz sound, 66.75 MHz vision.
Kind regards, David.
I'm pleased to say I now have a picture of sorts on the Sobell. Working my way through and replacing the worst of the leaky capacitors.
The picture signal is being fed into the video amplifier grid circuit.
One of the small brown stupid hunts in the RF section popped when I applied power, I guess it is o/c now and I'm not sure which one it was. I imagine i'll be changing quite a few before I'm finished.
The set perhaps uses an ECL80 for mixer oscillator, I cant be sure just yet not hiving the schematic.
Most of the RF/IF coils are in compartments under the chassis with the cores accesible from the top.
The EHT regulation is very poor when the brightness is up hight the pictue baloons quite badly.
Main HT is around 200V, Boost voltage is now 430v, there was nothing until I changed the boost capacitor.
there is at least 10kV EHT according to my uncalibrated home made EHT probe.
There was no brightness until I changed the brightness decoupling capacitor.
There is no flyback suppression, and the vertical height and linearity are still quite wrong.
My photo record is here: Sobell T143 photos
The case is still polished in places, a couple of small scratches to hide.
One thing completeley missing is the bottom cover, is this wood, tv fiberboard like the back or something else?
The bulge on the back protecting the tube base is also missing.
I'll see if I can get sound on it now. There is a sticker on the cahssis saying it is tuned for WENVOE, which is channel 5, so should be 63.25 MHz sound, 66.75 MHz vision.
Kind regards, David.
