21 inch Austrian TV (Hornyphon) working agian
 

I reported in my introductory message as a new member that I had high voltage problems with my 21 inch, 1957 Austrian Hornyphon (a Philips subsidiary) set. I was finally able to trace the problem and get the set working again. This may very well be the only working set of this kind in the US. It's a 220V, CCIR 625 lines / 50 fields TV.
The fault was in the filament circuit for the high voltage rectifier tube (DY87 = 1S2A). The filament voltage is generated by a single winding of high voltage cable around the core of the flyback transformer, quite a common way to generate the heater voltage superimposed on a 17KV high voltage potential. The circuit diagram showed a 1.4 Ohm resistor in series with this winding. I disassembled the high voltage rectifier tube holder with socket and found the resistor glued into the center hole of the tube socket, and the tube socket pressed into the plastic insulator tube. It was a wire wound resistor, the wire being thinner than hair. The resistor had become open, unfortunately. I was not able to extract and repair the glued in resistor, but I was able to shunt it to get the set working again. I will have to find a more permanent solution, however. In the past, I would have looked for a replacement tube socket / high voltage tube holder. This part is impossible to find these days. I may have to resort to 3D printing it, keeping 17KV of anode voltage in mind, and make a 1.4 Ohm wire wound resistor.

Chester electronics had some HV socket cups of different sizes a while ago (I don't visit frequently) and I grabbed a couple for good old Justin-Case.
They may still have something that would work.

It's good to see an Austrian set in working condition in the US :thmbsp:
Otherwise I cannot believe finding a DY87 HV rectifier socket is so difficult:scratch2:

It should look quite similar like the opened one on the pictures.