View Single Post
Old 14th Oct 2021, 10:26 pm   #18
AdrianH
Octode
 
AdrianH's Avatar
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 1,060
Default Re: 5FP7 project starting with the focusing coil.

Hello Graham. I am going to try using a version of the circuit provided in post #14.

I spent a few hours in the garage/workshop making a small chassis and drilling holes for the valve sockets. I will admit that I am initially trying ECC82 & EL91 valve, just because I have the EL91's. I think I should be OK within the valve ratings it does fine in the home made TV.

I am not sure if the SSTV unit in the 1970 RSGB book was all valve or just the HT unit?

I am pondering if I can scan the full width of the tube with valves rather than using a transistorised push pull circuit. Just not sure if with a very slow frame rate, 6Hz, I will get the required negative going flyback in the coils to take the trace to the left of centre? With a transistorised and split power rails it would be easier. Just something for me to ponder.

I used my little component tester TC1 on the LOPT I have, and measured a whopping 7 Henry from the overwind to the other end of the coil. A lot higher than I expected? It is getting 20+mA passed through it to get rid of any moisture that may be in it.

Adrian
__________________
Asking questions and learning, or trying to!
Youtube EF91Valve
AdrianH is offline