Main > Monitor/Video Forum
China MIN DONG TV-MD 14/22 repair
perjmolsen:
Hi :cheers:
I can not remember, but i think that i had it connected.
I have now disconnected the yoke and also the bulb and got this reading
princess prin prin:
I think pins 9, 10, 11, 12 are the primary winding of the flyback. 9 ultimately goes to the 8-pin header to the neckboard so it's likely to be the video B+ (200V supply for the RGB amps), 10 is the B+ and either 11 or 12 is the HOT collector. There should be a very low resistance (or continuity) across each other and very high or infinite resistance with all the other flyback pins. Once this is confirmed, desolder pin 9 and resolder pins 10, 11, 12 and do the lightbulb test on the HOT collector with the chassis disconnected from the tube/yoke. If it fails try it again after desoldering one by one C20 and the two big polypropylene caps conncted to it (those just below the yoke header). At somepoint it cannot fail as there's nothing else connected to that line.
perjmolsen:
--- Quote from: princess prin prin on January 16, 2019, 10:12:55 am ---I think pins 9, 10, 11, 12 are the primary winding of the flyback. 9 ultimately goes to the 8-pin header to the neckboard so it's likely to be the video B+ (200V supply for the RGB amps), 10 is the B+ and either 11 or 12 is the HOT collector. There should be a very low resistance (or continuity) across each other and very high or infinite resistance with all the other flyback pins. Once this is confirmed, desolder pin 9 and resolder pins 10, 11, 12 and do the lightbulb test on the HOT collector with the chassis disconnected from the tube/yoke. If it fails try it again after desoldering one by one C20 and the two big polypropylene caps conncted to it (those just below the yoke header). At somepoint it cannot fail as there's nothing else connected to that line.
--- End quote ---
Hi
Sorry for the delay this time :) And thanks for your tips Princess prin prin, I have made some progress (i think) ;D
Test conditions: HOT is out, Jumper is lifted and nothing connected to the chassis.
Started testing de-soldering pins at the flyback except the input at pin 10 and also the ground pins where connected.
I am loosing my 113V when i connect the 1 pin on the flyback, all other legs connected, there is 113V at HOT middle pad.
If I look at the other side where pin 1 is connected there is a big CAP - It might be shorted?
Trying to pull that out and see what reading i get from it
perjmolsen:
Update
Tested the big cap at pin1 - an 100uf 200V cap.
It does not seem to be bad.
I measure it to 90 uf ESR 0.43 ohm
perjmolsen:
Hmm...
Put in a new 100uf 200V cap - soldered the pin1 at flyback to pcb
Just light for a second... ???
Again if i remove the solder at pin1 - my volts is back... why?!? :)