Predicta 17" HV question

[DaveWM]

if you do need to replace it, I would pop for the film cap, the disc cap will prob be work fine, but may drift causing changes in vert height as it heats up (clearly if this is the problem).

[Phil Nelson]

I replaced that cap with the .0015/1KV ceramic that I had on hand, just to see what happened:



No magical improvement in the height, unfortunately. And you're right, it changes value when heating up. After a few minutes of play, the vertical becomes unstable and then collapses.

Mouser has 1KV micas of the right value. I presume those would be a better choice.

Phil Nelson

[DaveWM]

I would stick with a reg film cap. After you get the correct cap in, try reading the PP on pin 6. You need to find out why the PP is only 30v and not 140v.

I am sure you have checked, but I presume you are seeing the 275v on the red lead of the vert out.

check for the 400v boost on the one side of the height (if not checked already). did not see a check mark by C3A 10uf 450v

[Phil Nelson]

OK, justradios has orange drops of that value. I'll order those.

Incidentally, the series-d caps I removed were .0033, not .00033, so I'm not as crazy as I thought. They were film caps and also stable, unlike the ceramic. I'll put a pair of them back in so that I can play the set for more than 2 minutes at a time while waiting for more parts to arrive.

Edit: the 275V source is at 273V, like before. The 400V source was 400V when I checked before, now it is somewhat high at 430V (don't ask me why).

Regards,

Phil Nelson