Level42
New member
Can a black level pot make the screen look very dim ?
I am working on two 25K5515s form two HD's at the moment.
One had a HVT that went off in fireworks. Replaced it and it works again. HV is at 25 kV.
I tried increasing the Screen pot but pretty soon I get the usual greyish screen with visible retrace lines.
Since there are no other controls for brightness I figured Id check the Black Level pot which is supposed to be 2k but it measures up to 2 Megaohms between the runner and both legs, no matter what position I turn it to.
The pot also feels grindy when turning ite so it's 100% dead but I wondered if it could give this effect.
The other chassis also works but has vertical deflection problems. Its not just only a horizontal line, it incidently shows lines up and down from the horizontal line, like indeed a bad contact or a bad pot so I'll check the pots on that one too.
Checked all caps with an esr meter and replaced the bad ones.
I am working on two 25K5515s form two HD's at the moment.
One had a HVT that went off in fireworks. Replaced it and it works again. HV is at 25 kV.
I tried increasing the Screen pot but pretty soon I get the usual greyish screen with visible retrace lines.
Since there are no other controls for brightness I figured Id check the Black Level pot which is supposed to be 2k but it measures up to 2 Megaohms between the runner and both legs, no matter what position I turn it to.
The pot also feels grindy when turning ite so it's 100% dead but I wondered if it could give this effect.
The other chassis also works but has vertical deflection problems. Its not just only a horizontal line, it incidently shows lines up and down from the horizontal line, like indeed a bad contact or a bad pot so I'll check the pots on that one too.
Checked all caps with an esr meter and replaced the bad ones.
