C
Chris F.
Guest
Well I went to work on this bugger, and managed to take care of the
coolant spill. Instead of spraying the board with water, I meticulously
cleaned it by hand, removing many ICs and other components in order to clean
underneath. Eventually, I got the set to power up again and now it's
basically back to square one. With the one bad cap replaced, the convergence
is now much better, but the HV is still way too high. After several hours of
troubleshooting, I now strongly suspect that the big HV bleeder resistor may
be the culprit. The B+ stays at a solid 135V, from a line input of about
70VAC and up. Obviously the set is indeed regulating properly. The HV
bleeder also has a thin lead which supplies a reference voltage to the HV
shutdown circuit. A bad bleeder, and hence a lack of that reference voltage,
would explain why this circuit is not functioning. Part number is
1-453-099-11, a supplier tells me it was discontinued several years ago, so
obviously some kind of sub job would be needed to replace it.
So what do you think? Is there any way I can test the bleeder resistor,
and if so, what value(s) should it read?
As for the lack of chroma, to be honest, the picture quality is so poor
(due to the caked-on film of coolant on the CRT surfaces) that I really
can't tell if the video is normal or not.
Also, I cannot figure out how to clean the CRT and lens surfaces, on the
blue CRT which I now have apart. The coolant formed a hard white film, which
so far has defied acetone, methanol, and Windex. What else could I use to
remove it?
A good winter project, for sure....
coolant spill. Instead of spraying the board with water, I meticulously
cleaned it by hand, removing many ICs and other components in order to clean
underneath. Eventually, I got the set to power up again and now it's
basically back to square one. With the one bad cap replaced, the convergence
is now much better, but the HV is still way too high. After several hours of
troubleshooting, I now strongly suspect that the big HV bleeder resistor may
be the culprit. The B+ stays at a solid 135V, from a line input of about
70VAC and up. Obviously the set is indeed regulating properly. The HV
bleeder also has a thin lead which supplies a reference voltage to the HV
shutdown circuit. A bad bleeder, and hence a lack of that reference voltage,
would explain why this circuit is not functioning. Part number is
1-453-099-11, a supplier tells me it was discontinued several years ago, so
obviously some kind of sub job would be needed to replace it.
So what do you think? Is there any way I can test the bleeder resistor,
and if so, what value(s) should it read?
As for the lack of chroma, to be honest, the picture quality is so poor
(due to the caked-on film of coolant on the CRT surfaces) that I really
can't tell if the video is normal or not.
Also, I cannot figure out how to clean the CRT and lens surfaces, on the
blue CRT which I now have apart. The coolant formed a hard white film, which
so far has defied acetone, methanol, and Windex. What else could I use to
remove it?
A good winter project, for sure....