modessitt
Volunteer: Encyclopedia Submission Moderator
Got two problem chassis:
1) B+ is at 22.8vdc. The 180-ohm pot gets smoking hot. I've swapped out IC601, IC401, the 180-ohm, the one below it, the current limiter, the HOT, the flyback, reflowed every single thing, and VR451, and still get this issue. The B+ pot is measuring properly, but I haven't tried replacing it yet.
2) B+ is at 140.1vdc. Reflowed everything. Swapped all the same parts as above. Tried turning both the B+ pot and VR451 counter-clockwise, but that didn't make any change.
Both monitors were working prior to coming to me. The owner installed a cap kit on one (#2), and it died not long after. The other (#1) had a horizontal hold issue, and was dead after the cap kit.
Any ideas? I've been checking trace continuity but I'm not finding any issues.
Here's something of interest on #1. I have a working 20EZ to compare to, and when I use the diode test and measure the filter cap (black on negative lead) I can watch the reading climb as the cap charges. That's normal. On #1, it only climbs to about .336 and stops. If I remove the fuse, then it climbs all the way like it should. I've traced it as far as the flyback pin, and if I cut that trace right before the flyback pin, then it charges like it should. Obviously something on this chassis is not working like it does on the working one....
1) B+ is at 22.8vdc. The 180-ohm pot gets smoking hot. I've swapped out IC601, IC401, the 180-ohm, the one below it, the current limiter, the HOT, the flyback, reflowed every single thing, and VR451, and still get this issue. The B+ pot is measuring properly, but I haven't tried replacing it yet.
2) B+ is at 140.1vdc. Reflowed everything. Swapped all the same parts as above. Tried turning both the B+ pot and VR451 counter-clockwise, but that didn't make any change.
Both monitors were working prior to coming to me. The owner installed a cap kit on one (#2), and it died not long after. The other (#1) had a horizontal hold issue, and was dead after the cap kit.
Any ideas? I've been checking trace continuity but I'm not finding any issues.
Here's something of interest on #1. I have a working 20EZ to compare to, and when I use the diode test and measure the filter cap (black on negative lead) I can watch the reading climb as the cap charges. That's normal. On #1, it only climbs to about .336 and stops. If I remove the fuse, then it climbs all the way like it should. I've traced it as far as the flyback pin, and if I cut that trace right before the flyback pin, then it charges like it should. Obviously something on this chassis is not working like it does on the working one....
