Repairing a video monitor in an IBM 3279 terminal

[inse]

Ok, but after all it’s just a ASCII terminal, no TV or hires monitor for image processing.
As long as text is readable, it should be fine, I would say …

[audiotubes]

Ok, but after all it’s just a ASCII terminal, no TV or hires monitor for image processing.
As long as text is readable, it should be fine, I would say …

Not ASCII! EBCDIC!

[jmaynard]

Did some measuring with my handy dandy Scopemeter...and got some weird readings: G2 voltage is way low, and the waveform on the green cathode is 14 volts P-P while the other two are about 20. That would explain why the green is dim. May not be a weak tube after all. Then again...

[jmaynard]

Pulled the plastic shields off the monitor. Found the video amplifier hiding int he bottom...and the drive controls. Saw that the green drive was turned down relative to the red and blue. Turned it back up, and got the green visible. Yay! The voltages are still funny, though. I'm not doing to dink with them till I get a much better understanding of what the controls do.

[jmaynard]

Just to wrap this up: Turns out that the only thing it needed once I got it to the poin of being able to see all three colors was to adjust the grid 1 and screen controls. Once I did that, it brightened up just fine.

I've now got another with the same monitor in it (or nearly so), with what seems to be a cracked voltage tripler in it, but that's a problem for another time.

Thank you all for the help!