Author Topic: Repairing a video monitor in an IBM 3279 terminal  (Read 6473 times)

0 Members and 1 Guest are viewing this topic.

Offline inse

  • Frequent Contributor
  • **
  • Posts: 666
  • Country: de
Re: Repairing a video monitor in an IBM 3279 terminal
« Reply #25 on: March 21, 2024, 05:02:31 pm »
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 …
 

Offline audiotubes

  • Regular Contributor
  • *
  • Posts: 176
  • Country: cz
Re: Repairing a video monitor in an IBM 3279 terminal
« Reply #26 on: March 21, 2024, 09:51:36 pm »
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!
I have taken apart more gear than many people. But I have put less gear back together than most people. So there is still room for improvement.
 
The following users thanked this post: jmaynard

Offline jmaynardTopic starter

  • Contributor
  • Posts: 11
  • Country: us
Re: Repairing a video monitor in an IBM 3279 terminal
« Reply #27 on: March 22, 2024, 03:12:52 am »
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...
 

Offline jmaynardTopic starter

  • Contributor
  • Posts: 11
  • Country: us
Re: Repairing a video monitor in an IBM 3279 terminal
« Reply #28 on: March 23, 2024, 02:31:20 am »
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.
 

Offline jmaynardTopic starter

  • Contributor
  • Posts: 11
  • Country: us
Re: Repairing a video monitor in an IBM 3279 terminal
« Reply #29 on: May 27, 2024, 01:01:59 am »
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!
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf