IBM 5151 Monochrome monitor issues

[jwhitney]

I have an IBM 5151 monochrome monitor that has not been used for many years. I cleaned it up, inside and out, and turned it on using the B&W/Parallel card in my IBM 5150 PC. It worked, but the 80x24 character image only took up 60% of the screen's real estate. I adjusted the V-Size control to max and it only got to about 1" from the top and bottom edge. The H-Width gets me to 3/4" from right and left side.

Any ideas?

 

[Chuck(G)]

Yup. Get your voltmeter out and the schematic for the monitor (available online) and start checking power supply voltages. Probably a bad capacitor.

Another possibility, depending on your handling of monitor, is that the deflection yoke on the CRT neck has loosed and slid toward the back of the case. That one's easy--just slide it toward the screen face and maybe use a drop of paint of lacquer between the yoke and the neck to make sure it doesn't happen again.

 

[modem7]

For comparison purposes, the borders on my 5151 are: left = 1", right = 1/2", top = 1/2", bottom = 1/2"
Looks like mine needs to be shifted to the left a little.
I doudbt that the size adjustments in my 5151 are at their maximum setting.

Schematic and waveforms are in the document at http://members.dodo.com.au/~slappanel555/manuals/Sams_5151_VDU.pdf

 

[jwhitney]

Thank you. I'll have to check for faulty voltages. - JW

 

[RetroHacker_]

Agreed, probably a bad capacitor.

Also remember that you're not going to get the text all the way to the very edges. At least, probably not. Remember that this era of monitor was not meant to go from absolute edge to edge, there should be a half inch gap (or slightly more) between the bezel of the monitor and the edges of the text.

Even graphic monitors didn't go to the absolute edges of the screen until later on.

-Ian