Looks normal, all my 5151's have those lines, but the question is, why would you turn the brightness all the way up? It's supposed to be set to pretty low so the green text is displayed on the black background without any halo effect on the letters.

edit: That being said, how long does it take for the picture to appear on screen? It kinda depends on that if you need to change the caps, but in any case I would still swap at least some of the major ones from the PSU board as it's just future proofing.

Exactly, that's the retrace line and always visible if you turn the brightness all the way up.

Turn the brightness down and adjust the contrast, the monitor is probably just fine.

The retrace lines appear before anything else on the screen, when I turn the brightness up from 0 the lines are the first thing I see, no matter what the contrast is set to.
I can start to see the lines from about 5 seconds after the monitor turns on.
Could this be a problem with the MDA card instead?

Could you post best possible picture of the monitor you can get, with something in the background (text, program)? All can I see now are retrace lines, due to CRT being overbright.

Here is a video I took of turning the brightness from 0 to max, there should be a C prompt with some text at the top. I have also tried turning the brightness so I can just about see the retrace lines, and I have left the monitor like that for 10 minutes, but after that still only the retrace lines were visible.

https://youtu.be/5NWc055Zmwc

The monitor in the video is connected to the MDA card in my 286, which has a Video 7 VEGA VGA card as the primary video card, and I have run mode mono to switch it to the 5151. I get the same problem with this MDA card in my 486, with the bios configured to use it as the primary output.

Well, all I can tell is that the brightness is too high once the background starts to get brighter (i.e. no longer being black).

Does the contrast knob do anything? Could be that this one is broken, which would lead to exactly that behaviour.

Before messing with the monitor however, I'd recommend testing with a second MDA/Hercules card.

The contrast knob feels like it is turning the potentiometer behind it, and it turns smoothly, but I can't see any changes on the screen when I turn it.

I only have the one MDA card and my computer refuses to boot when I set up this card to start as a MDA card, is there any other way to get something to display on the screen?

Chances are that your G2 (screen) voltage is too high, usually the G2/Screen is set by a potentiometer on the back of the flyback transformer (at least on "late" CRTs), on the 5151, there is a sub-brightness potentiometer somewhere on the board where the flyback sits (VR502)

Here is a service manual for the 5151, if that helps: http://classiccomputers.info/down/monitors/Sa … ts_IBM_5151.pdf

Check the constrast knob using an ohm-meter, also check the soldering points. Could be that it's stuck at the lowest constrast.

don't mess with the sub-brightness until you can figure out why the contrast knob isn't working - that's your problem

According to the service manual, you have to clean the contrast pot, when contrast control is lost, so check it with a MM like derSammler stated. If pot is OK and there are no cracked solder joints, inspect the video amp. section.

Check TR20 (2sc2229 or 2sc1921) on the neck board and also TR19 (2n3904.) See if the PCB looks dark where the transistors are. Wiggle them around to see if the joints are okay. Turn on the monitor and see if they get really hot. Finally, check the voltages when the monitor is running because the transistors will sometimes look fine when you test them out of circuit with a multimeter. Or just replace them if you feel uncomfortable doing that; they should be cheap.

I hope it's something that simple. Those are really cool monitors.

Hi, I have the same problem with my 5151. Has a solution been found in the end? I would like to bring my beautiful 5151 back to life, thanks.

Hello again, as an update I would like to inform you that I have solved the problem by replacing the integrated IC201, this is the SN7406 used as a video buffer (inverted). I hope this tip will be helpful. The diagnosis was made by analyzing the output pin (8) on which there was no signal (the input pin is 9). Cheers.

marminsky wrote on 2020-04-28, 15:05:

Hello again, as an update I would like to inform you that I have solved the problem by replacing the integrated IC201, this is the SN7406 used as a video buffer (inverted). I hope this tip will be helpful. The diagnosis was made by analyzing the output pin (8) on which there was no signal (the input pin is 9). Cheers.

This also fixed my monitor, I used a SN7406N as the replacement IC. Thanks to everyone who helped.