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NEC Multisync II - Blank white screen?

dabone said:
On your EGA card, what happens with
On the rear, the manual switch turned on (to the right), Mode to Color, and Color mode 64 (All the way to the right).
On the front, H size off, text off, text color to the right.
Click to expand...
I tried it this way as well as with the switches set to 16(IBM), grey scale and auto, and all were pretty much the same. I have been switching modes on the EGA card as well since it supports many different modes. So far, nothing has really made a noticeable difference. If I get some time tomorrow I will open up the monitor again to play with some of the pots and hopefully get the image back to somewhat normal.

Seems odd that I'm getting what looks like inverted colors on the command prompt. I will try to run some graphics tests on it as well to see what it does.
 
Here is a picture of the monitor running Checkit 3.0. I have tried adjust all of the pots on the left side of the monitor and some would change the intensity\saturation of the colors to an extent, but it's like they're just the *wrong* colors, and the *wrong* intensity.

It's almost like everything is there but is just inverted.

I'm starting to second guess myself... I am using a 9pin to 9pin serial cable with a gender changer on one end. When I beep out both ends side by side so they are facing me in the same orientation, each pin appears to be correct. So I don't think that's the case.

What would cause everything to be, seemingly, inverted?
 

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The original cable is DE9 Male on both ends wired straight thru. Pin 1 to 1, etc.
 
njroadfan said:
The original cable is DE9 Male on both ends wired straight thru. Pin 1 to 1, etc.
Click to expand...
It is probably not the cable then.

Does anyone know of any other forums or parts of this forum where I might find a bunch of people that have done repairs on these? I was thinking of asking at an Amiga site since people use old Multisyncs for those too.

With my level of knowledge I'm more likely to screw something else up since the documentation for this monitor is almost like reading another language. They use lots of technical terms but rarely use a full sentence of plain English to describe an actual issue or to explain what the various internal adjustments actually do to the picture (as opposed to speaking in terms of voltages). This is expected because most people didn't tear into these things 35 years ago without training... but not too convenient for a hobbyist like myself.
 
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I would attempt to get an analog source into the monitor and see how it behaves in terms of colors.

The text switch should change the color of text at a command prompt when in TTL mode for example, but not while in analog mode.
 
Also, from the service manual. The reason for testing analog input is to bypass the DAC for CGA/EGA video to see if its the source of the abnormal colors.

1652048116261.png
 
Thank you! I'll check that. I think I'll need to buy one of these 9 to 15 pin multisync adapters.


Amazon seems to be the best place to get one, but I'm not sure if they're cheaper elsewhere.

EDIT: Duh, nevermind, I misread it... it specifically says its NOT for old NEC Multisync displays. Derp...

I have plenty of spare VGA cables as well as a bunch of D-sub connectors. I'll just wire up my own cable to be sure the pinout is correct. I've never done it before but it shouldn't be hard.
 
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Attached is the pinouts I have on hand
 

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Okay, more developments!

I built myself a 9pin analog "Multisync" to VGA cable (just lopped the end off a VGA cable and put a DE9 end on it using mR_Slug's pinout) and it seems to do basically the same thing as the CGA\EGA cable, so my cable works! Yay!

But, that means the problem is something deeper than the EGA\CGA portion of the monitor. The colors and "brightness" seem to all be inverted. At the DOS prompt with the "brightness" and "contrast" dials turned to their maximum (clockwise), the black background is light grey and text is black. If I turn the brightness dial down (counter-clockwise) the gray background will start to turn green, then eventually black (text is no longer visible). It seems like anything that is supposed to be a medium gray is actually green.

This is with the internal adjustment pot (the one that is near the bottom-center of the monitor on the left side) adjusted full counter-clockwise to make the screen dark enough to be readable. If I turn it clockwise the screen gets very bright white and eventually shows faintly colored lines. So, it seems to have no problem producing a bright picture. There's just something entirely wrong with the colors and brightness.

Also, the picture is extremely clear. This tube likely has a ton of life left in it once the colors are sorted out. :)
 
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Just wanted to give this a small bump now that I have some time. Does anyone have any ideas as to what would cause the color problems mentioned in my previous post? It's like the colors\brightness are inverted or something, and it does this with both EGA (TTL) and VGA (analog) signals.
 
Other than spotting something obvious with a close visual inspection, I don't think there will be an easy fix here. It's probably not something you can adjust your way out of. I would attack the problem by using an oscilloscope and the service manual to trace the video signals through the circuit starting at the input jack, and ending at the CRT cathodes.

archive.org

NEC Multisync II JC-1402 Service Manual : Free Download, Borrow, and Streaming : Internet Archive

NEC Multisync II JC-1402 Service Manual
archive.org

Maybe if you try the video adjustment procedure in section 3-2 you'll find some clues if one or more controls don't behave as they should.
 
andy said:
Other than spotting something obvious with a close visual inspection, I don't think there will be an easy fix here. It's probably not something you can adjust your way out of. I would attack the problem by using an oscilloscope and the service manual to trace the video signals through the circuit starting at the input jack, and ending at the CRT cathodes.

archive.org

NEC Multisync II JC-1402 Service Manual : Free Download, Borrow, and Streaming : Internet Archive

NEC Multisync II JC-1402 Service Manual
archive.org

Maybe if you try the video adjustment procedure in section 3-2 you'll find some clues if one or more controls don't behave as they should.
Click to expand...
Thank you for the suggestions. I was afraid it would be that level of repair. For me to do that I'll have to learn how to fix my oscilloscope (it's an old Tektronix 2235 an engineer friend gave me when he moved away 10 years ago), then learn how to use it since I have never really used one before. In other words, this will be a long process, heh.

I will check out the adjustment procedure though, just in case it helps to narrow things down. I was hoping this was a common and documented failure, but that doesn't seem to be the case. Most likely the issue is that these monitors are just plain rare these days.

I had color problems with my IBM 5153 and it was a common and documented issue so it was a fairly easy fix that just involved swapping out some caps. Not the case with this one it seems. 😵
 
Have you tried cleaning all the slider switches on the monitor with Deoxit ?
The contacts on these type of switches get dirty over time and can cause
problems.

I had a similar issue with my Mitsubishi AUM-1381 monitor , the switches weren't
changing the image as they should. Cleaning with Deoxit solved the problem.
Accessing the back of the switches for cleaning can sometimes be challenging.
 
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If you haven't already, you should remove the boards related to video processing (input, interface, video, and CRT boards). Remove the metal shielding, and carefully look them over for obvious problems like leaking caps, bad soldering, overheated parts, previous repair work, and so on.

Depending on how heavily used the monitor is, it may have bad caps. An ESR meter is a great tool for checking for dried out caps. You can get a good idea for how heavily used it is by looking at how clean it is inside since the HV attracts dust only while the monitor is on.

Even with just a volt meter, you can check for a lot of things. The schematic has voltage measurements noted for many parts. I generally start by confirming that the power supply voltages are correct. Since all three colors are affected, it has to be something in common to them, which rules out a lot right there. You can safely run the monitor with the shields removed so you can make measurements.
 
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