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NEC Multisync II - Blank white screen?

Ozzuneoj

Experienced Member
Joined
Nov 16, 2015
Messages
185
Location
PA, USA
I drove a couple hours to pick up this Multisync II a few weeks back... I was so happy to find one locally after a bad experience last year where I received a comparable "multisync" capable Sony display which was sadly damaged in shipping.

It was advertised as working and would power on, but the seller no longer had any old PCs or the requisite cable to test it. For $30 it was still well worth it! :)

I checked out the internals and it wasn't real clean but I didn't notice any burnt smell\components or exploded\leaking capacitors, so I figured it'd be safe to test it out at least. I only have one straight-through DE9 serial cable (verified with a DMM to be straight-through on all pins), so I used that to try the monitor on two different PCs, but both give the same result. The first was my GRiDcase 1530 with CGA output. The second was my IBM 5150 with an Everex EV-659 card currently configured for 16-color EGA output to my 5153 display.

When the monitor is connected to nothing and is powered on it will give a white-ish screen with a pretty strong flicker... probably 50Hz.

When I connect it to a PC I get the same white-ish screen but with almost no flicker.

Either way, there is no signal and none of the switches or adjustments on the monitor seem to change the picture at all other than a slight change in brightness with I turn the brightness dial. I have tried the auto and manual modes and I have compared pinouts for CGA\EGA and this monitor and it honestly looks like everything should just work with a straight through serial cable unless I'm trying to connect to a 15pin VGA display which would require a converter of some kind.

Is this likely to be a cable\signal issue? Or is there a common failure point within the monitor that might cause a complete lack of signal? I find it interesting that the display's flicker changes when it is connected to a PC, but I don't know enough to say if that's important or not.

If anyone has any suggestions, please let me know! I can provide pictures if necessary.

EDIT: Also, as secondary question... is it possible to use the Multisync II with computers or game consoles that use a single RCA jack for composite video output? I'm thinking the answer is "no" without some kind of converter, but I'm not sure.
 
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It's a "II" or a IIA/2A? I had the latter back in the early 90's, and it was VGA only. Not sure why they called that a "multisync"
It's a Multisync II Model JC-1402HMA, definitely supports CGA, EGA, VGA, etc.
The manual is on MinusZeroDegrees: http://www.minuszerodegrees.net/manuals.htm#NEC

It has some pretty good troubleshooting flow charts you might check out.
Thanks! I already had the manual. I figured whatever was wrong would be something they wouldn't have anticipated 35 years ago, but I'm checking it out now.

To be honest, that section is a bit over my head because I don't know a lot of the terminology. Definitely seems like it was written for an experienced CRT tech. I have done a little work in CRTs (replaced some caps in my 5153), but I'm not good enough with circuits to diagnose this myself without a bit more direction. I'm also not sure if it's just the cable or something else.
 
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The II should be mostly plug and play with CGA and EGA (VGA needs an adapter). You clearly have high voltage, so at least the flyback is working. The DB-9 can be tempermental on them if I recall. Make sure the plug isn't loose and check the solder points.
 
The II should be mostly plug and play with CGA and EGA (VGA needs an adapter). You clearly have high voltage, so at least the flyback is working. The DB-9 can be tempermental on them if I recall. Make sure the plug isn't loose and check the solder points.
Thanks. The DE-9 connector seems pretty solid on this one, but I have read about some people having color issues. The PCB it mounts to seems to be pretty well buried in layers of metal shielding, so I'm not sure if I'll be able to get in to look at the solder joints on the connector without a bunch of messing around.

It is worth noting that someone had apparently poked some holes in the plastic chassis to reveal the adjustment pots on the left side of the monitor. It looks like 5 pots are visible through the holes (three right next to each other and then two others a few inches away). I'm trying to figure out what these are for right now. Seems odd that someone would monkey with something to the point that it would make it not display a picture at all... more likely they did this to adjust the picture when it was working, otherwise why would they need to mess with picture adjustments while it was assembled? If it was not showing a picture at all they would have just tinkered with the adjustments with the cover off to see if it made any difference... unless they were super scared about being electrocuted I guess... haha
 
The adjustments on the flyback are for focus and screen which I've had to tweak once. I have never had to touch any of the other pots on the board.
 
Okay, I was able to get into this thing pretty easily thanks to this video:

It doesn't give a lot of detail as far as disassembly goes, but it's pretty straight forward. You just have to take the whole "module" out the right side (looking at the back of the monitor), so there are a couple of metal panels that need to be unscrewed to make a clear path, including the large one that runs up that whole side of the chassis. There are hooks on the bottom metal casing of the module as well as on the bottom of the chassis so you need to lift it straight up to clear the clips while being careful not to put pressure on the PCB that connects to the neck of the CRT. It seemed a little sketchy at first but it was not what I'd call difficult once I knew what was going on. Also, you'll need to disconnect some small connectors that are plugged into the top of the module as you're pulling it out the right side. Take pictures while you're doing it. Also, there are some well hidden screws that hold the shielding on, including the screws that run directly through the DE-9 connector into the shielding below.

I'm happy to report that there isn't any noticeable damage to the solder joints or anything else on the PCBs. Using a magnifier I see what looks like a faint line around the solder joints in a few places, including a few pins on the DE-9... but they don't look broken. Still, there's a chance these joints could be at fault, so I'll try to touch as many of these up as I can.

Are there any caps on these boards that are common failure points? I probably have some replacements on hand.

I don't want to go too crazy with this though because I know that every time you take a soldering iron to a board you're taking a risk. I am not a "replace all caps over 10 years old" kind of guy at all.
 
Look for the cap poop (leaked electrolyte), or bulging caps first. Also look for hot spots on the pcb where its discolored. If there is a cap in that area, replace it. Keep an eye on temp ratings of the caps, try to go with a higher max temp rating if possible.
 
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Look for the cap poop (leaked electrolyte), or bulging caps first.
I'll be honest, I've seen a ton of caps in various devices with epoxy on, under or on top of them, and I've seen boards with lots of excess flux, but I've only seen leaked electrolyte that looked like this:

And those were only ever on devices from the cap plague era as well as some very crappy motherboards with generic caps from the late 90s.

What would leaked electrolyte look like in a device like this?

As a rule I always check for Rifa X caps before powering anything on from the 80s, I know to be aware of possible tantalum failures (explosive, short or open) and I'm always suspect of poorly made early surface-mount electrolytic caps, but I very rarely have to deal with out-right failures of through-hole aluminum electrolytics in older devices. I've searched for good pictures of what to look for, but it is generally just people mistaking epoxy\glue for leaked electrolyte. If you can show me some examples of what is definitely leaking electrolyte I'd appreciate it.

EDIT: I haven't noticed any hot spots or signs of other issues on the PCBs I have pulled out either.

I just checked the solder joints on the DE-9 with my DMM and they hold continuity even when moving the connector slightly, so I don't think I need to bother reflowing them.
 
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Does the monitor show a visible flicker when your input source turns on? As in, does the monitor try to sync to the video source? If so, at least some of the signals off the DE-9 are making it into the monitor. Next step would be to get out a scope and start seeing how far the input signal makes it into the monitor.

I've had bad through-hole caps in 1980s electronics fail. My stereo receiver had a few that didn't have visible signs of leakage. They were pretty baked from heat over the years.
 
I remember using one of these with a composite input to the green and enabling sync on green. (I dragged it up on the roof to fine tune my cband sat dish)

Quick and dirty single wire input for testing? But this might have been an original multisync.
 
Does the monitor show a visible flicker when your input source turns on? As in, does the monitor try to sync to the video source? If so, at least some of the signals off the DE-9 are making it into the monitor. Next step would be to get out a scope and start seeing how far the input signal makes it into the monitor.
Ah... wish I'd have thought about that before I disassembled it. I will have to put it back together to do some more testing I think.

I don't really have a functional scope (just an old Techtronics that hasn't worked in a few years), and I've never really learned how to use one.

I was really hoping that someone else would have had a similar problem with one of these and would know of common failure points. When I had color problems with my 5153 there were several posts and even a youtube video explaining what to replace to fix it.

I've never had any training with circuits or electronics in general, so I'm basically just self-taught (along with videos and forums) at this point. I'm okay with soldering and I have the tools, but the knowledge to diagnose is pretty lacking. :D
 
The point of using a scope is to probe the path a video signal is taking. Its a good way to narrow down an area with a possible bad component. One thing I would try is fiddling with the screen pot on the flyback. You could have a very very dim raster and not realize it. If its a high hours unit, its possible that the tube is tired.
 
He said he gets a white screen on power up, implying raster.
This is a "good" thing right? The other two CGA\EGA monitors I have used (IBM 5153 and a "Sysdyne!") have a similar white screen when turned on with no signal.

I just reassembled it (surprisingly easy) so I can try to narrow down what it's doing a bit better.
 
Okay, when the monitor is connected to my IBM and the PC is off the monitor will show a white screen with a fairly low refresh rate "flicker". As soon as I switch the PC on the monitor will flash once with a horizontal line briefly, then after a few seconds it seems to lock onto a refresh cycle and the flicker goes away, leaving a solid white flicker-free display.

I notice now that if I play with the adjustments (H-Size, etc.) on the front it does make a slight difference and sometimes will cause the top and bottom of the screen to darken... so the controls are doing something. So, it seems the monitor is syncing, and the CRT is functioning (it's white), but the signal is not coming through properly. No matter how I adjust brightness or contrast I don't see any hint of text or movement on the screen... just solid white.
 
I only have the original Multisync, connector there is straight thru for digital. Do you have switches on the back for digital/analogue. Think you also set it to 16 colors.
 
mR_Slug, your avatar couldn't have come at a better time...

Good news everyone!

I fiddled with the adjustment pots that were exposed on the left side of the monitor while it was on and eventually saw a blinking cursor! After playing with more adjustments I can now read text at the command prompt clearly. The strange thing is, it's sort of "inverted", as in the text appears black with a dark greenish background. Also, there is an angled shadow on the right side of the display as if something is misaligned, but the text is perfectly level horizontally.

So, this is definitely progress! I have a feeling that someone monkeyed with the adjustment pots and goofed a bunch of things up, which is probably an indicator that there is going to be some other underlying flaw once I get it adjusted back to where it should be... but at least I'm on my way now.

Any suggestions on what may cause these symptoms? I can post pictures later after dinner.
 
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.
 
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