QNIC 2500 Monitor in Neo "Big Red" -- no picture

aclbandit

Another Striker
Joined
Aug 10, 2009
Posts
315
Hello, folks.

It's been around a year, but I'm starting work on my machines again.

Turned on my Neo after it had been off for several months. Initially, the red was out entirely (just blue and green present). I knew that would be something to fix, so I turned it off and planned to work on it.

When I turned it on again to adjust red pots (just in case), the red was present again for no apparent reason.

I played Garou for a bit. After about ten minutes, the screen started to dim, eventually turning entirely black.

Now, when turned on, the monitor doesn't light up.

The neckboard *appears* to be lit.

I replaced the fuse (with a really old, but still unused fuse), but no dice.

I have a multimeter, but I'm no expert; what shall I try first?
 

Dion

Known Scammer, NeoGeoFreak Co-Founder
Joined
Aug 24, 2000
Posts
2,070
First thing I would say is to pull the chassis and look for cold solder. The intermittent color issues leads me there first. Could also be the reason for the shutdown if the VR legs aren't making good contact.
 

aclbandit

Another Striker
Joined
Aug 10, 2009
Posts
315
Gotcha. I can do that.

It's been recapped, but it was my first. Looking at it again, years later, it wasn't the best job -- cold solder is a distinct possibility.

Forgive my ignorance, but what's the "VR"?
 

Dion

Known Scammer, NeoGeoFreak Co-Founder
Joined
Aug 24, 2000
Posts
2,070
Voltage Regulator

If you have ever seen a tv that the screen would wobble and then cut completely off when shaken a bit, this is the reason. Most TVs with vertical collapse or that will come on but then cut right off usually have a solder issue.

Yeah, I go back and look at some of my first cap kits and wonder how the monitor ever worked afterwards. Rework all of your solder and then retest. Reflow all of the header pins regardless. Every connector on the chassis and neckboard.
 
Last edited:

aclbandit

Another Striker
Joined
Aug 10, 2009
Posts
315
Joints resoldered, but no dice. The neck doesn't appear to be lighting up at all.

I'm thinking I may contact Bob Roberts about a flyback. I replaced the caps and that fixed my issues the first time, but I'm pretty sure the flyback is still the original.

That sound reasonable, or am I playing in the wrong ball park?
 

aclbandit

Another Striker
Joined
Aug 10, 2009
Posts
315
So, I replaced the flyback, but no change.

I tried removing the fuse, and one of the ends came off during removal -- looks like the "old but unused" fuse was past its end-of-life.

After replacing the fuse and turning on the monitor, there's a brief bright flash as the fuse blew. So, something is blowing fuses in the thing.

I tried a different power supply (known-working) with a new fuse, and that one blew also.

Could the "fading out" have been a slow-blow fuse or something? Where should I go from here?
 

aclbandit

Another Striker
Joined
Aug 10, 2009
Posts
315
Got it!

This had been my first soldering/recap experience, so it's awful (I have since gotten to be *much* more proficient than the shit job in this chassis). I noticed a trace that had come up (I don't even know how any person could have managed, but I did, somehow), and it looks like it had finally broken.

I repaired the trace (properly), replaced the fuse, and fired it up. Voila! I have picture.

After that, I put the original flyback back into the machine (the replacement's geometry just wasn't exactly right).

On to brighter and better things!



The red color is still missing, which doesn't surprise me. I did note that it looks like the red drive and red cutoff pots on the neckboard look like they've been bent before. The solder joints seem solid, but I've not dealt with potentiometers as a component before. Are those especially fragile components? Should I just snag some new ones and see if they fix the issue?

EDIT: Screenshot of colorbars:
 
Last edited:
Top