K7000 Intermittent Red FIXED

nerdygrrl

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So I have read most of the threads on here re missing red, but just wanted to ask some things here based on my symptoms to try and narrow things down a bit.

I picked up a Neo Geo w/K7000. When I fired it up the red was a low/missing I gave the pot a little turn from side to side and it came back on and I had no problems for months until I adjusted the neckboard again.

I just assumed the pots were dirty and went ahead and replaced them all with new pots to avoid the issues that arise with these. I just rebuilt the chassis (caps,HOT, fly..) when I did that I ordered up a new transistor for the red just as a precaution because they seem prone to failure.

With everything installed, I fired up the monitor, no red. Turned it off, turned it back on and boom red. Ran it for ten minutes as I was trying to get everything adjusted and the red disappeared again after several minutes.

While I originally thought this was a dirty pot or bad solder joint on the pot, I feel like what I have done has ruled that out.

The fact that it is intermittent seems to rule out a bad trace or transistor.

I've heard that a bad tube can cause this, but I am not sure what the symptoms would be. This seems to go in and out.

Any thoughts?
 
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I didn't see any difference. I am going to reflow that for good measure later today though.

after that check continuity from the input header back to the game pcb to make sure the wire and connections are good too.
 
To test the tube, do you have a rejuvenator?

If so, can you test the red gun to see how strong it is?
 
after that check continuity from the input header back to the game pcb to make sure the wire and connections are good too.

Thanks. It just seems odd that it will be ok, go out and then come back without anything being touched or moved

To test the tube, do you have a rejuvenator?

If so, can you test the red gun to see how strong it is?

I don't. What would the symptoms be of a failing or weak gun? When the red is on, it's is on and is bright.
 
Reflowed all of the pins and voila. I should have done that before posting, but the way it was manifesting didn't seem like a faulty pin joint.

Anyway, many thanks for the input and help. It feels nice to get another cap kit and rebuild under my belt.
 
like it or not ... :)

nicolas-cage-facepalm1.gif
 
This place is really fantastic. I am always grateful for the input and tips.

More than likely my primary issue was with the pots/neck and the cracked joint or whatever was a secondary issue that came about after the fact.

Now about this convergence...
 
This place is really fantastic. I am always grateful for the input and tips.

More than likely my primary issue was with the pots/neck and the cracked joint or whatever was a secondary issue that came about after the fact.

Now about this convergence...

I'm sorry I didn't answer you the other day, I don't even remember what you asked.. if this was it or not. the ceramic (white) pots on the K7000s are incredibly fragile, so naturally a first place to look. the next common thing is the transistors will break a leg off -- in my estimation its cause they have no heatsinks to keep them from moving around, so they get twisted around and bent a lot. the last thing, which isn't as common but can happen, is they'll pop a solder pad off the trace (much like the Ux000/K7x00).

convergence is an artform I haven't yet mastered. read the K7000 manual and there should be instructions in there.
 
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