K4900 Cracked Chassis Trace Help

Torin

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I received a K4900 that was cracked during shipping. At first, I couldn't get any neck glow and then I fixed a broken trace and now can get neck glow with only a thin line running across the monitor. The monitor is mounted horizontally and the line runs straight across the middle of the screen (Vertical deflection problem)

I have previously repaired a cracked neckboard by putting jumpers across all of the broken traces. However, this one is more difficult to track down the broken traces and I was hoping you could help me figure out what I need to do. Here are two pictures with the crack (it runs from the bottom where the yellow jumper is up to the hole in the upper left hand side).

The first picture shows it with my first jumper, the second shows what I think should be jumpered. Any other ideas for jumpers is much appreciated.
 

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I'm not really sure I understand the question? Yes, you can patch the traces with wire as you've begun doing. Just follow the traces that go through the crack, reconnect them with wire. Another option is to simply file away the solder mask near the break, and bridge the traces right at the crack with solder and some bare wire.

If you're unsure of where a trace goes, or are having a hard time following it through the board, you can use your meter to find which solder pad is connected to the broken trace.

-Ian
 
Ok, thanks for the replies. One question I have is in the second picture, I'm not sure which leg of the resistor Q303 I should solder the jumper to. I think it's the Collector but i want to be sure. Is there a way for me to determine this?

EDIT: Nevermind, I think I'll just bridge the broken trace like suggested above.
 
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Ah. My bad, different animal. Hm...maybe shoot Buffett a PM, he's got a junk 4900 I just sent him - maybe you can scavange some parts from him? Or he could assist in taking a closer look at your pics.
 
Ah. My bad, different animal. Hm...maybe shoot Buffett a PM, he's got a junk 4900 I just sent him - maybe you can scavange some parts from him? Or he could assist in taking a closer look at your pics.

Cool, thank you. I am going to try to repair it tonight. I have a 4900 in a Robotron I can take out and compare if needed. I will try to bridge the broken traces before I do that though. Buffett is always a huge help and I might seek help if all else fails.
 
keep at it you will concur it.

i know it's hard to find those cracked traces i spent a good wile on this one till i found all of them.
there are allot in the same area as the one your working on.

http://forums.arcade-museum.com/showthread.php?t=209526

i had to flex the board allot and listen to it very closely to hear the grind/popping that the cracks were making. and allot of flash light under the chassis recon as well.

the chassis is solid and good to go after all the hard work.

Peace
Buffett
 
Huge help as always Buffett. I see one immediately from your pics that I didn't notice that I need to do on mine. Can't wait to get home to get started. I can't believe you did 17 jumpers! I'm hoping mine is like 4 :)

I will post my results.


keep at it you will concur it.

i know it's hard to find those cracked traces i spent a good wile on this one till i found all of them.
there are allot in the same area as the one your working on.

http://forums.arcade-museum.com/showthread.php?t=209526

i had to flex the board allot and listen to it very closely to hear the grind/popping that the cracks were making. and allot of flash light under the chassis recon as well.

the chassis is solid and good to go after all the hard work.

Peace
Buffett
 
Ok, well after many inspections/jumpers/tests, I finally fixed my vertical collapse. Now, I have a sync problem. Here's a picture of what it looks like. I adjusted the pots but it doesn't sync. I can get it to slow down the up/down scrolling but the left/right is fast and I can't find where to adjust that. I think I still have a chassis issue. Any ideas on where to look for the sync prob? The game is Joust and it works with another monitor. The pinout is the same as the 4900 in my Robotron game and so I can see that my video cable has the same orientation. Thanks again.
 

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So, after many adjustments, I have a good image of the game but it is still not locking in vertically or horizontally. Slow rolls both ways. The pinouts on the harness for Joust and robotron are identical and they are both using 4900's with the same pinout and so I don't want to move the sync pins around unless necessary.

Any ideas on how to get this monitor to sync? I have checked the traces around C315 and reflowed much of the board already. The only thing I can think of is maybe Q301 went bad. Do I test this by removing it or can I test it in circuit? I could still be missing a trace or jumper from the original crack, I guess.

So close...I can't turn back now.
 
Well, just to rule it out, I switched the sync pins and it is doing the exact same thing. Crooked rolling picture. Any ideas on what to check for sync issues? When testing resistor Q301, do I have to pull it to get a good reading or can I test it in circuit. I appreciate any help or ideas.
 
Bumping this thread. I am out of ideas and have almost reached my wits end. Here is a picture of what it is doing. It is just scrolling left to right and slightly up and the picture is slightly crooked. I have tested B+ and it is 128.5. I have reflowed almost the entire board by now. I have changed the sync wires to the monitor from the game. I have jumpered all of the broken traces I could find from the crack. The pots affect the roll but I can't get it to completely sync. I appreciate any help you all might have.
 

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have you subbed out IC3 yet to verify it is good or bad.

other wise it still may have a cracked trace.

Peace
Buffett
 
I have not done that yet. Do you know where I can find the values for IC301 and Q301 etc...? I've looked at the manual and can find the expected voltages but not their values to go and buy replacements.
 
Made some progress and found another broken trace. Fixed it and now I can sync the picture! However, I have a pretty good screen curl. The board has been capped. The sync is still pretty hard to lock in. When I push on the chassis, the screen will start rolling again until I let up. The picture is pretty jumpy even when not rolling.

It still seems like it could still be due to the crack in the chassis.

Where else should I look for a screen curl like this? It is almost as if the picture is tilted slightly to the left. Could this be a yoke issue? Here are some pics. Thanks for any ideas.
 

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yes a cocked pic is usually from a yoke that move.

if you push on the chassis and it rolls you have more broke traces.

Peace
Buffett
 
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