Help me, I broke my 4900...

keithsarcade

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I picked up a Tron recently with a mostly working WG4900 inside, appears original. By mostly working, I mean that it would show just a line going up and down on cold startup, but after a tap of the cabinet or a brief warmup, the picture would come on, and looked decent. So I pulled the chassis looking for bad solder joints, which I did find some on the flyback. Patched those up and reflowed joints on the width coil, yoke pins and the 6/3 header pins for good measure. Now all I get is that bright line. I can wait for hours now and kick the game in the ass all I want, still no picture. What did I do?

The chassis appears to have new caps installed, not sure how long ago, but looks like recently. I suppose I could try a cap kit, but its just strage that patching up bad solder joints has acually made the problem worse, so I'm scratching my head with this one :confused:

Any ideas?
 

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Your problem is you have no vertical deflection. Very, very, very common on a 4900.

The vertical section is in the back of the board, and probably flexed a bit when you moved it out of the game.

The solder pads on everything back there can develop bad joints, particularly where the two vertical transistors are. Just resolder anything that gets in your way back there, and try it again. Solder solder solder, lol.

Also check those yoke pins one more time.
 
Your problem is you have no vertical deflection. Very, very, very common on a 4900.

The vertical section is in the back of the board, and probably flexed a bit when you moved it out of the game.

The solder pads on everything back there can develop bad joints, particularly where the two vertical transistors are. Just resolder anything that gets in your way back there, and try it again. Solder solder solder, lol.

Also check those yoke pins one more time.

i am so glad guys like you are here!
 
Didnt see any more bad solder joints, but I did find out theres a crack in that corner which has previously been repaired and bridged. I reflowed all solder there, expanded bridges and added a few others for good measure. Still getting nothing but that bright line.

At this point, thinking about asking around for a "hopefully" cheap repair from someone more qualified, or possibly a "chassis + cash for working chassis" deal. Anyone interested before I decide either way?
 
First, measure your vertical yoke wires (green and yellow) to see what reading you get.

I fix 4900's for $50 + parts + shipping...
 
Okay, your yoke is okay. Measure your two vertical transistors (Q302 & Q303) to see if either is bad. Also check R313...
 
You can also get vertical collapse if one of the caps in the vertical section is installed backwards, C308 or C310 I think.
 
Okay, your yoke is okay. Measure your two vertical transistors (Q302 & Q303) to see if either is bad. Also check R313...

I am measuring Ohms on these also, correct? I assume they should be getting the same reading that the yoke got?

You can also get vertical collapse if one of the caps in the vertical section is installed backwards, C308 or C310 I think.

Ill take a look, but this was mostly working before and I didnt change any caps, just solder joints, so I'm pretty sure all the caps are installed properly.
 
Well, if you don't have new caps, one of the bad ones could cause this.

And you test resistors in ohms, and test transistors with the diode test...
 
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