WGM2574 - Missing blue.

streetfighterken

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I picked up a clean 1998 Midway cab. Cleanest untouched chassis I've ever seen. All looks well on-screen besides the absent blue. Where do I start? Must be something on the neck board? Thanks. ImageUploadedByTapatalk1436836402.447689.jpg
 
Check all of the solder and traces for the three color transistors on the neck board (ones with the heat sinks).

This neck board is known for having a lot of problems in that area.

If that doesn't get it try swapping the blue transistor (Q503) with either the green (Q504) or red (Q505) and see if the problem moves.

If you need it repaired I repair this chassis. Cost to repair $40.00 plus parts and return shipping.
 
http://www.organizedmassconfusion.org/2013/09/04/wells-gardner-p719-neckboard/

I consider this a mandatory repair for any of these era WG monitors. I had one last week where it looked like the trace was fine and sure enough it had just enough of a break to not work. it's normal for the solder pads to lift, this is basically caused by the heatsinks not dissipating heat well enough, and the heat just gets trapped at the board. the hook method I use is to get the transistors to grab the board so they won't flex -- this is helpful if your traces/pads are good, but are lifted.

I encourage after you're done doing whatever you choose to do that you run continuity checks backwards from each of the 3 legs on the 3 transistors to make sure you have connection.
 
Great info. I'll hit the transistors first and rig a fan to blow on that part of the neck board. Interesting that these models carry so much more heat than past WG models.
 
their neck boards were just a terrible design all around.

clean up and jumper all the traces on the transistors to prevent it from happening again.

Peace
Buffett
 
Well that was easy -- tested and confirmed bad transistor.

Where can I find SANYO 2SC3782 transistors?

I found the specs but I'm unable to find an alternative with those specs. I found a seller on eBay but he sells used ones.

Also most of the pads/traces lifted when I removed the transistors from the board. Lifted traces are "ok" as long as the connection is still being made right? I mean at that point they're just acting like a wire. I'll probably jumper all of it anyway but just curious.
 
i have used ones here ATM.

i rarely have to replace them so i have been pulling them from broken neck boards.

Peace
Buffett
 
Thanks to everyone's input, I'm up and running again. Special thanks to Buffett for the spare transistors.

And here's my cooling solution:

 
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