Main > Monitor/Video Forum
NeoGeo mvs-4-25 (WG K7000 compatible chassis?) w/ color separation, size issue
Sememmon:
I've gone all over the the components.. nothing seems loose. I'm figuring either I there's a bad solder joint.. or I broke a trace I'm not seeing.. or I damage a component.
I just don't know how to tell which it is. =( I've got a replacement IC coming for the LA7831. Maybe that'll help. =|
lilshawn:
check R91 (3.9 ohms)
D13 on diode check mode should read somewhere abouts 0.4 to 0.5something probably have to lift one end out of circuit to get a good reading.
C48 double check polarity. if it's backwards it could be dragging down the voltage causing it to act dead.
if you are changing out IC3, you may as well order and change IC2 as well. they are pretty tightly integrated to each other and a detrimental failure on IC3 can cause failure in the other by back feeding into the IC by voltage going "in" through the output.
Sememmon:
Thanks for the suggestions. I will see about swapping IC2. I had an arcade tech visit today, but we were unable to make any headway. It was good to have someone with more knowledge check my work, but he admitted to not being a monitor expert.
Regarding the voltages you suggested checking, I'm not sure how I can go about doing that with the monitor in the cabinet. It'd be pretty awkward. =| Would be a lot easier if I had an external power supply so I could power it up on my desk. I suppose I could solder in a bunch of test wires like with IC3... hm.
Sememmon:
Finally got this resolved. Chad at arcadecup.com did a great job fixing me up. He replaced multiple ICs as well as fixed a trace and solder pad point. Everything is good to go now and looks better than it did when we started.
I also spent a little time trying to fix the top-left corner convergence. I've made some headway there, but it seems to be very much a black art with a lot of trial and error. Hopefully I'll figure it out eventually, but am pretty happy with how well it is performing now.
lilshawn, thank you so much for the assistance throughout this issue. I really appreciate it! :cheers:
lilshawn:
cool cool. if you want a little insight into setting up convergence, the Wells gardner K7500 service manual has a really good write up (starting on page 5)... it's basically universal since most tubes are designed in similar fashions.
https://www.wellsgardner.com/wp-content/uploads/2016/08/K7500.pdf