Nanao monitor help in Sega Turbo

Brooklyn

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Hi guys, I have a Sega Turbo mini with the 13" or 14" Nanao monitor. The problem is the picture has rolling waves for about 20-30 seconds, then the monitor goes in to shutdown.

I replaced all of the caps including the big filter caps. Also inductor L902 was broken/corroded off the board when I got it. I replaced it with an equivalent from Mouser.

Before I go and re flow every solder joint wanted to check in for any advice.

There is a video of the issue below:

https://youtu.be/isUlBVrjux4
 
That looks like an AC ripple, possibly. If you have another ps, I'd try that first. Can't remember if Turbo runs on a switcher ps or not. Could always test the monitor with another game cabinet, to isolate whether it's a monitor, or game cabinet issue.

Caps could also play part, never hurts to redo those and resolder your critical points(header pins for connectors, ect....), to keep the monitor healthy.
 
I had this issue with the larger version of this monitor and couldn't figure it out. My B+ voltage started low then gradually increase (with the shutdown circuit disabled). The screen also showed the same effect you're seeing on yours. Then it would shutdown... I bought s new chassis that arrived with a broken flyback, swapped it with mine. Then everything worked perfect. I know it doesn't help you to just buy another chassis! But that's how I got mine to work. I will be following this.
 
Hi guys, no luck so far. Chassis is labeled 120V but it won't run off mains power or from my Galaga. The input voltage to the monitor I measured in the Turbo cab is 100V.

I bought a similar chassis for parts, however this chassis is labeled 100V. I tried it just for kicks and it blows a fuse when powered on, even though the cabinet appears to output 100V

Using the parts chassis I replaced 4 matching transistors(Q901, Q401, Q402, Q503) from board to board but no luck, still wavy and goes into shutdown. There is one smaller transistor left (Q502)that I haven't changed due to the numbers not matching between boards.
 
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Well, I still haven't figured this one out. I replaced all the mentioned transistors with new versions and still no improvement.

Any other ideas?
 
Check the PSU section transistors, pulling them from another chassis that's unknown is no good. PSU failures on these are fairly common so you could well have just put another bad transistor in it.

You can pull F2, measure the B+ there to chassis ground and I bet its high.
 
Just noticed this!

Using the parts chassis I replaced 4 matching transistors(Q901, Q401, Q402, Q503) from board to board but no luck, still wavy and goes into shutdown. There is one smaller transistor left (Q502)that I haven't changed due to the numbers not matching between boards.

You only replaced one PSU section transistor there?!!

check Q901, Q902, Q903, Q904
 
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