Nanao MC-2000-S missing color

[cornerstone]

Blue. The missing color is blue, which is shown in the attachment photos.



This is the original monitor from an old Pengo cocktail cab.

So a few years ago, I sent this chassis off to the usual place to get it fixed and they returned it, supposedly with a cap kit installed, saying they didn’t detect any problems. I figured with the age of this monitor, the blue gun just went out. I was never able to find the CR25 attachment for the rejuve machine to see if I could blast any shorts out, so it just sat there.

For some reason, today I decided to google around and came across this very helpful post on KLOV:
https://forums.arcade-museum.com/th...my-in-depth-guide-to-fix-color-issues.449073/

It made me realize I never really checked my diagnosis of a busted monitor. So I switched the blue and green on the neck board and wouldn’t you know it, blue showed up in the green spot.

So using the diagrams from KLOV,
I’ve looked at the transistors in the blue color path:

and the manual calls out these types of transistors

for q105,q106, and q303.

I am not familiar with transistors but I can solder. My questions are:
1. Are my inferences correct about the monitor not being the source of the color issue?
2. Are the transistors the next path to go down?
3. If so, I may need a short how-to on properly installing them and I need to know which ones to get.
Thanks everybody!

 

[rolins]

Funny enough i just had this issue on my Amiga monitor. It was missing blue color as well. Turned out the culprit was an open transistor and a shorted diode on the blue output before the gun.
I think your assessment is right, change the transistors along the blue signal path. You could also check the transistors in circuit if they're shorted or open with your multimeter set to diode test mode. Make sure the power is off and tube is discharged when you do that though.

 

[cornerstone]

I seem to have messed up the monitor a little further trying to reflow some solder on a neck board transistor.
Not sure what I did, but it’s super bright, like the voltage is way too high and I can’t turn it down.
So I think I’ve made it worse. I’ll update this thread with some pictures, but I need to take a break to avoid frustration here. Thanks for the encouragement on the color issue though

 

[nem]

You sure you didn't bridge something?