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[Solved]Nanao MS2930 - Blue screen shuts down

So quick question may or may not be related. I recapped my power supply, because it was pretty ratty. Seems to be working now, but I just powered up with the screen completely disconnected, and I noticed the fan wasn't spinning.

Could this all be related to a power issue? Just checking before I delve more into the monitor.

EDIT - I forgot to plug the fan into the 2 pin connector. Doubt this is an issue, but how funny would it be if it was?
 
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As a note I now have this chassis under my possession. Still working through it not really feeling like posting the entire work log.
But in short the issue follows the chassis so you can completely rule out the CRT tube losing its guns (highly unlikely that 2 guns just fail for no reason at the same time.)

I ran a few tests the contrast/drive is kinda out of control and this isnt really screen related either. The B+ was low around 174~ VDC stable so I brought that up to 180VDC stable.
The HV off the anode also seemed to test slightly low but I really refuse to touch anything involving the HV setting if its running fine especially with these chassis's the output/picture to the tube was very stable. This is a video/color issue.

Ill have some updates if I can narrow things down further

The interesting thing is if I increase the video level being fed into the video amplifier then I can actually get colors to be driven on the tube I am testing with. Although doing that will very much blow everything out involving the picture because you increased the video level but I do get all 3 colors. I have a suspicion that the video amp may have an issue or something between the video amp and drive transistors is bad.

In short, tested passives, reflowed the video block and the neck board ran some basic checks on the color drive transistors, and ran some video input tests.

Several caps in the video amps block tested poorly with ESR and I replaced those now. Will test again tomorrow.

Edit: I realize the way I wrote this might not really convey the series of event chronologically, The chassis did not have any parts replaced or reflows until after the initial video input tests and mucking around with some pots was done.
 
The chassis is now repaired. Ill have a very amateur Youtube video posted about the fix/process and ill link it here when I actually edit it tonight.

But basically what was happening is the Blue drive was being driven at max because of another transistor Q323 being shorted.
This shorted transistor was pulling down the voltage for the output/drive transistor for the blue gun which will increase the bias/output/drive of said color.
The reason you couldnt see the other colors was a combination of the screen voltage being too low in combination to the sheer amount of blue being driven compared to the other colors.

Color and picture output is very nice and stable theres no shut downs happening and the entire neckboard and video amp block was reflowed. B+ was corrected but will have to check that one more time once we recap the entire chassis.

:thumbup:
 
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GeekMan1222 said:
The chassis is now repaired. Ill have a very amateur Youtube video posted about the fix/process and ill link it here when I actually edit it tonight.

But basically what was happening is the Blue drive was being driven at max because of another transistor Q323 being shorted.
This shorted transistor was pulling down the voltage for the output/drive transistor for the blue gun which will increase the bias/output/drive of said color.
The reason you couldnt see the other colors was a combination of the screen voltage being too low in combination to the sheer amount of blue being driven compared to the other colors.

Color and picture output is very nice and stable theres no shut downs happening and the entire neckboard and video amp block was reflowed. B+ was corrected but will have to check that one more time once we recap the entire chassis.

:thumbup:
Click to expand...
nice work, in my experience transistors are a high failure point on most game shit.
 
GeekMan1222 said:
The chassis is now repaired. Ill have a very amateur Youtube video posted about the fix/process and ill link it here when I actually edit it tonight.

But basically what was happening is the Blue drive was being driven at max because of another transistor Q323 being shorted.
This shorted transistor was pulling down the voltage for the output/drive transistor for the blue gun which will increase the bias/output/drive of said color.
The reason you couldnt see the other colors was a combination of the screen voltage being too low in combination to the sheer amount of blue being driven compared to the other colors.

Color and picture output is very nice and stable theres no shut downs happening and the entire neckboard and video amp block was reflowed. B+ was corrected but will have to check that one more time once we recap the entire chassis.

:thumbup:
Click to expand...
¡Bravo! Well done @GeekMan1222
 
Reflecting.
The fact that having no input with the monitor on resulted in a solid blue image should have immediately alerted me to the fact that the blues drive may be stuck high for some reason. But like I said I only worked with color issues like this a handful of times.
 
GeekMan1222 said:
The chassis is now repaired. Ill have a very amateur Youtube video posted about the fix/process and ill link it here when I actually edit it tonight.

But basically what was happening is the Blue drive was being driven at max because of another transistor Q323 being shorted.
This shorted transistor was pulling down the voltage for the output/drive transistor for the blue gun which will increase the bias/output/drive of said color.
The reason you couldnt see the other colors was a combination of the screen voltage being too low in combination to the sheer amount of blue being driven compared to the other colors.

Color and picture output is very nice and stable theres no shut downs happening and the entire neckboard and video amp block was reflowed. B+ was corrected but will have to check that one more time once we recap the entire chassis.

:thumbup:
Click to expand...

Thanks for this, I managed to fix mine by replacing the same component.
 
I’ve currently got the same issue going on with my new (to me) Blast City with a Nanao MS-2931. I tried the usual things, jiggling all of the wires and connectors between the JAMMA harness and the monitor, and tried jiggling the neck board, to no avail.

The monitor was running great when I demoed the cab before taking it home. We had removed the monitor before transporting the cab, and then I put it back in Tate. First time firing up the cab after getting it home and this happened.

UPDATE: So I watched @GeekMan1222's video and it looks like I'm having the same exact issue with the same transistor, Q323 on the neck board. I performed the same checks that GeekMan performed with a multi-meter and it looks like my Q323 is shorted out. Kind of wild that I'm having what appears to be the same exact issue.

The MS-2931 service manual indicates that this is a "2SC4218 AA", which appears to be a part made by Sanyo. It appears to be long discontinued so I am trying to search for old stock or a suitable replacement. If anyone has a 2930/31 neck board for parts that I could salvage one of these transistors from I'd greatly appreciate it.

Here's a short video I recorded earlier showing my issue:
View: https://www.youtube.com/shorts/0di1vPHL1bM
 
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bitkid said:
I’ve currently got the same issue going on with my new (to me) Blast City with a Nanao MS-2931. I tried the usual things, jiggling all of the wires and connectors between the JAMMA harness and the monitor, and tried jiggling the neck board, to no avail.

The monitor was running great when I demoed the cab before taking it home. We had removed the monitor before transporting the cab, and then I put it back in Tate. First time firing up the cab after getting it home and this happened.

UPDATE: So I watched @GeekMan1222's video and it looks like I'm having the same exact issue with the same transistor, Q323 on the neck board. I performed the same checks that GeekMan performed with a multi-meter and it looks like my Q323 is shorted out. Kind of wild that I'm having what appears to be the same exact issue.

The MS-2931 service manual indicates that this is a "2SC4218 AA", which appears to be a part made by Sanyo. It appears to be long discontinued so I am trying to search for old stock or a suitable replacement. If anyone has a 2930/31 neck board for parts that I could salvage one of these transistors from I'd greatly appreciate it.

Here's a short video I recorded earlier showing my issue:
View: https://www.youtube.com/shorts/0di1vPHL1bM
Click to expand...
Not totally wild that the same parts are dieing with age some things are driven harder or dont have good long term life expectancy.

The best solution is to find some kind of equivelant transistor or buying or using a parts PCB to replace the part.
 
GeekMan1222 said:
Not totally wild that the same parts are dieing with age some things are driven harder or dont have good long term life expectancy.

The best solution is to find some kind of equivelant transistor or buying or using a parts PCB to replace the part.
Click to expand...
I’ve found exactly 3 new old stock transistors but I haven’t gotten to replacing the Q323 yet to test my hypothesis. I’ll update this thread once I’ve gotten around to the fix.
 
I fixed my MS-2931 blue screen problem by replacing the shorted NPN transistor at Q323 with a NOS part, Sanyo C4218. When I fired it up, I had a completely black screen and thought I'd borked it but then I remembered that I had previously turned the flyback all the way down. Whew!

Each color channel on the MS-2931 (and I presume the 2930 as well) neck board has a pair of NPN and PNP transistors near a big transistor with a heatsink on it (didn't look up what part the big guy is). The NPNs are Sanyo C4218 and the PNPs are Sanyo A1624. I only ended up replacing the one C4218 at Q323, though. Just thought I'd post this here for the next poor soul who encounters this point of failure or wants to refurb their neck board.

My father in-law suggested placing a cooling fan in the cab so that it could blow across the neck board, to avoid excess heat build-up in this area. I may end up doing something like that.

As I mentioned previously, this is exactly the same fix that @GeekMan1222 performed on a MS-2930 neck board in their YouTube video linked a few posts up.
 
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Glad to see this fix helped you. It must be a higher failure prone issue. These transistors iirc work together so if one of the two or so related to that color channel goes out then the color is out.
 
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