[Solved]Nanao MS2930 - Blue screen shuts down

[JSN_]

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?

 

[GeekMan1222]

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.

 

[advans14]

Safe to say any of these import games have out of spec caps at this point.

 

[GeekMan1222]

Safe to say any of these import games have out of spec caps at this point.

indeed
We will be doing a Full recap on this chassis once its fixed as well.

 

[GeekMan1222]

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.

 

[advans14]

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.

nice work, in my experience transistors are a high failure point on most game shit.

 

[GeekMan1222]

Age and heat does a number to transistors sometimes. The Neck board isnt exactly the coolest of locations

 

[JSN_]

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.

¡Bravo! Well done @GeekMan1222

 

[GeekMan1222]

Here is my completely amature video of me working through the problem some and fixing it.

 

[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.

 

[Kidkaos]

Awesome work Geekman!!

 

[vaughan14]

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.

Thanks for this, I managed to fix mine by replacing the same component.

 

[Kidkaos]

@Revrun91