Nanao MS-2933 no red

[snake_eyes_ex]

I need some help. When I got my Blast City it didn't turn on. I've posted about my Blast so far here: LINK

Everything else works, except, I have not been able to get red on my tube.

What I've tried so far:

• Recapped chassis
• Messed with pots and control board
• Tried a JAMMA PCB and JVS through VGA, as well as Dreamcast through VGA
• Swapped the IC chips on the neck board each for one-another
• Reflowed the neck board
• Re-checked the main chassis for any cold solder

I'm worried it's the tube, but when I degauss I do see red for a split second. I don't know if that counts for anything, but I'm hoping there is something I've missed on the chassis or neck board.

 

[hatmoose]

You’ve done all of the things.

At this point I would be worried about the red gun in the tube.
If you have access to a CRT tester/rejuvenator this tube is very well known and it would be relatively to test it. Even if the red gun is showing dead it may be possible to recover the tube, sometimes “dead” is actually shorted and if you can burn that off…

But yeah, a tube rejuvenator/tester is the next step IMO

 

[snake_eyes_ex]

You’ve done all of the things.

At this point I would be worried about the red gun in the tube.
If you have access to a CRT tester/rejuvenator this tube is very well known and it would be relatively to test it. Even if the red gun is showing dead it may be possible to recover the tube, sometimes “dead” is actually shorted and if you can burn that off…

But yeah, a tube rejuvenator/tester is the next step IMO

Thanks for the info. I'll track down a tester.

 

[GeekMan1222]

Not sounding to well :/

But it could still be something with the chassis too but you already checked alot of the go to things.
You cannot rule out that there may be some kind of out of spec or failed passive or something in the chassis somewhere thats failing to pass the red color signal to the color drive amplifiers on the neck.

It should also be noted but this is even more uncommon but if the pin for the red gun is bad or has a bad connection in anyway this will also cause an issue.
For example there is heavy surface corrosion on the pin at the neck of the tube or in extremely rare cases the solder connection inside that pin is bad it could cause issues. (yes I said inside the pin because technically those pins you see on the neck have a very fine wire soldered to the actual pin you see.)

Personally at this point.. I would borrow, rent, buy a tube tester first and rule out any issues between the tubes guns / socket and the chassis or cabinet wiring.
(though using the VGA connection on the 2933 basically rules out cabinet cabling).

If you have a spare known working chassis that can work on that tube this can also drill down the issue a bit more.

Best of luck

 

[ShootTheCore]

With an all-white screen displayed, use a multimeter to check the voltage going into the Red gun on the neckboard by probing its transistor. That way, you can verify that the chassis is powering the gun correctly. Sometimes a color transistor on the neckboard fails and then that gun doesn’t get powered.

All three color gun transistors should read similar voltages on the neckboard if your gains and cutoffs are set identically.

If all three color gun transistors read similar voltages but you still don’t have any Red displayed then it’s 100% time for a tube rejuvenator.

 

[snake_eyes_ex]

With an all-white screen displayed, use a multimeter to check the voltage going into the Red gun on the neckboard by probing its transistor. That way, you can verify that the chassis is powering the gun correctly. Sometimes a color transistor on the neckboard fails and then that gun doesn’t get powered.

All three color gun transistors should read similar voltages on the neckboard if your gains and cutoffs are set identically.

If all three color gun transistors read similar voltages but you still don’t have any Red displayed then it’s 100% time for a tube rejuvenator.

Thanks. I'm definitely going to try this.

Can I ask where I place my multimeter's test leads? I assume it's pins 4-12, but where do put my positive and negative leads so I don't short anything?

 

[ShootTheCore]

OK, I haven't worked on this chassis firsthand, but from what I can see on the schematics, it looks like:

Red = Q301 -> Q302 -> Q304 -> Q303 -> Neck Pin 8
Greed = Q311 -> Q312 -> Q314 -> Q313 -> Neck Pin 6
Blue = Q321 -> Q322 -> Q324 -> Q323 -> Neck Pin 11

Your negative probe should always be touching ground - the metal frame around the tube is fine.
Set your meter to measure DC voltage.
Set the monitor to display an all-white screen. That way, all three color guns should be sent the same voltage.

Touch your positive probe to each of the appropriate Neck Pins first. The voltage should be roughly the same across all three.

If they are, stop here and move on to CRT Tube rejuvination or replacement.

If the Red neck board pin isn't receiving voltage equivalent to the Green and Blue, start stepping back through the transistor chain with your positive probe. Whichever transistor doesn't pass current along is your culprit. You can try swapping your suspect transistor with the equivalent on one of the other colors to see if that causes the faulty color issue to move with the suspect.

If Q301 at the base of the Red transistor chain isn't receiving current then the chassis board isn't generating it for the neckboard.

 

[snake_eyes_ex]

OK, I haven't worked on this chassis firsthand, but from what I can see on the schematics, it looks like:

Red = Q301 -> Q302 -> Q304 -> Q303 -> Neck Pin 8
Greed = Q311 -> Q312 -> Q314 -> Q313 -> Neck Pin 6
Blue = Q321 -> Q322 -> Q324 -> Q323 -> Neck Pin 11

Your negative probe should always be touching ground - the metal frame around the tube is fine.
Set your meter to measure DC voltage.
Set the monitor to display an all-white screen. That way, all three color guns should be sent the same voltage.

Touch your positive probe to each of the appropriate Neck Pins first. The voltage should be roughly the same across all three.

If they are, stop here and move on to CRT Tube rejuvination or replacement.

If the Red neck board pin isn't receiving voltage equivalent to the Green and Blue, start stepping back through the transistor chain with your positive probe. Whichever transistor doesn't pass current along is your culprit. You can try swapping your suspect transistor with the equivalent on one of the other colors to see if that causes the faulty color issue to move with the suspect.

If Q301 at the base of the Red transistor chain isn't receiving current then the chassis board isn't generating it for the neckboard.

Wow. Thank you. I’ll try this out.

 

[brad808]

No need to overcomplicate yet.

With the Mon powered just temporarily ground the red cathode on the neck board with a wire. Does the full screen light up with Red? If so you know your problem is on the chassis. If not, your problem is with the tube (... Or with the socket).

Go from there.

 

[GeekMan1222]

No need to overcomplicate yet.

With the Mon powered just temporarily ground the red cathode on the neck board with a wire. Does the full screen light up with Red? If so you know your problem is on the chassis. If not, your problem is with the tube (... Or with the socket).

Go from there.

Ah!!! I was trying to remember how to do that, I didnt want to say anything though.
But yeah if you ground the cathode pin in question for just a moment, then it runs the color gun at full power and you can quickly rule out the gun or socket that way.

I never had to do it though since I just own a tester.. I kept forgetting if it was a simple grounding or something else.

 

[snake_eyes_ex]

Whelp, did the voltage test and it appears each color pin is reading a similar voltage on the multimeter.

I might try this grounded wire trick next, but it's looking like a tube rejuvenation is in my future.