Too much blue on the monitor

[Halo]

I'm trying to help someone with a blue problem at long distance - always tricky!

The monitor is a 29" Nanao.  What should be black on the screen is actually dark blue and the screen is also tinted with blue.

Now, here's what I would do, but I may be missing a whole range of basics here! Please tell me if so.

1) Try blue pot and blue gain pot
2) Measure what coming out of the PSU with a meter at the edge connector.
3) Switch red and blue video wires to see if I then had a 'red' screen.  My logic (may be wrong) would be that a red screen would indicate too much voltage or a problem before the chassis, whereas if it remained blue, then the problem is actually on the chassis somewhere and then I'm stuck!

Number 2 may already indicate what I'm looking for in number 3 of course.

I have very little knowledge monitor wise, so please do jump in and pull the above apart for me! It will be extremely helpful.

Multiple boards have been tested - interestingly the MVS won't work at all, the other boards are totally normal but blue.

Any suggestions would be appreciated!

Thx

[Halo]

Apologies - it's a 29" Toshiba, not Nanao.

[Ken Layton]

What is the specific make and model of the monitor? Is it a Nanao or Toshiba?

Is your cabinet wired to Jamma standard? If so Neo Geo 2 slot, 4 slot, and 6 slot are NOT Jamma. Only the single slot boards are Jamma.

[Halo]

Hi Ken!

Its a Toshiba, I will get the exact model number.

The cabinet (Sega New Astro City), was wired for System 2 we think running Virtua Fighter. We changed over the internal chassis connection from 'Hi' (24K) to 'Lo' (15K) and then replaced the video input plug (there were two, one for each system).

The MVS is a 4 slot, and we tested this on my own cabinet and it works fine here on a JAMMA connection.

We're not altogether sure if any other wiring modifications need to be made, but judging by the cabinets schematics - it's a JAMMA loom whichever system is used - the VF2 connector simply plugs into the JAMMA loom and is thus converted for that system. I can post up a schematic of this if that would help?

Many Thanks

[Ken Layton]

Here are two links that describe the differences between Jamma and Neo Geo's MVS wiring standard:

www.hardmvs.com/html/jamma.htm

www.hardmvs.com/manuals/Jamma2NeoGeo4SlotPinout.pdf

I have seen instances of people blowing the amplifier circuitry on their Neo Geo MVS boards when plugging into Jamma harnesses because the speaker connections (as well as test switch) are on different pins.

[Halo]

Thanks again Ken

[menace]

I'm having the same problem with the pentranic 1425--the picture is there but its all blue--the individual color pots do bring in color but the overriding color is blue--any thoughts?

edit: after some research, it seems this problem is linked to tube failure in a high number of cases.  Also cold soldered joints on the neckboard around the color transistors was a factor as well.

[Halo]

Hey thanks for the edit - will be useful to remember!

In this case, also Ken you were right - the MVS sound has definitely gone, almost certainly through plugging it in to the JAMMA loom. It was a timely reminder, the day after I sold a JAMMA cab on ebay, and the excited buyer told me he was going to throw in his 4 slot!

I forwarded on the info here, and hopefully we've saved someone the same fate!