Nanao MS9 29 turning red

[brad808]

So the last week or two the monitor in my driving cabinet has been turning red/ pink. This isn't a constant pink but comes and goes. It seems to be very consistantly around 15 mins or so after I turn on my monitor. I'm not sure if there is a bad solder joint on the chasis or if a bad cap or what. Is this a common problem with a known solution? Any ideas where some good places to start looking for the problem are?

The monitor is hooked up to a powercolor HD3450 using soft15khz and powerstrip from windows xp. I will try and hook up the monitor to my mame cabinet to confirm that the problem is indeed with the monitor and not the video card or vga cable hack.

Any help is a appreciated.

[lilshawn]

sounds like a drive transistor is going bad on you. soon enough the screen will always be red. as they heat up and get hot, the transistors will short, causing the whole screen to go red/green/blue.

just a matter of finding the right transistor on the neck card and swapping it out.

[MonMotha]

You can test lilshawn's diagnosis by swapping the red drive transistor with one of the other two.  If the problem moves to another color primary (green or blue), you've confirmed the problem.  If it stays with red, it's some other problem.

[brad808]

Thanks for the info guys seems like it should be fairly straight forward to see if that is in fact the problem.

I'm yet to pull the monitor out of the cabinet but I just went and took a peak at it. Are the rectangular white components going to be the drive transistors? Possibly the component in the black heatsinks?

[lilshawn]

the rectagular blocks are resistors... not what you are looking for.

the heatsinks are what you are looking at. its gonna have a three legged component attached to it. these are transistors. if you decide to replace them, there will be some numbers etched onto them. just find ones with the same number on them.

[brad808]

OK so I've located the transistors. They were in the black heat sinks. Now there doesn't seem to be any clear indication as to what transistor is for what drive? The transistors are located at 302, 312, and 322. They don't appear to have an R, G, B or anything like that around them.









This is the markings on the transistor



So if I find a C4001 I should be able to direct swap it in? Is there anything else I should be looking for as far as specs go?
Would this be a suitable replacement? http://www.ebay.ca/itm/2pcs-NEC-2SC4001-C4001-NPN-Silicon-Power-TRANSISTORS-/390314200915?pt=LH_DefaultDomain_0&hash=item5ae08a0f53#ht_1107wt_1344 Edit: GRRRRR just noticed that seller doesn't ship to Canada 

[lilshawn]

the number is what matters.

2SC4001 is what you need.

as for which one... even the scematics are terrible for not telling you. but you can trace from the tube socket pin for the red gun cathode back to the transistor. sometimes there will be stuff screened on the board for h k g1 r g b gnd etc. around the pins on the socket. it looks like pin 5 on the scematic but i cant be 100% ive highlighted the color circuits, but i cat read part locations.

[brad808]

Thanks for all the info. Those schematics do look terribly hard to follow though. I think what might be the best plan of attack is to take all 3 transistors and rotate them all clockwise one place and see if in fact the problem does show on another colour. If this is the case and it is a fualty transistors then I will probably just look for a Canadian supplier, or at least one that will ship to Canada, and order 3 new ones. Seems like they should only be a few dollars and will probably save quite a bit of time trying to decide which belongs to which.

[brad808]

So I haven't gotten a chance to change the transistors around yet but I've been looking for replacement parts in the event that I do need to change them. The problem is that I can't find them anywhere that ships to Canada except for one or two places that will cost $30+ dollars. I spoke to digikey which is good in Canada but they don't carry that part number. The guy suggested MJE3439GOS-ND as an alternative.

http://search.digikey.com/scripts/DkSearch/dksus.dll?x=19&y=17&lang=en&site=ca&KeyWords=MJE3439GOS-ND

Any insight on this? Will these transistors in fact be compatible?

[lilshawn]

i would say no.
the difference is the current switching speed.

the MJE3439G has an fT of 15mhz

the 4001 has a fT of 200-300mhz

in a slow switching application I it would be fine. (being used to turn on or of lights or motor speed controls where the switching speed isn't as important)

but in monitor applications the transistor turns off and on potentially every other pixel. Ive tried to sub lower switching speed transistors and it results in an extremely blurry image, as the transistor cant switch the guns fast enough.

your best bet is to ebay up yourself some from hong kong for 2 bucks each and wait the few weeks it takes to get them.

/b/ro tip: order extras for just in case *thumbs up*

[brad808]

So yesterday I got my transistors in and changed them around with the new ones c4001's. The problem is still there. So the problem is either somewhere else on the monitor or possibly the video card/ vga cable hack. I'll try and eliminate the vid card and cable because that should be easy enough to do because I have another arcade cab right beside it to swap with.

Any other ideas?


Edit: Tried other computer with new video card and cable hack and problem still happens so I believe it's in the monitor itself

[lilshawn]

keep working up stream. there is some transistors, diodes and then an IC (i assume a video amp of sorts) this is your next logical step. these items will be on the main board. Check the ribbon cable (or wire bundle) connecting the main chassis to the neckboard for shorts.

also there may be an issue with the supporting hardware (pots etc.) for adjusting the Red Green and Blue check them for cracks and broken solder too as well.