ok, so today I started dismantling my old mame cabinet in the garage and I decided to take a quick brake and play on my Sega Scud Race for a bit. It all started up fine and after a few seconds I began playing as usual. About 2 minutes in to a race the screen went white with grey lines sitting still across the screen horizontally. there was no warning, flickering, picture rolling or bad sounds. It just went white. The game plays on, with sound and everything. :banghead: Restarted the machine and same thing each time. When I disconnect the RGB cable from the motherboard the lines move around then screen but return to still when reconnected. So new monitor chassis board? or find someone who can fix this? I have had a look for a model number for the board, but no luck so far. all I know is its a mid rez 29" screen. I have no luck with arcade machines at all :crying:
Been looking around inside the monitor for any model number. When looked under the monitor board I could see lots of discoloured solders around the high voltage areas and a few cracked and grey ones in other places. I wouldn't be surprised if that caused the problem. I'm going to leave it for a day or so, then discharge and remove the board and try to tidy up the soldering
Thermal expansion could cause what you saw on the high voltage connections. I've never worked with soldering on high voltage lines or even CRTs but it could explain why it worked for a few minutes then stopped (warms up, expands, creates open circuit) but this seems apparent already.
doing anything like this with arcade monitors scares the hell out of me. I've removed and discharged CRT's before but its still worrying.
If you get a wire with a crocodile clip on each end, you can connect it between the CRT's anode and one of the mounting lugs. No chance of any charge building up while you're working. I'd also discharge any big capacitors with a resistor. I've been 'surprised' by a cap before, and won't make that mistake again. As for the flyback lines, check the soldering around the line output transformer.
perhaps things are looking better now. I contacted the guy I got the cab from and he has a contact who specialises in monitors and chassis boards. I'll be going to collect a Naomi Net City cab soon so I'll drop the board off with him. I have a home made discharging tool left over from all the problems I had with my Sega Rally cab. I used a screwdriver with thick rubber handle grip and 100meg ohm resister. But I'll be leaving the cab for a couple of days just in case
Try turning down the Screen knob (it'll be one of the two knobs on the black part behind the flyback coil), to see if you can get the picture to go from white to black. You better hope that it is not a flyback that has gone as most Sega games of the era used a Nanao chassis that can be quite difficult to source a replacement for. However I am going to guess that one of the flyback connectors has a dry joint or that one of the HOTs have failed which means with a recap it should not cost too much.
I'll remove the chassis tonight and get a photo up, I'm still thinking its solder joint related. All the solders for the flyback (like a ring of them) are brown (old flux?) or grey. I'll see better when its out
Yes it's usually good practice to completely remove the old solder with a desolder pump, and then apply 60/40 leaded solder (try and avoid the lead-free crap). Maybe resolder and clean the connector from the chassis to the CRT neck-board, as the loss of RGB drive can often give a bright raster (might also be down to a bad resistor or cap lowering the RGB volts). Re-solder areas that have signs of heat stress (around heat sinks, areas where PCB is discoloured etc). If there's no improvement try tapping areas with something plastic (a ruler for example), as you can often find a dry joint that way.
I discharged and pulled the board this evening. had a good look around the underside and all the marks I could see with the torch turned out to be old flux after all. tested round with a mulit-meter and found no broken lines. I'm not messing with it. Its going to the repair guy later in the week.
found a thread on Arcade Otaku, same chassis Nanao MS9-29T. http://forum.arcadeotaku.com/viewtopic.php?f=4&t=15790 This guy had the same problem, and the video he posted looks exactly like my screen except mine does not shut off and keeps going. Might be a bad diode, but the guy never said if it fixed it or not
Brown crusty flux left on the board usually means a bodge-job repair by an operator in the past (they tend to use acid-fluxed plumbing solder instead of electronics solder as it's cheaper, but it corrodes the board!). I've had good fortune in the past by simply cleaning it all up, removing the old solder and resoldering all the dodgy joints; they usually weren't properly resoldered on the previous repair so they eventually fail again. Worth a go if you're feeling brave, if not the nice monitor people will sort it out for you Stone
Would have taken a look if you were closer - bit of a trek! Monitor guy should be able to sort it, though ;-) Brown joints is common on HT circuits - they can get rather warm!
wow I forgot all about this thread I started on here. I hate it when these threads get left hanging. I got the Chassis fixed, was a simple diode in the end but the monitor needed totally recalibrating when I got the board back, must have been down to the tube and remote board he used. Also the picture was upside down and back to front. That was my fault not making better noted when removing the board, easy to sort that. All well and good now and I was playing it through my summer brake.
