29" Nanao ms2931 Tri-Sync Monitor Issue

[sayitaintjonas]

Hello, I have a Sega Blast City cabinet with a 29" Nanao ms2931 Tri-Sync Monitor. The monitor seems to work fine, but it will sporadically do something strange. I'm not sure how best to describe it, but it will click and then the screen appears to shrink and fade and then go back to normal very quickly. It almost seems like the power cord has been pulled from it and then reconnected very quickly. Sometimes it will do this 2 or 3 times within a minute and sometimes it will go 20 minutes without doing it.

Does this make sense to anyone?

[MonMotha]

Sounds like perhaps a shutdown triggered by the x-ray protection or similar kicking in.  Try turning down contrast.  If this monitor has multiple input options (such as a PC input and a conventional "arcade" input), make sure you're using the appropriate one.  Using the wrong one can result in oddball settings issues due to the unusual input impedance that can trigger ACL based shutdowns on some monitors.

Could also be a poor solder joint or similar near the power supply.

[qrz]

typical shutdown circuits do just that . once triggered , the set dies .
pwr must be removed for short period of time to allow voltages to bleed off.
then , the unit may be repwr'd .  shutdown will reoccur until fault corrected

suggest inspecting the pcb for poor solder connections . u will likely find some 

a slow pic fade to dark/black with a more rapid fade to normal is typical of intermitent loss of filament voltage on the crt.
it IS a tube , and most active tubes use a heated cathode ( that orange glow ) to stimulate electron emission.

and no, glowing RED plates is NOT good 

qrz

[MonMotha]

If it's not a protection based shutdown, it makes me wonder what the "click" is.  Is it relays clicking?  If so, usually only a couple relays on the board: degauss and one or two on S-correction caps.  Either of those clicking indicates something like a confused/reset MCU (I presume this is a digital monitor?) to me.  If it's just a soft "click" from sudden changes in power levels, that points more towards just a bad solder joint.

My KT-2914F (Betson) seems to restart after it does what the OP describes.  Only does it when I have contrast *cranked* since I'm hooking up MK2 to the PC input and it forms a pretty bad divider with the 75ohm inputs (high-Z outputs on that board, I guess), so I suspect it may be hitting the ACL shutdown periodically or something.  Maybe it has to do with the weird scanrates MK2 uses; I dunno since I can't reliably reproduce it.  I'd love to know what causes it, too