Disabling PSU / Checking Isolation Transformer

[DonDrimeXm8]

After several months I've finally got all my stuff together and I'm trying to hook up a working MAME cabinet to play, but I'm pretty much lost with all the wires and connections in my cabinet. It's a SEGA Aero City cabinet with a Nanao monitor and I'm stuck with a few easy (?) problems in trying to unhook the PSU because there won't be any PCB running and also the embarrassing problem of veryifying that there is an isolation transformer and that I don't accidentally unhook it.

[DonDrimeXm8]

A few more (if any different kind are needed I can put them up too)...

[MonitorGuru]

There is no isolation transformer showing in any of the pictures you posted.

Either it is mounted elsewhere in the cabinet (possibly, though unlikely/stupidly on the back of the metal box for the coin door bucket on the right of your pictures) or on the monitor shelf or on the monitor frame itself.

Or, it is possible the monitor doesn't require an isolation transformer.  But DO NOT ASSUME THAT. Check around elsewhere to see if you can see a transformer sitting anywhere, and post shots of around the monitor/monitor model number.

(First..dude... you REALLY need to clean that cabinet.. and remove all the loose change.  That COULD cause a short if it fell on one of the connectors just right!)

To help you identify things, here goes:
Inside3.jpg: This is the external facing power switch and line interference filter box. Follow the wires from this and it should lead two places. First to the external power cord, second, to the switch-mode DC power supply.

Inside2.jpg: This large rectangular thin box is the switch-mode DC power supply. This is basically identical to what you have in your personal computer, just without a fan.  This provides DC power to the circuit board only.

Inside1/4.jpg: This shows another master power switch that should be in line with the other one at the back of the cabinet.


Here is a nice diagram to understand where these wires go and what they do:

[DonDrimeXm8]

Thank you MonitorGuru!

The transformer definitely isn't behind the coin door; just the coin mech.  Looking around I still can't find the isolation transformer and presumably also the step down converter (since it's a Japanese monitor supposed to run at 100v).  It's possible it doesn't need one; I played the system right before bringing it home and it apparently had been run in public for some time too, but I'm not confident with my ability to even discern that an isolation transformer is present.  The monitor is SEGA part no. 200-5187-15 and model MS8-26SG, if it helps.

Regarding the switch-mode DC power supply -- is that where I unhook everything connected since I won't be running a PCB? 

The cab is cleaner and without change now too; should have cleaned it a long time ago.

Here's two more pictures of the monitor area, taken awhile ago (I can borrow a camera and take more pics if they're needed).

Thanks again MonitorGuru!

[MonitorGuru]

The monitor is a Nanao brand model MS8-26SG. I do not know anything about them, but perhaps Ken Layton does.

I saw a pic of the monitor circuit board on another site and it appeared that is *possibly* has on-board isolation, but I am not sure, so don't assume it does.

Here is how you can find out if it is isoltated.

[DonDrimeXm8]

Thanks once again MonitorGuru; your patience is really appreciated.

The black wire is the power cord, which travels to the grey connector hanging in the back right of the cab.  The red ones with the black electrical tape come from about one centimeter to the left of the white knob on inside6.jpg and connect to the yellow connector beside where the power cord connects.  The white knob has numbers 1, 2, 3, and 4 on it, if it matters. I circled where these wires connect on the attached picture; the grey connector is the power cord and the yellow is the red wires with electrical tape (no idea what the pair does).

From the yellow and grey connectors it seems the wires travel together, along with two wires from the noise filter, to the circled connectors near the front of the cab, which form a jungle of wires and connections.  The pinkish wire in front of the 2 cirucular buttons on the strip is actually just from a button that was connected, but isn't anymore.

[MonitorGuru]

Well, I officially have no definitive idea what they're doing with the two red wires with the electrical tape on them. The larger flat black definitely should be the incoming power.

The *ONLY* thing I can possibly think the red wires are used for is a switch extention.

[DonDrimeXm8]

MonitorGuru, thank you so much for all the help! My cab is running smooth and that button was the manual degauss, just as you thought.  My cab would still be sitting there unplayable without your help.