trouble shooting my 720 machine... STILL... anyone else have one that can tell me...

720fan

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trouble shooting my 720 machine... STILL... anyone else have one that can tell me...

so here is my background on this..
i have a 720 that was working years ago, when I first got it, i had to replace the +5 switcher..after which it worked fine for a while...One thing that always worried me was that on the red wire coming off the switcher (+5 i believe) it would get very hot, so i put a fuse inline to protect the boards...
one day it stopped working, and i kind of gave up on it and recently i have pulled it out of storage and have been trying to give it life.

i put in a new +5 switcher, tested all voltages, read +5 on both video and cpu boards, which light up, i tested all the voltages coming off the transformer brick got the 2 15 lines and the 18 line ok...i have tried it with 2 different sets of video/cpu, and audio 2 boards, both believed to be working and good, the last one i sent to el dorado and they told me were working fine as well.
i've pulled out the harness cleaned all connectors, tested for continuity on all wires...
when i turn it on i hear the speakers pop, then hum consistantly with volume up all the way, the marquee and coin slots light up, the monitor is on, but no picture but if i turn up the "Screen" it gets light...the game does not boot at all, and there is NO start up sound..
when i try to "coin it" nothing happens, when i try to click player 1 or 2 nothing....
ive tried booting it with the monitor disconnected to hear sounds..nothing
ive tried to boot with no coin assembly attached to the audio 2...nothing
ive tried to boot it with no control panel attached...nothing
this has to be something so simple but im missing it? anyone have any ideas or answers to the questions below?

thanks again board members for the help with this.

will it boot up with no coindoor connected to the audio 2 board?

will it boot up with no control panel connected to the audio 2 board?

will it boot up and do you hear sounds with your monitor completely disconnected?

on the transformer, there is a red/white wire coming off of it that connects to the red/white on the harness. this is the ground. when you put a multimeter to the end coming off of the transformer, and test for continuity with the base of the transformer, do you have continuity? i am wondering if my transformer might not be getting its ground? but when i connect the black on the red/white and the red on the orange, purple, or red, i do get the correct voltages +12, +12 and +18

on the selt test switch, which direction is the self test mode and which direction is the game play mode? i forget...

coming off your +5 switcher, where do you have the 6 wires connected?
also, do you have a ground coming to the main ground on the ac input of the switcher? and where do you ground it?
 
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