K7000 sync, then ground issues

Where is your -V sync? You either need to run -H and -V to the right pins, or if you're doing composite sync, you need to tie -H and -V together.

I'm pulling video sync off JAMMA to chassis's last pin, -H sync. I've also tried just -V sync, and both of them. Many times. : )
 
In my experience, Insurance is only good if you can prove it was damaged in shipping. Unless the box is badly damaged, you'll have a hard time collecting.

Seller was willing to exchange chassis if we can't figure it out, but as two games I've tested DID sync, I'm presuming the issue is something I'm doing wrong, and not necessarily the chassis.
 
I spoke with Mecha this afternoon who reached out to me (how cool is that?). A couple of things he considered red flags:

1) That when I ran earth ground directly from switching PS to monitor frame, the chassis fuse blew. Thinks something is up with my AC setup. Could very well be. But all in all it's a simple area, and I keep looking at it and reading and jus really unsure what could be wrong.

As mhkohne said in a previous thread, "Earth ground (the third prong on the AC cord and the case of the power supply, and probably what you should be grounding the monitor frame to) is NOT the same as logic ground (found on the black wires of the JAMMA harness). If you tie the two grounds together (or try to use the wrong one), you'll create problems." All along folks think I have a ground issue, and boy that sounds right, but what/where/how? I also finished that 3-page thread and nobody can seem to agree on whether FG should ever touch logic ground.

2) That when I remove sync from the chassis I just see black instead of a wavy image.

He also suggested that I reflow some points on the chassis, which I'll try next.
 
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Haven't been able to work on this due to the rains in Northern California -- my workshop in the basement floods pretty easily. When I return to it I think the focus will be on ground and FG.

Unfortunately during testing I seem to have messed up a couple games which I'll post about in another thread to see if they're goners.
 
if by applying earth ground to the frame of the monitor blows the fuse then you dont have a properly installed isolation transformer in front of the monitors AC supply.

An un isolated monitor will blow open the video ground trace on a logic board in a heartbeat. Some boards seem to be able to deal with it (probably an isolated GND on the board) and some not (that arcadeSD for instance).

You need to correct that before you move on.

Once you correct that check the boards that wont SYNC, you will probably find that their video GND traces are blown open.

FWIW, you can attach earth GND to logic GND. In many cases doing so actually gets rid of noise on teh screen that some switching power supplies create.
 
Update:

1) Someone pointed out to me that you can't measure any possible voltage coming into the monitor frame by clipping on to it and the switching PS ground, so that 109v ac I was getting was incorrect.

If I'm reading this right you measured 109VAC between the frame of the monitor and the GND on the power supply???

That should be WAY closer to zero. Like less than 10 volts AC probably.

Fix that ISO!
 
if by applying earth ground to the frame of the monitor blows the fuse then you dont have a properly installed isolation transformer in front of the monitors AC supply.

An un isolated monitor will blow open the video ground trace on a logic board in a heartbeat. Some boards seem to be able to deal with it (probably an isolated GND on the board) and some not (that arcadeSD for instance).

You need to correct that before you move on.

Once you correct that check the boards that wont SYNC, you will probably find that their video GND traces are blown open.

FWIW, you can attach earth GND to logic GND. In many cases doing so actually gets rid of noise on teh screen that some switching power supplies create.

This seems to be the key, that my iso trans is incorrectly wired in some way, but I don't see how. What if it were backwards? The four lines are coming from nearly the same location so it's hard to distinguish.

If those blew the video ground traces on those games, that would make sense. Looking over both with magnification though I'm not seeing that. I'll test with multimeter, but would be easier if I had schematics of the boards, as I'm not sure I see where the ground traces are running.

If I'm reading this right you measured 109VAC between the frame of the monitor and the GND on the power supply???

That should be WAY closer to zero. Like less than 10 volts AC probably.

Fix that ISO!

That reading came from connecting multimeter to monitor frame and PS logic ground, which I was subsequently told is an incorrect way to read voltage coming off monitor frame. I'm unsure how to measure this.
 
That reading came from connecting multimeter to monitor frame and PS logic ground, which I was subsequently told is an incorrect way to read voltage coming off monitor frame. I'm unsure how to measure this.

While it may in fact be incorrect it is a way to see if your monitor is properly isolated or not. When it is that same procedure will net you a low voltage measurement. If its high (like what you ended up with) then there is probably something wrong (as in ISO is not in circuit).
 
While it may in fact be incorrect it is a way to see if your monitor is properly isolated or not. When it is that same procedure will net you a low voltage measurement. If its high (like what you ended up with) then there is probably something wrong (as in ISO is not in circuit).

When the rains let up -- probably not a good idea for me to play with the monitor while standing in an inch of water -- I'll entirely rewire the AC and document along the way.
 
Starting a bit fresh as I removed all wiring except for AC. Replaced isolation transformer -- long shot, but just in case. Other than getting 130v out of it, it seems fine. Next I added field ground -- this is going from AC ground into the filter, then connecting side of filter with foot of isolation transformer, then up to field ground on power supply. Getting steady readings, all good there.

Connected AC coming out of isolation transformer to monitor chassis. Getting steady image on screen (which I have been in the last few tests), but can still hear this faint almost sizzling noise, like the electricity is jumping around in the tube. A couple times I heard a slight electric snap on the monitor chassis. These are very faint and almost seem normal, but not quite. These results are the same as last time I tested several weeks back.

In my notes I had written down what someone said in a different thread about dealing with a short, "You could try unplugging the degauss connector. If there is a short in the degauss wiring, it could be shunting electricity to the frame." Turned off, unplugged degauss connector, turned on and the faint sizzling noises and occasional pop disappear! Not sure how to go about finding where the short is on the degauss wiring wrap, how to fix, or whether I should just leave unplugged.

Next I try connecting field ground to monitor frame, which was previously blowing the chassis fuse. It works fine, no blown fuses. Assume because the degauss wiring isn't connected to the chassis.

At this point I think I've isolated the issue, but after another 5 or 10 minutes of letting it run and taking in the wonderful silence, a new noise starts which I've never heard before. It sounds like a motor running, and when the power is turned off, slows to a stop like a motor, oddly enough. This is happening whether field ground is connected to the monitor frame or not btw. In fact nothing seems to stop the noise. I tried adjusting the anode cup a bit, wondering if it was coming off, but it seemed just fine, and once powered back on the noise went away, then started again after a couple minutes. Turned off for 30 seconds, turned back on and the noise just starts up again.

http://jessiejohnson.net/arcade/2017-03-11-k7000-sound.m4v

About to just cut my losses and find another 19" monitor for this project.
 
After someone suggested the anode cup may not be on tight, I removed it and slid cup further down, now the flat plate sits nicely against the hole in the crt. Powered on and last of the strange noises went away! Let it run for an hour with no problems. Craziness that this was one of the last issues.

Ran ground throughout cab and up to monitor frame, also without issue.
 
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