Monitor interference caused by another game?

JamBurglar

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I recently did a monitor swap on my Q*Bert. I removed the original WG4900 and replaced it with another WG4900 that had a tube-swap done on it. The picture on the new, tube-swapped monitor is great, however, when I turn on the game next to it, I now get some interference.

Here's a pic
QBert%20WG4900%20Menu.jpg


The line shown moves from left to right over and over, towards the game that appears to be causing the interference.

The game to the right (the one presumably causing the interference) is a Vs. Unisystem running various Nintendo boards and a Sanyo EZ monitor. All the boards are in RF cages so I'm guessing the interference is being caused by the Sanyo.

I note that the old WG4900 did not seem to be affected.

Does anybody have any experience successfully eliminating this type of thing (aside from physically moving the cabinet to a different location)?

I was thinking about possible solutions (other than physically moving the cab) and came up with:

1) Swapping out the chassis on my new monitor with the original chassis (the old monitor didn't have this type of issue, however, if if this problem is linked to the TUBE, then the chassis swap would be pointless.

2) Buying a roll of RF shield and lining the inside left of the Nintendo cab with that.

3) Lining the right inside of the Q-Bert with the RF shield.
 
wrap them in aluminum foil....:D

are they plugged into outlets on the same circuit breaker? if they are see if you put them on different circuits whether you get any change.
 
As an experiment it would be interesting to see if you still get that interference with your monitor power cord unplugged in your vs. Unisystem cabinet. That would at least tell you if it's the other monitor or other game boards causing the issue.

Also, are you sure that all of your ground plugs were plugged back in correctly on your tube-swapped 4900?
 
As an experiment it would be interesting to see if you still get that interference with your monitor power cord unplugged in your vs. Unisystem cabinet. That would at least tell you if it's the other monitor or other game boards causing the issue.

That's a really good idea actually. I thought about unplugging the boards but really I can do both and try to figure out exactly what's causing the issue.

Also, are you sure that all of your ground plugs were plugged back in correctly on your tube-swapped 4900?

This is another great suggestion. I have the monitor in the Q*Bert grounded in the same way that my old monitor was, which is having the ground strap connected to the frame (I'm assuming that's right), but I don't know if there are other areas of weakness. I have my other monitor so I can also try to figure out where other ground points are. I can also check continuity from the monitor to the ground prong on my power cord.

Q*Bert can be a strange beast when it comes to grounding. I know a lot of people will remove the grounds in various places to deal with various bugs. I've kept all the grounding in mine though. I did temporarily remove the ground strap from the monitor to see if it affected the interference but that had no affect.
 
wrap them in aluminum foil....:D

are they plugged into outlets on the same circuit breaker? if they are see if you put them on different circuits whether you get any change.

Ha! I actually tried a sheet of foil between the games and then I did some reading on RF and realized that it was not going to be effective. Pretty sad!

I'll get an extension cord and try Q*Bert on a different circuit. Currently both games are on the same power strip.
 
Thanks for all the suggestions.

Just a quick update. It's definitely the Sanyo EZ from the Nintendo cab causing the symptom (or at least the WG4900 is extra susceptible to interference caused by an adjacent monitor). When I unplugged the Sanyo monitor from the Nintendo and powered up the Nintendo cab, the problem went away.

I also tried the games on different circuits and that didn't change the symptom.

I'm fairly certain the Nintendo cab is grounded well because I replaced the power chord in that one a few years back and ran continuity tests throughout. I note that the Sanyo is horizontally mounted in the Nintendo cab. The flyback does have the RF cage but it only runs around the sides and top, and it's the bottom of the flyback that faces the Q*Bert cab. There is a metal frame underneath the flyback but maybe that doesn't shield? Hmmm. I would think the metal plate below the monitor PCB would shield but maybe I'm wrong there. I'm not quite there yet though.

I'm thinking my next step will be to go through the Q*Bert and double-check to make sure everything is actually grounded, as demogo and HighScoreSaves suggested. There is definitely a ground plug on Q*Bert and I know the grounding to the boards is good because I worked through that in the past but I need to check the monitor in particular.

As far as I can tell (bear with me here I'm not all that educated in this area) the points of ground are:

(1) yellow strap to monitor frame.
(2) molex pin 4 to P202 on the monitor chassis (obscured by tube)
(3) molex pin 4 from J402 to P402 from neck board to monitor chassis (highlighted on schematic but on underside of neck board)
(4) black wire "E" on schematic from the neck board to the yoke (also shown in pic below, I think)
(5) Dag wire (shown below?)

I could be way off base.

QBert%20Schematic.JPG


*This is my original monitor, just using it for purposes of example:

Q-Bert%20Monitor.jpg
 
Are the line filters present on both machines?
 
I did some more trouble-shooting over the weekend.

First, unless I'm missing something, both cabs seem adequately grounded.

Following my list above, I checked continuity from the 3rd prong on the power cord to:

(1) the monitor frame,
(2) the monitor chassis,
(3) the neck board, and
(5) the strap around the tube (not the dag wire).

That all checked out.

I could not find any ground for the yoke (item 4 on my list). I double-checked my old monitor and saw no ground there either.

No change as far as the symptoms.

I also checked for line filters but I've really got no clue what I'm looking for here. Q*Bert's power line comes into the power brick and it's got that big ole blue filter cap. The Nintendo cab is stock. Is the line filter to the right of the transformer on these (on the power brick)?

Assuming nobody has any other ideas, I'll probably try to swap the chassis on the Q*Bert, and if that fails I'll buy a roll of RF filter material.

I guess I could always move the cabs but that's TOO EASY.
 
an original nintendo and qbert i have never seen a line filter separate in them like other games.
 
Still trying to figure this out without swapping the chassis.

One thing I noticed is the dag wire hookup is backwards from the way my original monitor was hooked up. Does the orientation of the red and green wires from the dag wire make a difference? If I reverse this connection will I harm the monitor?

Recap of symptom:

WG4900 Monitor (with recent tube swap)

Symptom is a scrolling shaded line that moves vertically across the screen over and over (this monitor is vertically mounted so it looks like the scroll is moving left to right but in actuality its moving vertically).

Symptom only occurs when the game next to it is turned on. It doesn't matter which game. Specifically, its the other game's monitor that triggers the interference.
 
Still trying to figure this out without swapping the chassis.

One thing I noticed is the dag wire hookup is backwards from the way my original monitor was hooked up. Does the orientation of the red and green wires from the dag wire make a difference? If I reverse this connection will I harm the monitor?

Recap of symptom:

WG4900 Monitor (with recent tube swap)

Symptom is a scrolling shaded line that moves vertically across the screen over and over (this monitor is vertically mounted so it looks like the scroll is moving left to right but in actuality its moving vertically).

Symptom only occurs when the game next to it is turned on. It doesn't matter which game. Specifically, its the other game's monitor that triggers the interference.

the red/green wire is from your deguass coil and not the DAG wire. the dag wire is connected to the metal band that is strapped to the tube making contact on the aquadag and should have a black wire going to the neck pcb. your red green wires are going to the main pcb and that is your deguass coil and either way installed won't matter.
 
the red/green wire is from your deguass coil and not the DAG wire. the dag wire is connected to the metal band that is strapped to the tube making contact on the aquadag and should have a black wire going to the neck pcb. your red green wires are going to the main pcb and that is your deguass coil and either way installed won't matter.

Got it. I've never done much with the tubes before so I'm totally oblivious.
 
I've narrowed this down a little further.

I've got a PCB switcher in the Nintendo cab and when I've got Popeye running there is no interference. The only time I get interference is if a Vs. game is running. Also, all Vs. games cause the interference (I think I've tested 6 so far).

I've ruled out the PCB switcher by connecting the harness directly to the PCB (still get interference).

I don't think its the harness because the same harness is used for both Popeye and the Vs. games.

I've also swapped the monitor chassis for the WG 4900 in the Q*Bert that is being affected. No difference.

So far it seems like something with the Vs. PCBs is triggering the interference. From what I can gather so far, I think it's something between those Vs. PBCs and the replacement tube in the 4900.

My Dragon's Lair will also cause the interference so maybe Dragon's Lair and the Vs. games are running at a frequency that doesn't play well with Q*Bert but Popeye is running at a frequency that is okay.

Everything is grounded and I've even experimented with completely removing ground and there has been no affect.

I do have the Vs. PCBs in cages, but they are not fully enclosed and I'm not running the filter boards for the Vs. cages.
 
Still can't pin this down. Putting Q*Bert next to my Nintendo cab running a Vs. game or next to Dragon's Lair causes the interference. If I get the games about 3 ft apart it goes away. If I run Popeye in my Vs. cab (same harness, same CP, same everything as the Vs. games with the exception of the PCB) the interference stops. No interference if I put Q*Bert right next to Donkey Kong either. Removing/adding grounding seems to have no effect.

Does anybody know a good source for RF blocking material (looking for something that comes in a roll). I think I'm going to try that next.
 
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