Qbert fuse question

kelleyphd

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Hi All,

I have a Qbert that is playing blind and is blowing F3 (the fuse for the monitor) immediately when plugged in. I tested the voltage there and get 128VAC. Obvious questions but is this too much for the fuse? If so, any way to lower the voltage? - it comes directly from the transformer. I do not have the monitor hooked up so I know it isn't a monitor issue.

Thanks
Daniel
 
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128VAC should be just fine. The manual for the WG K4900 (which appears to have been OEM in Q*Berts, not sure if yours still has the original monitor or not...) says it's designed to work with anything between 108 and 132VAC. I'm pretty sure the voltage isn't the source of your problem.

It may or may not be a monitor issue. If your wiring is original, the monitor shares a circuit (and fuse F3) with the marquee. It's possible (but not particularly likely) that a short in the marquee is blowing the fuse.

In the monitor itself... a couple of the usual suspects are:
-the degauss coil; try unplugging it and see if it still blows the fuse
-the bridge rectifier; a DMM with diode-check can be used to fully test the bridge (see "testing bridge rectifiers" half-way down this page: http://www.pinrepair.com/begin/index.htm)

It could be other things in the monitor, but these are among the easiest to check, and digging deeper would require knowing the monitor model.
 
It may or may not be a monitor issue. If your wiring is original, the monitor shares a circuit (and fuse F3) with the marquee. It's possible (but not particularly likely) that a short in the marquee is blowing the fuse.
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A marquee ballast cpuld cause this.

Edward
 
128VAC should be just fine. The manual for the WG K4900 (which appears to have been OEM in Q*Berts, not sure if yours still has the original monitor or not...) says it's designed to work with anything between 108 and 132VAC. I'm pretty sure the voltage isn't the source of your problem.

It may or may not be a monitor issue. If your wiring is original, the monitor shares a circuit (and fuse F3) with the marquee. It's possible (but not particularly likely) that a short in the marquee is blowing the fuse.

In the monitor itself... a couple of the usual suspects are:
-the degauss coil; try unplugging it and see if it still blows the fuse
-the bridge rectifier; a DMM with diode-check can be used to fully test the bridge (see "testing bridge rectifiers" half-way down this page: http://www.pinrepair.com/begin/index.htm)

It could be other things in the monitor, but these are among the easiest to check, and digging deeper would require knowing the monitor model.

Thanks for the info. I disconnected the monitor and it still blows the fuse. But the monitor is the original eg4900. I will check on the marquee for a short.

Daniel
 
A marquee ballast cpuld cause this.

Edward

BINGO. Not sure it is specifically the ballast but unpluging the lamp assembly solved the problem. Thanks for the help.

Any way to test a ballast? And how do I determine the wattage for a replacement. Does it just go off the bulb?

Daniel
 
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BINGO. Not sure it is specifically the ballast but unpluging the lamp assembly solved the problem. Thanks for the help.

Any way to test a ballast? And how do I determine the wattage for a replacement. Does it just go off the bulb?

Daniel

If you've got a standard 18" fluorescent fixture in it....The replacement ballast will be rated at 14-20 watts. It should be mounted by or on the fixture. It's a square looking transformer. A good on will read around 24 ohms.

Edward
 
It's possible (but not particularly likely) that a short in the marquee is blowing the fuse.

Looks like I mis-estimated those odds :)

Bob Roberts has a nice pic of generic marquee wiring: http://www.therealbobroberts.net/fluor_circuit.jpg

He shows 26ohms for a good 14-20W ballast, nearly the same as Ed says.

Around here, Home Depot sells appropriate replacement (GE branded) ballasts for like $6.
 
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