Fuses repeatedly blowing

beef

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Hi Guys,

Long time reader, I think second time poster.

I am having an issue with one of cabinets that I need help figuring out. I have a monitor that keeps blowing a fuse (or sometimes both) whenever I turn it on. This particular cab I got as project and has never worked. I couldn't see anything wrong with the original chassis hooked up to the monitor, but my skills in that area are limited. I ended up trying to swap the chassis hoping that would help with the issue. However, the same thing happened.

When I put the new chassis in, the monitor turned on and I could start to see the picture light up, and then it went blank.

Seeing as the same issue happened with both chasses I am starting to thing it is something wrong with either the power coming in, or the tube. However, I am at a loss of where I need to start looking next.

Thanks.
 
Is the monitor being powered by an isolation transformer? We also need to know the make and model of the monitor....to help you more. Post a picture if unsure (a picture of the chassis, not the tube).

Edward
 
Also, when you swapped the chassis, did you replace it with the SAME chassis? You can't just go mixing and matching chassis with yokes, they need to be designed to work together.

But, to echo what others have said, we need more information. Like,what kind of monitor is it, what game is it, is it hooked up right, etc. Pictures would help. We can't just go off "it blows fuses. This one too". Imagine telling a mechanic "My car makes this funny sound. Tell me how to fix it" ;)

-Ian
 
I do not know if the monitor is powered by an isolation transformer. The cabinet is a capcom Q25 and has custom power supply in it that I have not seen in an other machine. The monitor power comes right off of that.

The original chassis was Nanao, but I don't have the model number handy.
The other chassis is a lesser known brand.

I will post the model numbers later tonight when I get home.

Thanks.
 
I do not know if the monitor is powered by an isolation transformer. The cabinet is a capcom Q25 and has custom power supply in it that I have not seen in an other machine. The monitor power comes right off of that.

OK, if the cabinet has been hacked up, you need to be sure that the monitor power is isolated. Unhook it from the monitor, and unplug the game. Use your meter to test continuity between the blades on the power plug and the pins in the monitor molex. If it's isolated, you shouldn't get any continuity at all. Some very new monitors don't require an isolation transformer, but all the old ones do. I am not at all familiar with the Capcom Q25 - is that some kind of generic cab, like a Dynamo or something?

The original chassis was Nanao, but I don't have the model number handy.
The other chassis is a lesser known brand.

This could be a big problem. In general, the deflection yoke on the tube is specific to the exact model of monitor it came from. Wiring it up to another chassis, designed for another yoke/tube could cause everything from an incorrectly sized picture to violent destruction of the output transistors. You'll have to double check to be sure that the new chassis is actually compatible with your yoke.

-Ian
 
Thank's for the info Ian. I will check the power once I get home this evening. As well as provide more information about the chassies and the tubes.
 
Also, some Nanao's are 100vac chassis, and will die if connected to 120vac. A step-down iso usually does the conversion...
 
Sorry for the delay.

The original chassis is a MS8-25FTB (at least I believe that is what the faded label says). On the tube the number MS8-25FBC is listed.


IMG_0031 by elreod, on Flickr

The new board is a Wei-Ya Model 429H.

IMG_0023 by elreod, on Flickr

I need to borrow my friend's discharging tool before I try to take it out.

The CRT is a Toshiba A59JMZ193X.

This is what the inside of the bottom of the cab looks like with the power supply and the audio amp. The big box on the bottom is the power supply.


IMG_0019 by elreod, on Flickr


IMG_0020 by elreod, on Flickr

As suggested I tested the prongs on the power cable and to where the power plug on the monitor goes in. When both the cab, and the power supply switches are on I get connectivity. So it sounds like I need an isolation transformer?

Thanks again for all your help guys.

Brett
 
Any thoughts?

In doing a bit more research, could it be the degauss coil?

The degaussing coil is not your problem. You need an isolation transformer, and you need to replace all of the power supply components in the monitor chassis that you have destroyed by plugging it in without an isolation transformer. Check the input rectifier diodes and main voltage regulator IC. They're probably shot.

-Ian
 
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