WG267126 Powering issue

AtariShag

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I am having an issue with a WGK7000 monitor (from an MKII cabinet) that I need some help with.

Quite a while ago the monitor started having an issue where it would only power up when you turned it on and off multiple times. Eventually it just gave up completely. I replaced the flyback, the HOT, most of the caps and it was still no good so I took it into my distributor where they fixed it and sent it back. They didn't tell me what they did to it, but it worked. But it only worked for a few months and while someone was playing a game on the cabinet, the image suddenly went out. I turned the cabinet off, then back on and the image stayed for a short time then it turns off again. Now the monitor won't power up no matter how many times I turn it on and off but even if it did I'd like to figure out what's going on with it.

I checked the voltage from the power source where it connects to the chassis and I get a rating of around 130 using the 200 Vac setting on my multimeter (apologies as I am a noob with this stuff still) but I'm not sure if that's good or bad.
 
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WG267126 is the serial number of the chassis, not the model. Check the monitor ID page on Bob Robert's site and see if any match your model...
 
Could be several problems, but if your fuse is still good, you most likely have some cold solder or broken traces in the power area directly behind the flyback...
 
Yes the fuse is good. I checked the HOT too just to be sure and it checks out ok. I tested the diodes in the power area and they all checked out fine too. I will check the solder and hopefully that is all it will be.
 
Here's a followup:

I pulled the board and checked the solder in the power area - there was some cracked solder there and in a few other places, I fixed that up with some new solder and plugged everything back in and the monitor turned on just fine. It ran for a few hours, three or four but then the image suddenly went out again and it won't come back on.

Could a component be overheating, causing the solder to crack or become unstable or just a component itself failing here?
 
Possibly. You may want to go over that section again. I've often thought i fixed all the bad spots, had a monitor work just fine, then the next day not work again and I'd pull it out and find a few more spots to fix. Usually you'll see your B+ running about 160 when this happens. When I fix it, I don't just use new solder, as the traces tend to break loose at the component holes. I save clipped capacitor legs and use them as bridges from one component to the next on the trace. If i need to jump farther, or if I come to close to a point not on that trace, then I use insulated wire with the ends stripped a little, tinned, and soldered to the board.

You should test your VR (IC4), too, just in case...
 
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Possibly. You may want to go over that section again. I've often though i fixed all the bad spots, had a monitor work just fine, then the next day not work again and I'd pull it out and find a few more spots to fix. Usually you'll see your B+ running about 160 when this happens.

You should test your VR (IC4), too, just in case...

Thanks, I'll check the points again. There is a spot right under one of the pins on the large capacitor where part of the circular trace is broken off too so I wondered if that might have something to do with it.

Sorry to ask this but which part would be the VR IC4 and what's the best way to test it?
 
IC4 could be one of four different parts, depending on your monitor size:

19" - STR3123 or STR30123
25" - STR3130 or STR30130

The two for each size are NOT interchangeable, as they are different sizes and have different number of legs. Check to see which one you have, and if you need to replace it, get the same one.

You check it for shorts using your multimeter set to diode test. Test with the black lead on each leg and the red lead on each of the other legs. Do all combinations. Anything that is all zeroes (or you get a beep) means you need to pull it and test again. If still shorted, then replace it (remembering to keep the mica insulator between it and the wall in mounts to...)
 
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