General Monitor Troubleshooting

claysred

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I'm still quite a newbie on monitors in my opinion. I can install a cap kit and even a HOT or flyback, however, it's just replacing parts. I want to be able to test using the schematics and replace the bad part, not all of them.

Although I have several questions, I'll keep it short. How can one test the power supply of any monitor? Let's take a WG U5000 for example. After reviewing the schematic, I see the a/c comes in at CN101. It goes through a choke (L101), some caps and resistors, then through a bridge diode (D101-D104) and that's where I get lost. I know that somewhere in there, I need to measure the b+, but where??

Next, if there is not a b+ voltage, then I should lift some component and hook up a load tester and then test the b+ to see if the power supply section is working correct?

I just need a little coaching here guys!

Thanks in advance.
Clay
 
Measure B+ at the banded end of diode 101 or 102 with respect to ground.
If it's missing from there it's fairly easy to troubleshoot.
If the fuse is not blown then check for approx 120 volts A/C between the banded ends of D103 and D104. if it's there then you most likely have an open diode.
If the fuse is blown you likely have a shorted diode.
Your meter can tell you which diode is faulty.
It's rare that R101 or L101 will open, but you can check those if a bad diode doesn't turn up, but you'll be missing the 120 volts A/C if this is the case.
Now as to why a diode will fail.... that's another thing altogether.
 
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