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Computer Moniter Power Supply Repair

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Andy1845c

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Just kind of a shot in the dark, but my 5 year old CRT moniter died the other day. I wasn't home when it happened, but my wife said she turned it on and nothing happened, no pop or flash on the screen. I dosn't do anything now. I can't even get the power indicator LED to light. I was hoping the fuse just blew, but that checks out okay.

There is a small relay on the board. I can activate it with a 9v battery, so I am pretty sure the mechanical part of that is okay. Past that, I don't really know what to look for. I don't see any burnt components or anything visibly wrong. I am assuming that the failure is in the power supply side of things, since the relay won't click with the switch and the LED is not lit. I see a small transformer that appreas to have several taps and some dioides that appear to be arranged as a bridge rectifier.

I don't remember the brand (I'm at work atm). Its from an E-Machines computer setup. Doubt it matters anyway unless someone knows where I could possibly find a schematic.

I know its at the end of its useful life, but I thought it would be cool to be able to repair it and thought maybe someone here knows of a common fault I could investigate.
 
Check the fuse if it has any. Should be somewhere near the point where the mains lead enters the monitor.
 
I don't know what kind of monitor do you have Andy, but I hope this helps

1) If it's an old model with the classical On/Off switch (I mean, the switch is connected in series between mains and PSU), check the switch and the wiring

2) If is a newer model with a small switch that sends a signal to the PCB and turns on the thing, do the following:

a) Check if the button is actually working (I guess it's a N.O. switch)
b) If the monitor finally starts after pushing the button >30 times, the PSU electrolytic capacitors are definetively bad, change them
c) If it doesn't, find a 7805 regulator near an EPROM, the bigger one near the PSU. Check if it's giving +5V.

That 7805 feeds the processor (don't know the name in english) that waits for your order of turning ON the monitor while it's on Standby mode.
 
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hi all,

i have compaq 7540 model crt monitor.

now the problem is the memory ic fault. how to restore it.

please tell me

thanking you

yours lovingly,
selvkumar.v
 
hi all,

i have compaq 7540 model crt monitor.

now the problem is the memory ic fault. how to restore it.

please tell me

thanking you

yours lovingly,
selvkumar.v
Straight diagnosed to the memory? any indications for this conclusion? what is that chip number and i wonder if, it is eprom, it might have some data resident.
 
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