• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Computer Moniter Power Supply Repair

Andy1845c

Active Member
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.
 

RODALCO

Well-Known Member
Check the fuse if it has any. Should be somewhere near the point where the mains lead enters the monitor.
 

Menticol

Active Member
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.
 
Last edited:

selvatrinity

New Member
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
 

mvs sarma

Well-Known Member
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.
 
Last edited:

Latest threads

EE World Online Articles

Loading

 
Top