PC monitor does not turn on

Nigel Goodwin · May 10, 2021

JMaia said:
Can you explain in more detail about those balancing resistors? How to install them, and which ones to buy?

Just low value resistors in series with each diode, 0.22 ohm should be fine.

BTW, when unsoldering the legs, apply fresh solder to help the old solder melt, it makes it a LOT easier - perhaps you already do that?.

JMaia · May 11, 2021

Nigel Goodwin said:
Just low value resistors in series with each diode, 0.22 ohm should be fine.

So I went to a eletronic store and bought the diods and the resistors, but the lowest they had was 0.27 and they look different than normal resistors:

Will these work? Do I have to install them together and in the same holes as the diodes?

sagor1 · May 11, 2021

You have to install them in series with the diodes. That is, one end of the diode in the original hole. Other end of diode to one leg of the resistor, up off the board (and insulated if possible). Other end of resistor goes into the other original diode hole.
You can reverse the order - resistor first in one hole, then diode joined to resistor, then other diode leg into board. It does not matter which order you put them in, as long as they are in series. That all said, I hope those are at least 5W resistors.

Nigel Goodwin · May 12, 2021

sagor1 said:
You have to install them in series with the diodes. That is, one end of the diode in the original hole. Other end of diode to one leg of the resistor, up off the board (and insulated if possible). Other end of resistor goes into the other original diode hole.
You can reverse the order - resistor first in one hole, then diode joined to resistor, then other diode leg into board. It does not matter which order you put them in, as long as they are in series. That all said, I hope those are at least 5W resistors.

It's not as bad as you might think - because of the low value of the resistors the dissipation is relatively low, those are pretty substantial resistors, so more than big enough.

JMaia · May 12, 2021

sagor1 said:
That all said, I hope those are at least 5W resistors.

I read on the receipt, they are 5W.

How should I solder the legs to one another (resistor to the diod). Tried to google a guide but didn't find any.

EDIT: Ok so i tried to solder the stuff and I did a spetacular bad job at it. I think I managed to solder 2 holes properly, but the other 2 the solder just wont stick to the hole, I think they it may be flux that is attached to the board:

Any idea on how to clean this up? I tried a toothbrush an alchool but i wasnt able to remove the yellow gunk.

EDIT 3: Itried to turn on the monitor even with the components not properly soldered, it worked!!!!

sagor1 · May 13, 2021

Hard to tell from the picture. Are you using good rosin core solder? Is the iron hot enough? I would suspect at least a 35W to 45W iron would be good for that size of wire. But, don't heat the solder pad on the PCB too much, it may lift and peel off.
If it does not "stick", it may be that you damaged the hole when you removed the diodes. You may have pulled out the via between the top and bottom. As long as you solder the top and bottom pads, the wire will serve as a conductive via still...

Diver300 · May 13, 2021

Nigel Goodwin said:
No point with a capacitance meter - if you want to check it you MUST use an ESR meter, as they fail low-ESR if they are going to fail. A capacitance meter would almost certainly check it as OK, even if it was faulty - unless it does ESR, in which case it's an ESR meter.

I think you mean that they fail due to the ESR going higher.

Nigel Goodwin · May 13, 2021

Diver300 said:
I think you mean that they fail due to the ESR going higher.

Well spotted, high-ESR of course.

JMaia · May 13, 2021

sagor1 said:
Hard to tell from the picture. Are you using good rosin core solder? Is the iron hot enough? I would suspect at least a 35W to 45W iron would be good for that size of wire. But, don't heat the solder pad on the PCB too much, it may lift and peel off.
If it does not "stick", it may be that you damaged the hole when you removed the diodes. You may have pulled out the via between the top and bottom. As long as you solder the top and bottom pads, the wire will serve as a conductive via still...

I used a 60 w iron. I dont know if the solder is any good, but probably not, it's the cheapest you can buy on ebay from China.

Anyway, the diods seem fixed enough, so I tried to assemble the monitor and all works all right. In fact, I'm using it right now.

Thanks for the help guys. It's crazy that I managed to fix this using only 2 electronic components that cost 2 euros.

Nigel Goodwin · May 14, 2021

JMaia said:
I used a 60 w iron. I dont know if the solder is any good, but probably not, it's the cheapest you can buy on ebay from China.

Anyway, the diods seem fixed enough, so I tried to assemble the monitor and all works all right. In fact, I'm using it right now. View attachment 131360

Thanks for the help guys. It's crazy that I managed to fix this using only 2 electronic components that cost 2 euros.

As I mentioned above, it's a VERY common failing, basically due to a serious design flaw (the missing resistors).

benstrom531 · Mar 11, 2022

If another monitor works on the same cable then there is a fault in your monitor but if the other one computer did not work Try connecting the monitor with a different video cable. If the monitor still does not work ,Replace the monitor power cable . Replace or service the monitor if it still does not turn on. If this does not fix your monitor then buy a new one .

JMaia · Mar 12, 2022

benstrom531 said:
If another monitor works on the same cable then there is a fault in your monitor but if the other one computer did not work Try connecting the monitor with a different video cable. If the monitor still does not work ,Replace the monitor power cable . Replace or service the monitor if it still does not turn on. If this does not fix your monitor then buy a new one .

The monitor is already repaired

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