Do we have any electronics experts on here?

Diddums

Diddums

Diddums

Caporegime
Joined
24 Oct 2012
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Yer nan's knickers
My monitor's PSU went pop, resistor exploded. I need someone to fix it mainly because I don't trust my soldering ability enough to not screw it up. I will offer some beer tokens in exchange, and yes I could go to a proper company but why not offer someone a way to make a quick buck first. I will post it to you and pay for everything. I understand that this is not guaranteed to sort the monitor but rather than ***** a load of cash on a new one I need to give it a shot first (also because I LOVE this monitor and they are discontinued). You'll need to source the resistor too because I have zero idea where to get these things from. All payments will be made up front and I will only offer this to someone who I trust, so noobs need not apply.

It's this one:

b5oWqdg.jpg


(mods pls delete if not allowed).
 
Rroff said:
Was a thread about this that was almost identical recently?

If you are talking about the green components they may be inductors rather than resistors given that two of them have been damped. What looks like a diode seems pretty funky as well possibly not just residue on it.

EDIT: Ah yeah thought I recognised that layout

https://forums.overclockers.co.uk/threads/pcb-repair-soldering.18807426
Click to expand...



Yep, same one. I've left it but now I want it fixed. If someone can point out the type of resistor and where I can get one maybe I'll give it a go.
 
Diddums said:
Yep, same one. I've left it but now I want it fixed. If someone can point out the type of resistor and where I can get one maybe I'll give it a go.
Click to expand...

I've repaired my own guitar amps and psu when it went pop. It's really not as hard as you think..... but you'll obviously have to identify the correct part. You can most likely then find it for pennies on ebay.... I for example had issue with my mouse middle clicker was broken, got new one 5p on ebay instead of 60 quid for a new mouse (razer deathadder). I replaced and soldered the part, job done.
 
are we talking about the black component with long legs in the middle of the shot?

because the symbol below it on the pcb looks very much like a diode to me.

also do not trust my advice, me and diodes have a recent history of making explodey things happen.
 
If its what the out of focus component what I think it is, clip it as close as you can to the component and solder a replacement on to the old connectors, saves you messing with the PCB. ;)
 
The silkscreen on the PCB confirms it is a diode. As it is is mounted way above the PCB this diode is designed to get warm. Can't quite make out the designation but it's likely to be shottky diode.

As for failure reason could be simply a poor design, lack of cooling or underrated component. Nothing else seems to have cooked, however there may be an issue we can't see.
 
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Tealc said:
The silkscreen on the PCB confirms it is a diode. As it is is mounted way above the PCB this diode is designed to get warm. Can't quite make out the designation but it's likely to be shottky diode.

As for failure reason could be simply a poor design, lack of cooling or underrated component. Nothing else seems to have cooked, however there may be an issue we can't see.
Click to expand...

From the pictures/comments in other thread, it looks like the issue is with the green component, not the diode, i.e.:
Feek said:
3N7L2MY.png
Click to expand...

Diddums, if you've got a multimeter, it might be worth quickly checking for a short on (what I assume are) the two transistors attached to the heatsink close to it. If either are shorted (which is a possible cause of the resistor blowing up), just replacing the resistor won't be enough.
 
Ah the inductor. Yes remember that discussion from a while back. The inductor and diode sit on the output of the switching power supply to would be hit pretty hard if the transistor did fail.

I'd replace the inductor, the diode and probably the transistor too.
 
Swanster said:
Diddums, if you've got a multimeter, it might be worth quickly checking for a short on (what I assume are) the two transistors attached to the heatsink close to it. If either are shorted (which is a possible cause of the resistor blowing up), just replacing the resistor won't be enough.
Click to expand...

Checking the transistor is functional would require a bit of knowledge of what type of transistor (could also be a mosfet, shunt or voltage reference, etc.) it is and how to check.

Its also possible (depending how it is used) that the diode has failed closed due to a reverse voltage surge or something of that nature taking out the green component so as some have noted it might not be enough simply to replace the visible damaged component(s).
 
Well I am a highly qualified and skilled electritian who they let work on aircraft.


I haven' soldered anything with anything other than a massive heat gun in years and I have no idea when it comes to electronics but I'm willing to give it a go when in london!


I'll even throw in some mild molestation too.
 
Rroff said:
Checking the transistor is functional would require a bit of knowledge of what type of transistor (could also be a mosfet, shunt or voltage reference, etc.) it is and how to check.
Click to expand...
Oh, sure, it could only confirm it's bad; I agree confirming it's good would require much more information and effort (and removing it).
But checking if it's shorted is easy, and could tell you straight away if you've got bigger problems than just a resistor. Limited experience tells me these things can go 3-way shorted, which is dead easy to spot.
 
I would initially suspect the big black electrolytic capacitor on its side in the middle of the board. That'll be the main smoothing cap for the DC rectified mains for the switch mode power supply. You need test gear to check the ESR of the caps. Most failures of the type you show in SMPS's are down to ageing / poor electrolytics.

Be aware SMPSU's have over 300V DC on the caps and some retain this charge for long periods. 300V DC is enough to give you a damn good belt, or worse if you are unlucky.
 
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