# Forum Home Renovation Television, Computers & Phones  Very hot monitor power supply

## Moondog55

I'm using an LG monitor with a separate PSU
I'm on my second PSU now and they are no longer made and none available it seems.
Same as the Samsung and same issue there.
 The last one seems to have died from too much heat as the plastic box was slightly deformed. I'm wondering if putting some sort of heat sink with radiator fins to the plastic box would help its working life?
At the moment it's hanging off the wall suspended by the cords to maximise airflow around it rather than sitting on the desk covered with papers and bits of junk. I could rustle up a small computer heatsink and some thermal grease if it would help with longevity

----------


## droog

I doubt an external heatsink will help much in this case.
Heatsinks should be connected to the source of the heat, either the iron core if it is transformer based or the semiconductors if it is switchmode. The plastic case will isolate the heatsink from the source and I would expect the internal temperatures to remain very similar.

----------


## Moondog55

> I doubt an external heatsink will help much in this case.
> Heatsinks should be connected to the source of the heat, either the iron core if it is transformer based or the semiconductors if it is switchmode. The plastic case will isolate the heatsink from the source and I would expect the internal temperatures to remain very similar.

  In which case the aluminium fins will help with stand-off from the wall and may be worth doing that, PSUs are cheap and readily available but the damn thing uses a nonstandard plug size. The computer shop tried a few alternatives too but all to sloppy a fit apparently. 
I really dislike non-repairables that seem to be deliberately made to fail early

----------


## Moondog55

Hmm Even without any thermal grease there is some transfer to the small heatsink and it's a bit cooler, it's interesting and I'm going to play around some more as I have a few of these old extrusions around, chuck out bin at Jaycar; old 486 chip coolers.

----------


## PaulDW

> "rather than sitting on the desk covered with papers and bits of junk. "

  Is that what happened to the 1st one? If it is out in the open and not covered up it could feel hot but most people overestimate how hot. Mid 40s°C is the limit most can hold onto.

----------


## Ozcar

> The computer shop tried a few alternatives too but all to sloppy a fit apparently.

   If you are going to replace the overheating power supply you already have one plug that fits (two if you did not throw the first failed power supply away). Can't be that tricky to join a couple of wires?

----------


## Moondog55

> Is that what happened to the 1st one? If it is out in the open and not covered up it could feel hot but most people overestimate how hot. Mid 40s°C is the limit most can hold onto.

  Conjecture on my part. but with the heat sink attached to the PSU it is much cooler, no doubt due to better airflow around the unit rather than transfer to the added mass. I can hold something that's around 50C with no problems but if I get a chance I'll put the heat probe onto it and get an approximate reading.
As for changing the plugs from the old one I have no idea what the polarity is or I'd do something for when this one dies.

----------


## InsaneAsylum

> If you are going to replace the overheating power supply you already have one plug that fits (two if you did not throw the first failed power supply away). Can't be that tricky to join a couple of wires?

  spot on here, cut the low voltage side cable with the plug and source a power supply with the same rating, then solder the low voltage cable and plug to the new power supply's low voltage side.

----------


## Moondog55

But if I do that; and it is a very simple job; what about polarity?
I was told by the computer shop that polarity of supply was important with these LG monitors and it isn't marked on either the supply or the input.
I didn't think to ask to keep the old PSU with attached integral output cable

----------


## droog

> But if I do that; and it is a very simple job; what about polarity?
> I was told by the computer shop that polarity of supply was important with these LG monitors and it isn't marked on either the supply or the input.
> I didn't think to ask to keep the old PSU with attached integral output cable

  
Do you have a close up picture of the socket and any markings ? polarity is often marked.
Or a model number for the monitor.
The computer shops I have visited I would not trust to have any idea on this level of detail how to read it from the markings. 
Edit: After a quick google LG appears to like 19v but various current ratings and centre positive connections. Of course your model could be different so check before taking this generalization and plugging it in.

----------


## Whitey66

Do you have a multimeter moondog ? If not, do you have a spare old speaker kicking around? (I suspect you would have as you're always talking about speaker enclosures  :Smilie:   ) 
If the speaker has the + and - marked on it you can connect it to your power supply to see if the cone moves out or in.
If you connect + on speaker to + on power supply the speaker cone will move outwards (you have to connect the negative also of course), if you have + to - it will move inwards.
Most monitor and laptop plugs with a cylindrical connector with an external and internal connection have the positive on the inside of the connector.

----------


## Moondog55

> Do you have a multimeter moondog ? If not, do you have a spare old speaker kicking around? (I suspect you would have as you're always talking about speaker enclosures   ) 
> If the speaker has the + and - marked on it you can connect it to your power supply to see if the cone moves out or in.
> If you connect + on speaker to + on power supply the speaker cone will move outwards (you have to connect the negative also of course), if you have + to - it will move inwards.
> Most monitor and laptop plugs with a cylindrical connector with an external and internal connection have the positive on the inside of the connector.

  Gotcha
Yes most do but unfortunately some do not it seems

----------


## Moondog55

So this is my final solution.
I went to Jaycar and got a small tube of heatsink compound, cut the clearance nipples from the base of the plastic housing and used some zip ties to mount it to an old Pentium heat sink.
Since I did this the temperature of the Switchmode PS casing has dropped considerably, passive airflow over the heatsink is good as it's no longer sitting on the desk top, I simply raised it with a longer AC cable and now it fits above the tower

----------

