Switching Power Supply not deliwering full power like it used to.

[Pexy13]

Greetings!

I have a lava lamp that worked fine but I noticet recently that when I power it on it's not as bright and warm enough to get the wax floating.
I measured the output of a 12V 2.5A PSU and it's 12.1V when no load is connected but when I load the output whit the 12V 20W  bulb the output drops to 1.8V and is sloooowly climbing up at around 0.01V per second. I don't know if that's because of the bulb heating up or something regarding the power supply.
I tried powering the lamp with a different power supply (12V 1A) for a few seconds and it's a lot brighter then with the old psu.

Does anyone have any ideas what might be wrong? I used the lamp whit this power supply for around 3 years and it has a good amount of hours on it. Is there something I can replace or ddo to fix this problem? Any advice is welcome.

Cheers!

[wasedadoc]

Probably the most common problem with switch mode power supplies is deterioration of the electrolytic capacitor(s) on the output of the low voltage rectifier.

[wraper]

I suspect bad electrolytic capacitor with such failure. They are not nearly as often faulty as some people tend to blame them for everything, but this is one of those cases where electrolytic cap is the primary suspect.

[Pexy13]

Is it worth opening the PSU and replacing the capacitors?

[NiHaoMike]

If it's just a 12V halogen lamp, replace the PSU with an "electronic halogen transformer", which doesn't filter the output so less to go wrong.

[wasedadoc]

Is it worth opening the PSU and replacing the capacitors?

Does it open up readily or is it a glued /welded case?  Problem with the latter type is getting it apart such that it can be closed again and remain safe.

[Pexy13]

If it's just a 12V halogen lamp, replace the PSU with an "electronic halogen transformer", which doesn't filter the output so less to go wrong.

So I could just power it with a 12V hahlogen transformer connected directly?

[Pexy13]

Is it worth opening the PSU and replacing the capacitors?

Does it open up readily or is it a glued /welded case?  Problem with the latter type is getting it apart such that it can be closed again and remain safe.

It is glued shut but i oppened psu like this before with a hacksaw and later glued em back up and wraped them with electric tape so I think they are safe again. And the only one using the lamp is me so there's no danger for anyone else getting shocked.

[tunk]

It is glued shut but i oppened psu like this before with a hacksaw and later glued em back up and wraped them with electric tape so I think they are safe again.

You could also try with a vice or polygrip pliers and see
if you can crack the glue/welds. If you open it, post photos
of both sides of the PCB.

[Pexy13]

You could also try with a vice or polygrip pliers and see
if you can crack the glue/welds. If you open it, post photos
of both sides of the PCB.
[/quote]
I also used a bench vice to crack a few of them open. I'll post photos over the weekend when I get to the home shop. Cheers!

[wraper]

Those are too destructive ways to crack it apart. There are different ways to open nicely. You can put in it a freezer, then take out and quickly (like within 30 seconds) hit with a rubber mallet all around the weld. Freezing temperatures make the weld fragile. Be sure to put it on some hard surface, holding in hand while doing so will likely result in a broken inductor or transformer. Also there is a chemical way. Special solvent mixtures do exist but gasoline, nitro solvents and acetone work too AFAIK, not as well though. And may leave marks on plastic. Usually solvent is applied across the weld, left for around 5-10 minutes and cracked apart with a little bit of force.

[wraper]

[Pexy13]

if you can crack the glue/welds. If you open it, post photos
of both sides of the PCB.
[/quote]
I opened it. Here are a few photos. I can see the output caps bulged at the top so they are probably gone. If I change them it should work like it used to?

[wasedadoc]

Use good quality, low ESR, 105 degrees caps.  I prefer Panasonic ones.

[wraper]

For better reliability you can add a 4th cap which is not assembled.