Mirka Power supply - need electronics expert!

[grim_d]

Evening all,

I have a Mirka Ceros electric orbital sander which is truly brilliant but the Chinese power supply gave up the ghost tonight, the power supply (22v 9A) is cutting out immediately on anything other than lowest, even then it's a struggle to get it going as it thinks it is detecting too much load. Running the sander on lowest and you can watch the power led fade out and eventually give up, testing with a meter confirms that the voltage is dropping off.

Having rigged the sander up to a 12v server supply I am back in business albeit at about half speed.

The real problem here is that a new power supply is about £200+ I can almost guarantee it is a stupid 5 pence surface mount component has burnt out and is causing the issue but unfortunately I do not have the know how or equipment to identify said component.

I've had my electronics (hobby) man take a quick peek and nothing stands out at him, again he lacks the testing equipment. Only thing he mentioned was that one of the thyristors looked like it may have got warm but not overly so.

Some pictures of the supply, nothing looks burnt or too shady, suggestions on where/who to go to from here?

 

[bump]

Where abouts are you based?

 

[grim_d]

Ayrshire - Scotland

 

[Cobs]

Mine went after just 2 days, apparently a common problem with the power supplies so may be worth contacting vendor even if out of warranty - new one has been fine.

 

[grim_d]

Technically it's second hand so no idea on the vendor, must be a good 4 years out of warranty now too! I'll try contacting mirka or a mirka repairer too.

Not in their interest to tell me whats wrong with it though.

 

[carbon]

I would check the capacitors first but you need a tester for that as I think that's a common failure on switch mode power supplies. They usually bulge if they have failed but not always.

 

[xmetal]

I would check the capacitors first but you need a tester for that as I think that's a common failure on switch mode power supplies. They usually bulge if they have failed but not always.

You beat me to it.

Some makes of Chinese electrolytic capacitors are renowned for failing. If you have to change them, go for a good make such as Panasonic or Rubycon. You probably want the low ESR type designed for switch mode power supplies and get the 105° version.

 

[grim_d]

Ok guys I will investigate testing the caps and report back.

 

[carbon]

Does this unit have a fan for cooling. I got donated a dvr as it didn't work, found that one of the power supply fans wasn't connected and a few of the capacitors had failed as a result. They really need to be checked for esr value as well as capacitance.

 

[MattF]

Ok guys I will investigate testing the caps and report back.

Don't bother checking them. Just replace them all. The reservoir cap should be fine, but replace the sub 50V caps.