Lasever Power Supply ground issue

[CDBEAM]

Recently I have had my projector disassembled to replace a failed Scanner amp board. I took this opportunity to chase down a ground fault potential, measured at 4.2 VDC I had between where the lasers heads and drivers are mounted and the level where the power supplies are located. I should note that I have a three (3) level design…each level being an Aluminum plate.
The leakage is sourced from BOTH Lasever Green and Lasever Blue power supply. See the attached pics. My bet is that the insulation between the power Mosfet and PS Aluminum case is split. The Mosfet and case are now in contact…causing the problem ( Buffo also sez this is likely).
My fix was to electrically isolate the PS mounting plate from the Aluminum bottom level plate. I used 8-32 Nylon bolts and 1” Nylon washers to secure both Power Supplies. This is one way to do it. I suppose you could redo the Mosfet insulation….but I went for a quick and sure fix. If you have any Lasever Power Supplies…you may have a ground issue. See pics of the Green PS interior and the bolt/washer combo’s securing the Blue Laser PS.
CDBEAM

[hobbybob]

My experience with Lasever Powersupplies is that they run extremely hot.
Will that small plate be sufficient to cool them ?

[sbk]

Interesting, I had a few days ago a 100mW 532nm Lasever which had a ground fault, but it was in the head, not on the driver... The anode of the LD was connected to the laser head case! I noticed it only when I installed the laser into the projector. Then I had the full 7A of the power supply throwing though the small modulation cables to the projector's ground, they was going hot But the laser was still working correctly with this fault, a chance I noticed it

And yes the driver goes hot, but now they put a fan on both driver and head, which seems enough to keep temp low even without base plate.

[CDBEAM]

My Lasever green Laser head @ 350mw gets hot....but the Power supply stays slightly above room temp.
The LH has both Fan and TE cooling added to the underside of my top plate...see pic. No issues with LH temp....after all that....there should NOT be any temp issues.
But yes....now there is an air gap between PS and base plate...but I do not think that will be a problem??
We will see ??? I wonder how thermally conductive is Mica ??

[buffo]

My lasever units run fairly cool, but they're lower power (150 mw of the green and 100 on the blue) so that may be why.

I agree that it's a good idea to have some airflow across the driver modules though. But the heads tend to get pretty warm too...

Adam

[Steve Milani]

I apoligize for my out topic....
Hey Adam.....
Old torpedo....I've seen right? The numeber of your post! More than two billions????



Join Date Jan 2006
Location Charleston, SC
Posts2,147,483,730

[buffo]

heh! Our admin was having some fun at my expense. Shortly after he updated the forum to the new version, he changed my post count to be equal to the maximum number possible for a 32-bit signed integer, which is 2,147,483,647. And then, just a few hours later, he changed Diachi's post count to be one greater than that number. (Which obviously means that the post count isn't stored as a 32 bit signed integer!)

This was almost a month ago, and both of us have posted lots of messages since then, so the joke doesn't make much sense now... But if you want to read the original thread where it all happened, here's the link.

Adam

[daction]

kai ora , I too have had a problem like this (laser world 300 mw).I opened up the power supply to find a piece of plastic sheet isolating the back of the pcb and the case. There where also some spacers that gave about a 3mm gap between the pcb and the case. I increased the gap , sealed the edge of the plastic sheet with tape . I then made a nice earthing system . I then measured the earth leakage(with a pat tester) with the signal wires not connected it measured .44 ma . when i pluged in the signal wire , the pat tester beeped and the earth leakage increased to 55 ma . In new zealand the maximum earth leakage is 3.5 ma so well legal . one transistor is quite hot but working fine . I put 50 volts between the 240 volt side and earth 55 mega ohms resistance ( mint). 9 volts to all the other connections they where all good too . The power supply runs hotter than it used to but its working . going to look at the dmx board next . When my laser arrived from china it had no earth system . peak temp was 37(on a hot day) Head is cool . To be honest not that happy the power supply used to run cool .

[daction]

hey just isolated the base of my power supply. operating temp has dropped by 8 degrees. hope it doent become live with mains voltage( It wont blow the fuse). How else can we fix problems like this ?

[shrad]

I'd have placed an oil-impregnated paper foil between the head and the baseplate

it appears to me as a better choice to have the PSU grounded properly in the case of a switcher failure (likely to happen one day or another if the PSUs are chinese or purposedly underspec'ed by the manufacturer like most of the budget switching power supplies)