Electronics > Repair

Can someone identify this component/help me repair this laser power supply.

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It might be possible to patch in something like a TOP225YN.

Too high or too low frequency might work not quite right, or it could smoke again.

To get the frequency, it might be possible to estimate it from the core volume.  We need to know more.
I am guessing it is a flyback convertor.

Can you find out how much power it is supposed to supply?
The transformer core material?
Core dimensions?
The values if the snubber circuit components? (an R in parallel with a C,  then in series with a diode;  that circuit is in parallel with the primary of the transformer; the diode points toward the + of the main capacitor;  if the snubber is not that topology, then state what it is.)

The more info the better.

Hey, I'd just like to say thanks for all your help so far :) I don't have my multimeter on me right now, I'll confirm tomorrow about the values. Here's some more information

The core has EI28 stamped on it, there is a EI28 series of transformers https://www.sumida.com/products/pdf/EI-28.pdf which are good to 300kHz apparently?

The low side of the transformer feeds into two schottky diodes in a -VE-0-VE+ configuration.  http://www.datasheetcatalog.com/datasheets_pdf/S/T/P/S/STPS2045CT.shtml

the only other interesting components on the low side are a lm324n op amp and some power transistors


You're welcome.  I've been in your shoes and I know how it feels.

EI-28 is the core size.  That is good to know.  The operating frequency is going to depend on, among other things, the core material.  The sumida does not state what the material is.  Even then, just because a material is rated to 300 kHz, does not necessarily mean that they chose to run it there.

The next most important thing is the total load power.  Is the 250 mW the beam power or the total power?  The TEC is probably going to suck down a lot.

Is there any shim or gap visible between the E part of the core and the I part?

The others in this thread should feel free to jump in too, but I guess they went to bed.

If you have access to an x-ray machine, it would make it easier to see the gap if it is in the center leg.

The secondary side stuff isn't too useful unless it gives some clue about the voltage and current output.  Really what we're after is the power the transformer needs to pass.

What you said "The low side of the transformer feeds into two schottky diodes in a -VE-0-VE+ configuration." I'm not too clear on.  Can you clarify?  I am starting to think this is much more than 50 W and that it might therefore be a forward converter.  Can you identify any ratings or values on the secondary side inductors?

There are some other parts it could be, that while still obsolete, seem to be more available.
And here are some app notes on power supply design using the parts:

It could still be a flyback with that diode configuration.  It just threw me off for a moment.

More stuff on DPSS laser repair:

Hey sorry I went to bed. What I meant was that the secondary side has a split rail configuration, I assume to generate a negative voltage to power the op amp. I can't see a shim in the transformer core, looks like it's all ferrite.

I don't think the power consumption is would be that great. 250mw of green light would need about 2w of pump diode for the laser cavity. So maybe 5w total electrical input for the laser. and another 10w or so for the TEC to cool everything? The traces on the low voltage side look like they've been designed with high current in mind though.

I couldn't find my model for sale any more, but the power supply 'box' of this laser http://www.ebay.com/itm/DPSS-100mW-130mw-532nm-Green-Laser-Diode-Module-TTL-Analog-110VAC-220VAC-Stage-/120964892851?pt=US_DJ_Lighting_Single_Units&hash=item1c2a11c8b3 looks VERY similar to mine.

What's interesting that that they state 5v at 1a for 100mw of laser output, so for 250mw that would be 10-15w maybe? I think that seems about right?

Edit: I took a look at the application notes, the primary configuration looks very much like that!

the values for Rsn and Csn look to be 5.6k and 1uf

Also now that I think about the laser power supply has a 0-5v TTL input to enable/disable the beam so it would make sense if the board was running at -5v,0,5v

Based on this being ~20W supply, my wild guess is that it is supposed to run at 50 kHz.  To be on the safe side, use the 800V part (KA5L0380RTU) as opposed to the 650V.  Maybe try it with a 100W light bulb in series with the line input to start testing.  Use AN-4141 for troubleshooting, especially the section on subharmonic oscillation.  If its doing that, the frequency may be too low.  Check the temperature of the transformer and U1 for overheating.

Edit: I will add that there might be a current regulator in the laser, so that the external supply needs to supply more power to accommodate that.  The modulation goes to the laser module and not to the power supply in question, right?  It might get routed through the power supply without connecting to any of the power supply circuitry.  I'll still stick with my original answer though.


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