Ful Spectrum 40W laser PSU probs

[Mosaic]

Hi all:
My laser beam just quit firing tonite. Even pressing the test fire button on the PSU does not fire it. All other functions and PC interface seems fine. No boot errors or probs with gantry control.

Seems it might be the HV section.

Can't find ANY resources/schematics/guides/blogs to T'shoot this thing. 40W CO2 laser PSUs are fairly common, but doesn't anybody fix one?

 

[Tony Stewart]

https://www.ebay.com/itm/like/16155...7290-0%26rvr_id%3D1063852062520&ul_noapp=true​

 

[Mosaic]

Looks nothing like the item I have...there are a couple that look similar on EBAY.
Can i ask for advice on testing the PSU out of the laser such as how to load the flyback HV side and do the testing?

 

[Tony Stewart]

• I've never tried a CO2 laser, but sure. Basically works like any gas tube with HV trigger and LV when conducting, except light emission resonates with wavelength, gas type and gap.
• No idea what HV and LV are, but 1st guess is 50kV and 10kV
• 
  
• Ensure cooling works,
• check HV uses rubber insulated wire. Beware of dust and creepage arcs.
• Clean well and add silicone coating helps for exposed HV conductors ( I used to do this to fix old triplers)
• Limit current to 10 mA for long life

mirror alignment is critical

 

[Mosaic]

Need to figure some kind of high wattage insulated resistive load to test the flyback HV side. Perhaps 2 to 3 Megs.
I can measure current with an ammeter on the low side of the HV going to ground, I have a 200mA unit around (analog)

 

[Mosaic]

Well, I stripped down the PSU and the Flyback is a basic transformer with the secondary grounded and one primary, no extra primaries for oscillation feedback.
Secondary is open @ 20MΩ. Took it out of circuit and tried for a 2mm spark using a DC supply to 24V and tapping the primary ( 0.25 Ω DC, 1.4Ω impedance @ 1Khz) on/off manually with a heavy wire feed. Got no sparking at all.
Two IRFP450LCs drive the primary. They seem ok but look like refurbished 'pulls'. Some rework was done before on these FETs, solder balls around & flux.

Ordered a replacement flyback and replacement FETs as well.

This seems like a good way to load test a running HV system.
**broken link removed**

 

[Tony Stewart]

• it didn't mention gas generation of H2. & O2 and sulpher compounds, etc

It's the insulating ion flowing contaminants that detonate causing H2O to separate, usually at the electrodes or any barrier I believe.

 

[Mosaic]

Ok got a replacement flyback and did some basic 12VDC tapping the primary tests on it ...getting a spark on the secondary.
Installed it in the PSU and the test button initiates spark as well, so HV looks good.

Good 5V and 24V supplies for the motors. Might be able to squeeze in a small fan b4 reassembly to help flyback cooling.