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How to test the 40w co2 psu without the tube on

Joined
Dec 13, 2016
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Hello guys. Recently I bought a k40 laser machine. After fitting all the accessories I pushed the on button and blew off the fuse. I checked the tube and it was full of water. I guess it was cracked so i asked for replacement. The seller told me to disconnect and take out the tube,replace the 6A fuse and turn on the machine to check if the psu is ok. I did it and again the fuse blew off. My machine doesnt have a on/off laser button just a central switch. On the psu i see that they have soldered together those two pins for the laser switch. My thoughts are that i cant turn on the machine without the laser connected and the only way is to free those 2 pins(cut Voltage to anode) so i have power only to the motors. All the other wires look ok (attached).I just dont know if it those 2 red wires going to the psu in AC AC need to be checkedfor polarity issues.Any ideas on this?
Thank you in advance

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Joined
Sep 12, 2007
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I'd be inclined to agree that disabling the enable switch would disable the laser... if that is indeed what the switch/pads are labeled. You are correct that running the laser output without a laser will likely damage something. What are the green wires' connector labeled as?
 
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Dec 13, 2016
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Searching the web i've seen that those 2 soldered pins are the interlock of the laser or on/off switch and since there is no extra switch on the panel it means that when i turn on the central switch, laser is on as well.
so as you see on the attached photos from left to right we have:
L- : cathode from laser tube
FG: Floating ground goes to chassis ground
AC: + wire comes from AC plug
AC: neutral wire comes from AC plug
PG: laser interlock and ground (soldered)
K+K- : laser test. Wires goes to control panel
G IN 5V: power adjustment. Wires goes to control panel
24V G 5V L: Wires go to M2 Nano mainboard for the motors etc

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Joined
Sep 12, 2007
Messages
9,399
Points
113
My best guess would be desolder the blob, and apply AC with nothing else connected. Then measure the output voltage rails 5V and 24V as the seller suggested.

Using an ohmmeter with everything off, you can also measure from rail to ground, and each load to load's ground to check for shorts which may be causing the overload.
 
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Dec 13, 2016
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thank you very much for your ideas. Everything worked great and i have connected a laser on/off switch to the interlock pins.
 




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