Rebuilding the K40 - flat cable needed

Price from Cloudray $US136, Price from Light Object $US185.
Both prices include shipping.
If I buy from Cloudray, I can get a power supply for $US43, free shipping.

I’ll wait for some more answers/suggestions over night before ordering.

I forgot you are in AU. I bought my 100W tube from LO in part to work with someone in the US if I needed help, which wouldn’t help you any. (You might Display your national flag with your user name to help me out here. :wink: )

I have ordered a few times from Cloudray and except for “free shipping” for a small part that came by the small packet service and took about a month, shipping was fast. I would order from them again.


Found a flag :grinning:

Delivery from Cloudray is quoted as May 1st. That should give me time to finish off everything else.

I can only work on the laser once a week for at most a couple of hours. It’s 60 km away from home.


:australia: :tada:

And to think that I complained that my makerspace (which closed shortly after I joined, just my luck, or am I the curse?) was approximately half that distance!


Well an order has been placed for the following:

Not sure I’ll need this last item but after the bodge that was used to install the last tube, I’d rather have it and not need it. Total cost $A286


That last item seems to show only 1/2 the cable and connector?
Those connectors have two parts Cloudray Laser Power Supply High Electricity Adapter / Connector for High Voltage Cable|adapter connector|connector adapterconnector power - AliExpress


Thanks Don I think you’re right. The tube does seem to have a wire attached as supplied but couldn’t see how it was terminated. I’ll order this bit too ‘just in case’

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… also in case you do not know, Just twist the wire around the anode and silicon it in.
Do not solder or crimp …


Part of the reason that the current tube broke was that the anode had been soldered (at least I tell myself that so I don’t feel so bad…).
I’d guessed from looking at the high tension connector I’m buying that it was a mechanical connections i.e. alligator clip, or similar.
The lead from the LPS is just long enough to reach the anode so I’ll have to splice it into the new lead. I seem to recall reading (probably from your blog) that the HT lead is part of the fly-back transformer and not separately replaceable. Other than making sure the splice is as far away from any metal parts and is insulated correctly (RTV silicon should do it), any other things I should be aware of?

Instructions on how to splice the HV cable safely are in @donkjr 's blog, linked from this #k40:intro article:

Here’s a search for more discussion on this forum:


I’ve been over the stuff in @donkjr’s blog and looked at all the videos he’s linked on the subject of tube change. Splicing the wire is not a problem but my main concern was the best/correct way to attach the wire to the anode. The Cloudray tube does come with a wire attached (not sure on the method - mechanical or soldered) so all I should need to do is to choose the best location for the splice.

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Is it 7 or 8 mm that fits on a “standard” k40 laser tube?
Regards Bernd

CLoudray told me 7mm was fine. Hope they’re right.

Thanks for the response :smiley:

Sorry for the delay in responding:

I would place the HV connector where the point of splice needs to be. Essentially the connector is in place of the spice. I like to attach 1/2 a high voltage connector to the HVT’s wire and then the other side of the connector to the anode wire. That way when I replace either the tube or the HVT I just remove and replace 1/2 the HV connector, no splices.

In the case where you have a preassembled HV connector & wire a splice will be necessary. RTV will work, make sure it is the high dielectric type.

Use “ball soldering” on any solder joints to prevent corona. Keep in mind that the voltage can jump 1-2" if uninsulated. It also can find uninsulated tracks through gaps in connectors to ground.

The anode pin is made of hardened metal (Inconel?). You actually cannot solder to it. If you try you can crack the tube. Those that do actually create a cold joint that mechanically attaches the wire to the pin, no better than twisting it on. Unlike normal circuits 20,000v does not need a gas tight connection. Wrapping the wire on the pin before potting it in silicon is sufficient. Wrapping followed by a tube filled with silicon is the traditional method.


Not much I’ve been able to do on the K40 this week as I’m waiting for parts. Most of the AC wiring has been done with the exception of the two SSR’s that will control air assist and exhaust fans.

I’ve been spending my spare time creating wiring diagrams, largely based on those provided by @donkjr . I’m trying to document all the wiring colours used previously with the new stuff I’m putting in - just in case I get hit by a bus and someone else has to pick up the job. :grinning:
I’ve been using kicad for this. No PCB’s needed so just using the schematic editor.

I’ve also been working on a new control panel layout - first draft. Not sure if there is going to be a Z axis platform but ‘just in case’ . The ‘display’ will be a 3.2" il9341 based, touch screen unit probably driven by either an Arduino nano or perhaps an ESP32.