That is the reason for “open/short” 
Although I am surprised it does not blow a fuse with a short 
https://www.digikey.com/schemeit/project/k40-lps-2-EFKO7C8303M0
That is the one that paul is suggesting.
Can you see under the pCB any burns?
The diode is showing open, no continuity.
Did you check it both ways with the meter? i.e reverse the leads?
I thought I had, but I doubled check and I actually get 2Mohm the with the leads reversed.
short one way and open the other? Seems ok… There is one more of the same diode in the LV supply. That other diode to the right looks like a different part???
That’s an old vintage supply.
In any case, I doubt you can find a replacement diode by Monday when your new supply comes?
May be good for parts?
Do you know that the old one only has a bad HVT???
You could swap the new HVT with the old one.
If they have the same HVT.
The challenge with these supplies is that when the HV driver side goes it usually takes lots of components with it that is why I stopped repairing them.
Pull the PCB off the frame (on the most recent one) and see if there are any burned parts on the other side. Those FETs are the drivers.
Yes I have replaced them with FR302’s to fix it from JayCar since I could not want to order them online and wait for weeks to receive it. I believe originally they were MUR302…I can’t remember. Also Replaced the MOSFETs and in another PSU the HT coil. So anything can got wrong without the fuse blowing. It is not a great design and I toyed with the idea to design a better one but you cannot compete on price. The HT coil is already $46 so that leave no margin for PCB, case, shipping and a bit of profit.
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Nothing obvious.
Are the two hvt’s the same?
No markings on the HVT for the newer supply. The way they connect are very different.
HVT coils can be bought from Aliexpress (CloudRay). They aren’t cheap and you have to wait weeks to receive them. The one I got had screw terminals instead of wire leads. However it did work fine after a small ‘Paul’ semi prof mod with hotglue-ing the HVT coil in the case…(not proud about it)
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Since I’d seen a post by the original designer of the k40 where he stated the LPS was supposed to be a reference design, not final design, so he provided the 24V output with only 1A( or was it 2A?) so no headroom for 2 stepper motors. Once I read that one of the first mods I did was to get a 24V 5A PS and remove the 24V load on the LPS. Eliminates excess heating in the LPS case and provides more power for the stepper motors when needed.
Were you using the 24V from the LPS when this failed or do you have an offboard 24V power supply? It could be 100% unrelated to the failure, just keeping an eye on if there’s really any value in removing the 24V loading. Thanks.
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I had run the machine earlier in the day with no problems. Then later I went to turn it on again and nothing happened. No sounds or magic smoke.
I don’t have a sep 24v supply but I will be getting one.
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Pictures of the two different HVT’s?
The HVT’s have various mounting options.
The cost of the HVT’s + the challenge of finding what parts were bad is why I stopped recommending repairing. By the time I found and replaced all the bad parts, I had more in the repair than the $ of a new one.
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