C0 Lathe Blowing Fuses. Control board short?

All starting to sound a bit too complicated for my basic electronics knowledge. 🙃

I had to look up what an SCR is. 😊 Basically a diode/switch thing that needs to be powered to open? No idea how U would test such a thing?

The most likely failure mode for SCRs is anode to cathode short circuit. Looking at at the devices the way they are mounted on the heat sink and with the pins facing down the centre pin is normally the anode and the left hand pin is the cathode. This is the layout for most SCRs in TO200 packages. It would be a good idea to confirm this by looking for the datasheet for the devices used on your board. you can normally find the datasheet using Google or other search engines. Just do a resistance test between anode and cathode with both polarities. Both readings should show over range on your meter. (Or at least a very high resistance.) If they are short circuit you will get a reading of almost zero ohms in both directions.

Les.

Tested the SCR things and they where fine. The diodes arrived today and I fitted them this afternoon. Everything is now working again. So I am a very happy bunny, and I saved a hundred quid! 😁😁👍

Just thought I would post the conclusion for future reference. Thanks for the help everyone! 👍

Glad that you are up and running again.

Thanks for keeping us updated with a happy ending. Nice to know the outcome when someone has a problem.

Howard

It poses the question, Why did the diode(s) die ?

Believe me, diodes die !

Hi, It might be worth fitting a fuse in one of the motor leads,then if the motor stalls ,it will hopefully blow the fuse before damaging the controller .

Maurice

No point in fitting a fuse, semiconductors blow faster than any normal fuse.

Diodes, like most semconductors fail for a number of reasons including manufacturing defects, but most common is overloads, including voltage spikes. Given it's a low cost lathe, it was probably marginal manufacture.

Robert G8RPI.

Moral of the story - always ask for help!

On a personal note, im really glad I "had a go" at fixing this myself. I've learnt a few things and I actually really enjoyed the process. 👍

Thanks for the update.

I'm really pleased you fixed it, I was holding my breath.

Bear..