Bad Tube or PSU?

Discussions on optics for laser cutter/engravers

Re: Bad Tube or PSU?

Postby dandumit » Sat Mar 23, 2013 5:46 am

Hi,
Could you please tell us what's inside of the left vertical black box ?

BR
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Re: Bad Tube or PSU?

Postby TLHarrell » Mon Mar 25, 2013 4:46 pm

That black box looks to me to be some sort of PWM adjustment. Note the trim pots (or caps). It's all potted in epoxy or something. Some sort of daughtercard setup.
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Re: Bad Tube or PSU?

Postby Fred » Tue Mar 26, 2013 11:04 am

Considering how expensive PSUs are and the fact that it may well be a cheap component that's gone, has anyone actually taken a general look into PSU repair?
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Re: Bad Tube or PSU?

Postby bdring » Tue Mar 26, 2013 1:07 pm

The failure is typically in the high voltage insulation of the transformer. It is not something that is repairable. You may find collateral damage, but that might re-fail again with transformer. That is a very dangerous item that can store a charge. Be very careful.
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Re: Bad Tube or PSU?

Postby Fred » Tue Mar 26, 2013 4:41 pm

Ah - fair enough. Not just replacing a dud electrolytic capacitor then.
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Re: Bad Tube or PSU?

Postby Techgraphix » Tue Mar 26, 2013 10:34 pm

Even if you could find this particular HV-transformer, it is probably more expensive than a complete new supply.
There is a way to test a HV-transformer for shortings: with a scope and a squarewave oscillator you will see reflections of a shorted winding. Or when you use a capacitor ad look behind the capacitor with your scope you must see some oscillations. If there are no oscilations at all or just one or so, then there is a short in the transformer (probably secundairy)
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Re: Bad Tube or PSU?

Postby timogiles » Wed Mar 27, 2013 4:24 pm

dandumit wrote:Could you please tell us what's inside of the left vertical black box ?


I'm not 100% sure what is in there. I think TLHarrell is probably right. It is fully potted, so you have no shot at seeing what it is or servicing it.

Fred wrote:Considering how expensive PSUs are and the fact that it may well be a cheap component that's gone, has anyone actually taken a general look into PSU repair?


I agree with Bart. I'm 90% sure that it was the flyback transformer that broke. I googled the model number of the flyback but i didn't get any hits.



My replacement supply came yesterday. upgraded from a 40W to a 60W supply, I'd like to move up to a 60W tube someday. The 60W supply is physically larger than the 40W supply. Peaking in the vent holes I can see that it actually has 2 flyback transformers. I'll post some pictures of the size comparison tonight when I get home. The size difference isn't a problem for me, I had plenty of room to fit it. I ordered the replacement on ebay from love-happyshopping. $188 with free shipping from their California warehouse.

Edit: I forgot to mention, everything is working with the new PSU. :D
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