fried

[corrie]

Hello all ,well today was not a good day. I was 90% through a rouching pass when I noticed that all my axes stoped running and then seconds later my shop filled up with smoke. After quickly turning everything off and pulling out power cables to see what was the matter ,it seems all that smoke came from my power supply. Here are some pics, I,m stumped as to why this happened.

[gary_calfee]

That kind of thing can be complicated to figure out and it is hard to tell the wiring configuration from your pics, but sometimes the most obvious explanation is correct. It looks like there was some arcing to the torroid transformer hold down bolt out near the end. From the picture the wires look very close to the threads; were they in contact with the bolt? The transformer will generally vibrate (hum) as it operates, could it have rubbed through the insulation during operation? The bolt should be at the cabinet or earth ground potential and would provide a very solid ground path. The question is did the arcing cause the problem, or happen after the insulation was compromised due to the short. Of course, all of this is speculation from just looking at the pictures. Hopefully the rest of your electronics were spared....

Do you have a fuse on the primary side of the transformer? Clearly those wires were carrying a lot of current.

Good luck with your repairs!
Gary

[vtxstar]

Identify which lines melted - AC input or DC output of the bridge.

If the AC, suspect the bridge rectifier.

If the DC, suspect anything on that side, but most likely a power driver section.

I think it is time to evaluate your fuse (or lack of). It should have blown before the insulation melted.

[corrie]

Thanks for the reply, unfortunately I,m completely daft when it comes to electronics . The power supply was built for me , I guese it,s time to learn.Yes a fuse would have helped. I,ll be taking it in to get fixed and see what started this mess. I,ll follow up later. thanks.

[Al_The_Man]

It appears to me the secondary conductors to the bridge took the brunt, this might indicate the bridge shorted out, if the primary side was fused right, the short should have reflected back from sec. to pri. and blown the fuse.
Check the bridge for short circuit between connection posts after disconnecting.
Al.

[neilw20]

The steel case would not make a good heatsink for disipating 10-15w
It looks like the rectifier has shorted and may have damaged the transformer.
Bit hard to tell friom the fuzzy pictures.
Wrong sort of fuse wire in this application. (constructive comment).
I bet the builder didn't supply you with a circuit either.
Put a 2 amp fuse in series with the mains supply.
Disconnect the two burnt wires and remove them entirely.
Turn it on.
Leave it on a minute or so.
If the fuse survives and nothing smokes, then replace the rectifier, and give it a better heatsink.
If the fuse blows, it looks like the transformer is fried also.

[corrie]

Thanks to all who have replied , It seems the rectofier had come loose from the casing and over heated .my buddy checked the transformer and it seems ok. It will be rewired with an in line fuse this time and all wires will be better placed.When I get it back I,ll post some pics and a lot clearer this time. Like I said I don,t know much at all about the elctronics end of things but I,m going to learn.Are there any good tutorials of a complete power supply explained in layman turms: ie:where the signal path starts ends,what the seperate components are and do , things like that. Thanks very much to all, Corrie.

[keebler303]

http://www.antonine-education.co.uk/..._3/TOPIC_3.HTM

http://www.antonine-education.co.uk/..._smoothing.htm

Make sure to put that rectifier on a heatsink this time!

Matt

[neilw20]

Originally Posted by keebler303 http://www.antonine-education.co.uk/..._3/TOPIC_3.HTM http://www.antonine-education.co.uk/..._smoothing.htm Make sure to put that rectifier on a heatsink this time! Matt

WITH HEATSINK COMPOUND. AIR GAPS INSULATE HEAT

[Al_The_Man]

I don't see a hot rectifier causing that damage, it has the appearance of excess current, have you checked the bridge for short circuit yet?
Al.

[neilw20]

Spot on Al_TheMan.
Because the input wires to the bridge rectifier melted and the outpuut ones survived, the BRIDGE MUST BE SHORTED!

Save yourself a fuse.

[corrie]

Ok so the bridge rectofier was the problem. Everything else seemed to be fine.Wires replaced and new rectofier instaled also a fuse. Hooked it all back up and joged the machine around and all was fine. Loaded a previous program that I was trying to finish before this all happened and all axes stopped working.Turned the power supply off and found that the fuse had blown. Specs on my transformer are 300 volt amps/ two paralell outputs/ 115 volts on the primary and 20 volts on the secondary. My motors are 4.6 amps .The fuse that blew is a 5 amp. The transformer tested ok for continuity but was not tested under load. i havent yet but if i put in a 10 amp fuse and it runs does that mean all is well and if a 10 amp fuse blows then the transformer is more than likely toast?