SHM0609 Need new transformer

[charnwooduk]

My machine had some very strange and loud noises from the control box today, complete with some sparks and a smell of burning electronics. I immediately switched off the machine and took off the access panel to take a look.

I suspect the issue is with the transformer at the front left of the control box, as there is some scorching around the input terminals and this area also smells.

There appear to be two transformers that I think are powering the 3 yako stepper motor drivers. The rear transformer appears larger and i suspect this is because it is powering two of the yako units and the front transformer was powering only one.

I need to get a replacement ASAP, but have no idea what power rating I need. I'm in the uk , so need 240>50V step down but have no clue as to the VA rating i need.

The yako units appear to be set to supply 3.8 amps to the stepper motors.

Can anyone offer any advice about what VA rating i should get? Thanks

[Al_The_Man]

Is it the transformer or just a bad connection causing the overheating?
The VA will be the voltage x the max current the transformer will draw, it can be calculated using either primary or secondary voltage x current.
Al.

[charnwooduk]

Is it the transformer or just a bad connection causing the overheating?
The VA will be the voltage x the max current the transformer will draw, it can be calculated using either primary or secondary voltage x current.
Al.

The connections seemed ok, although I am going to double check the earthing of the machine, as I know others have seen issues there.

So (I am guessing) 50Vx3.8A = 190VA Which means I should go for a 200VA supply?

I have a local supplier who has a 2 x 24V transformer rated at 200VA, I will see if it is possible to series the output to give me 48V.

[jalessi]

I believe you have a bad connection at the transformer terminal, either a screw is loose, you have a bad crimp or the solder connection is cold.

http://www.degson.com/en/showproducts.asp?id=311

Jeff...

[jalessi]

Wiggle the wires back and forth and look for sparks.

[charnwooduk]

I took the transformer out of the machine for bench testing. Wired the input to the mains and put a multimeter to measure the voltage across the output terminals.

Turning on the mains and the transformer buzzed, and smoke came from behind the input terminals. I think it is fair to assume the transformer is dead !

I am pleased that this is the issue, as it is the cheapest part of the machine to replace.

I checked the earthing of the machine and sure enough there is no connection the earth terminal of the power socket at the back of the machine.. so even though all the components in the control box are correctly earthed to the chassis, there is still potential for some nasty shock!