Castomig 250c Welder - Control Board

[Mad Professor]

Hi All.

I am trying to fault find and repair a control board for a Castolin Eutectic Castomig 250c Welder.

The issue with the welder was that as soon as you unit was powered on, the spool feed would run at max speed.
It would not matter what the speed feed was set to on the front panel.

I have so far traced the fault to the main control board. in particular a BUZ10 Power Mosfet.
All of the pics were showing as a dead short. after removing the BUZ10 from the PCB my DMM reads dead short across all three pins.

Here is a link for the BUZ10 datasheet <Click for datasheet

I normally order parts from RS Components UK, but it seems that the BUZ10 is not something they stock.

Could someone please help me found a compatible replacement for the BUZ10?

I am also concerned that maybe the driver circuitry for BUZ10 has been damaged.

Thanks for your time.

Best Regards.

[singapol]

BUZ10 is obsolete. The nearest equivalent is IRFZ34 which is available from Element14 UK. Just key in IRFZ34
to search, there are a few choices and price. PS it's listed in RS Electronics too.

IRFZ34 datasheet-- Compare carefully with BUZ10.
http://www.vishay.com/docs/91290/91290.pdf

[Mad Professor]

singapol: Thank you for your reply, and your suggestion to use the IRFZ34, as a compatible replacement for the BUZ10.
I will have a good read of both datasheets and compare, before ordering any new parts.

What would normally cause a Power MOSFET to go dead short across all three pins.

Thanks again for your time.

[tautech]

What would normally cause a Power MOSFET to go dead short across all three pins.

The back EMF from an inductive load.
The inbuilt free wheeling diode can often manage the back EMF but it's poor design to not add a snubber to specifically manage back EMF.