Transformer gets too hot to tocuch 80oC [SOLVED]

Hi All,

My PCB transformer is getting too hot touch. checked the temp and it is 80oC. Could not find any reason why ? I get an 8 volt at the secondary though its said to be 12v does not seem to be normal for the transformer getting this hot. Replaced the transformer with another but still gets hot. All runs as expected except the transformer and the bridge gets hot.

A visual of the temperature
IMG_0443.JPG

It all looks fairly OK - nothing particularly power hungry.

The transformer is rated 2W - ie about 160mA rms. A 1a bridge should not get hot with that flowing.

Can you break the circuit at the input to the 7805 and measure what curent is actually flowing?

Allan.

A 5volt TVS diode (D11) across the rectified voltage of a 12volt transformer can't be good.
Maybe that should have been an SA15AG (15volt).
Where did you get that diagram again (link).
Don't feel like wading through all your previous (cross) posts of that spotwelder poject.
Leo..

allanhurst:
It all looks fairly OK - nothing particularly power hungry.

The transformer is rated 2W - ie about 160mA rms. A 1a bridge should not get hot with that flowing.

Can you break the circuit at the input to the 7805 and measure what curent is actually flowing?

Allan.

Checked to see that the current draw from the transformer is 300ma ? does not seem like i have components that wold pull that much current. do diodes actaully pull that much current? and yes it was the D11. I'll have to replace that. I did not get a 9vac 2-pri and 2-Sec transformer at the time made the order so i had to get a 12vac, 2-pri and 2-sec. Sadly Newark does not take returns on these. tired selling it off and that did not happen.

So basically after i replaced the transformer forgot about the TVS D11 and that was sinking the extra voltage it was rated for. The schematic is my own.

Thanks wawa for pointing out the TVS D11. So dumb i was.

Hi,

Please do not remove information from posts after it has been solved, where is the circuit diagram that is referring too?

This thread is now of no help to anybody....

Tom.... :o