hot transformer

[chopchip]

in the miniblok 2 amp design Fred uses furnace controler transformers. i built two of these. on the one a transformer becomes much hotter than the one on the other. it is the second TX that gets hot, the first one sees the current from the filaments. i checked it with a series light bulb and it lights up as the caps load up and then goes dark.

why does the TX get hot on the one but not on the other. it's not so hot that i cant touch it though.

any explanations?

[kevinkr]

Originally Posted by chopchip

in the miniblok 2 amp design Fred uses furnace controler transformers. i built two of these. on the one a transformer becomes much hotter than the one on the other. it is the second TX that gets hot, the first one sees the current from the filaments. i checked it with a series light bulb and it lights up as the caps load up and then goes dark.

why does the TX get hot on the one but not on the other. it's not so hot that i cant touch it though.

any explanations?

Measure load current and see if it is the same on both, otherwise some difference in the quality of one transformer vs the other is the likely culprit.

Note that it could be either of the transformers on the hotter running of the two chassis. Measure primary and secondary currents of the first transformer in each as well as B+ current - that should tell you which is responsible.