power transformer heat

[tenderland]

Icompleted my first 2A3 amp and it works well. Everything seems at an exceptable temperature however the power transformer seems pretty hot after the amp is on for over an hour. being that this is my first amp
I have no concept of how hot or cool it should be.


Jeff

 

[gingertube]

Sweeping Generalisation from 30 years experience - If you can't hold your hand on it for 10 seconds its too hot.
Cheers,
Ian

 

[tenderland]

hot

I would say it is rather hot than.If the amp was built to specs
and seems to be working well otherwise ,what can be done to cool it down a bit , air holes on the chasis around it ?



Jeff

 

[kmtang]

I think you have to check and measure the voltages and currents in the circuit. This would give you good idea if the transformer is overloaded.

 

[EC8010]

Air holes around a transformer are unlikely to help cooling. But you could indulge in a spot of dual monolithic avicide (kill two birds with one stone) by adding a new transformer specifically for the audio valve heaters. In the UK, you can buy transformer kits from Maplin that have a split bobbin with a ready-wound primary and an empty chamber for the secondary. You then wind your own secondaries. You can gain some important advantages:

(1). Wind the 2.5V (2A3) windings with a centre-tap to help reduce hum. Do the same for the other heater windings, too.

(2). You no longer have capacitance from the HT windings to couple rectifier switching noise to the sensitive heater wiindings and thence to cathodes.

Oh, and.

(3). The reduced load on the existing transformer wil almost certainly allow it to run cooler...

 

[dhaen]

Appalling humour, but works in more than 1 language

dual monolithic avicide

°ìÀÐÆóÄ» one stone; two birds

 

[ray_moth]

I once built an amp in which the power transformer became too hot. It was fully shrouded with silver-coloured (bright cadmium?) end caps. I painted it matt black to assist radiation and it ran somewhat cooler after that.