UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 120W PP EL34 amplifier re-born.

dave cox · 27th Sep 2018, 4:46 pm

You'll need to design the regulator to deliver 6.3V into the 'cold' resistance plus a margin. You won't need to spec the heatsink for that much current though, as before its gets super hot the heater will be hot and the load current will drop. On a shorted heater the LM317 will protect itself (but they are quite cheap anyway).

Current limit is 1.5A Min / 2.2 Typ @ < 15V In to out
This implies cold R is less than 4R2 ?

Does that fit with reality ?

dc

27th Sep 2018, 4:46 pm	#18
dave cox Nonode Join Date: Jan 2009 Location: Bristol, UK. Posts: 2,061	Re: 120W PP EL34 amplifier re-born. You'll need to design the regulator to deliver 6.3V into the 'cold' resistance plus a margin. You won't need to spec the heatsink for that much current though, as before its gets super hot the heater will be hot and the load current will drop. On a shorted heater the LM317 will protect itself (but they are quite cheap anyway). Current limit is 1.5A Min / 2.2 Typ @ < 15V In to out This implies cold R is less than 4R2 ? Does that fit with reality ? dc