UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Advice needed on choosing a power transformer

zeerust2000 · 17th Oct 2016, 9:53 am

Hi everyone,
I'm presently planning to clone the valve stereo amplifier in a 1968 unit I have, which sounds great to me. It has a 6V4 rectifier, and each channel uses 1/2 of a 12AX7 and a 6M5 power valve. The 6M5 is very close to an EL84. In fact they can be substituted for each other, apparently. My question relates to the power transformer. In the original unit, the secondary HT winding gives 520 VAC unloaded (ie, with rectifier valve removed) and around 495 VAC with the circuit load. So, would it be reasonable to use a Hammond transformer rated at 450 VAC? I'm assuming here that this figure is for a unit under load, as this appears to be how the Hammond specs are given. Any advice will be greatly appreciated. Cheers...

17th Oct 2016, 9:53 am	#1
zeerust2000 Retired Dormant Member Join Date: Sep 2016 Location: Sydney, New South Wales, Australia. Posts: 2	Advice needed on choosing a power transformer Hi everyone, I'm presently planning to clone the valve stereo amplifier in a 1968 unit I have, which sounds great to me. It has a 6V4 rectifier, and each channel uses 1/2 of a 12AX7 and a 6M5 power valve. The 6M5 is very close to an EL84. In fact they can be substituted for each other, apparently. My question relates to the power transformer. In the original unit, the secondary HT winding gives 520 VAC unloaded (ie, with rectifier valve removed) and around 495 VAC with the circuit load. So, would it be reasonable to use a Hammond transformer rated at 450 VAC? I'm assuming here that this figure is for a unit under load, as this appears to be how the Hammond specs are given. Any advice will be greatly appreciated. Cheers...