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Thatvalveguy · 13th Apr 2018, 12:14 am

I decided against posting this in the Sussex topic, to keep that topic uncluttered.

Anyway, so here it goes, i was thinking about designing a DC supply for the Sussex homebrew valve testers as transformers tend to have relatively poor regulation. DC can easily be stabilised with one of the abundant three terminal regulators. These however tend to be quite inefficient to say the least. A friend of mine told me you could build a efficient switching pre-regulator for linear regulators see the attached schematic. I ended up using a BC558 and a 1n4148 instead of the P channel Fet.

This ended up keeping the voltage over the linear regulator at about 1.1V, the LT1084

Today i tested a LT1084 based regulator, I had a board with LT1076 laying around, this isn't the most efficient device, but for testing functionality it should suffice. Surprisingly enough it works quite well, noise is quite high, partly because its a switching regulator and partly because i didn't have the correct inductor for the LT1076

Attached you will find a scope plot of the supply starting up into the cold heater of a 6P3S-E, a 6,3V 880mA tube.

Calculated efficiency is about 68% at 20V in 6.3V out. With a better device than the LT1076 efficiency would be over 80%

13th Apr 2018, 12:14 am	#1
Thatvalveguy Triode Join Date: Apr 2018 Location: Nijmegen, Netherlands (You know from that bridge) Posts: 35	DC heater supply valve tester. I decided against posting this in the Sussex topic, to keep that topic uncluttered. Anyway, so here it goes, i was thinking about designing a DC supply for the Sussex homebrew valve testers as transformers tend to have relatively poor regulation. DC can easily be stabilised with one of the abundant three terminal regulators. These however tend to be quite inefficient to say the least. A friend of mine told me you could build a efficient switching pre-regulator for linear regulators see the attached schematic. I ended up using a BC558 and a 1n4148 instead of the P channel Fet. This ended up keeping the voltage over the linear regulator at about 1.1V, the LT1084 Today i tested a LT1084 based regulator, I had a board with LT1076 laying around, this isn't the most efficient device, but for testing functionality it should suffice. Surprisingly enough it works quite well, noise is quite high, partly because its a switching regulator and partly because i didn't have the correct inductor for the LT1076 Attached you will find a scope plot of the supply starting up into the cold heater of a 6P3S-E, a 6,3V 880mA tube. Calculated efficiency is about 68% at 20V in 6.3V out. With a better device than the LT1076 efficiency would be over 80% Attached Thumbnails Last edited by Thatvalveguy; 13th Apr 2018 at 12:44 am.