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Transformer part 2

A project log for RPN Nixie Calculator

A programmable RPN calculator using way too many Nixie tubes

robertcbaruchrobert.c.baruch 04/30/2016 at 22:270 Comments

Went to surplus and got two of the same AC/AC adapters: 120VAC to 14VAC @ 1.5A. I hooked them up back-to-back to see what came out. With 121VAC coming from the wall, I got 16VAC from one transformer, then hooking that to the other transformer, I got 117VAC back out. A 3% loss, which is okay.

Now, in theory, 117 x 1.4 = 164, so I should expect about 162VDC out, assuming 2V diode drop. In fact, I got 155VDC. Measuring the AC input, I found it had dropped to 115.5VAC, which should have translated to about 160VDC. So we're still losing power somewhere.

Well, okay, let's decide to live with this and see if we can light up a Nixie.

Yes. Apparently we can. And interestingly enough, the DC voltage is now 160V, but then we are drawing less power. Which brings up the question: can we load this power supply down with the full 150mA or so? To do this, I'd need about 1k @ 25W, so another trip to surplus is called for. On the other hand, the transformers are rated for 21W, so perhaps the best I'd be able to do is 1.2k @ 21W. We'll see.

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