lemonjelly
New Head-Fier
- Joined
- Feb 16, 2012
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Hi lemonjelly.
Are we really OK? As gibosi has mentioned, aren't they separate windings for anodes and heaters? I remember TrollDragon voicing concerns over the transformer if higher rated resistors are used...
Cheers!
Hmm I'm learning this stuff as I go, so I needed to check this a bit more carefully. The VA rating above is correct for the entire transformer, so the transformer can handle that amount of power and the resultant heat, but obviously the question is whether the winding itself can manage. Apparently if you don't use the heater windings, then it does mean you can use more current in the HT winding, as the transformer is cooler due to not using those windings. It's pretty hard to work out exactly how much leeway this gives you however - it's definitely not as simple as I assumed above - but it seems like really about 50% extra or so would be realistic (so 150mA HT). You're OK so long as no part of the transformer gets so hot that you can't keep your hand on it from the sounds of it (a transformer dies when it gets so hot the laminations between windings melt and the transformer shorts).
+ I know that I had the transformer at over 180mA and it was hot, I'd say probably fairly close to as hot as I'd want it, but it still worked fine. And that's with my wooden/acrylic chassis whereas a stock amp would have the metal casing as a heatsink. So yep it's still a risk, but I think it's much less of a risk than I thought before... as in the transformer is pretty close to being in spec (maybe slightly over but nothing like as over spec as I thought it was before) and the resistors probably also are over/@ spec, but they're likely to last for a decent amount of time (but this is where I'd expect failures really).