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Hi Jay
Look at the transformer makers website for suggested fuse ratings.
You should not need a big fuse as the caps are small. Have you measured the current taken from the transformer secondaries, it may be you have messed up connecting the 2 power supply boards and have some strange short going on.
Check the mains current when running, does it come to about the right amount?
Say DC current times DC voltage times 1.6 is about output power times 2 for being inefficient plus say 2 watts for transformer losses.
Rather than a NTC you could simply wire a 39 Ohm 25 watt 'gold block' resistior in series with the mains. It will lower the AC into the transformer a bit but for a preamp it probably won't matter.
Matt S
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