Today I broke out my first build, a 5f1 Mojotone amp that I put together several years ago and decided I'd check out the voltages and bias, when I noticed that the 6.3 VAC heaters only measured @ 5 VAC with 120 VAC applied. I figured there must have been an issue with my wiring but I didn't see anything obvious so I disconnected both green and yellow filaments to test the filament lines out of circuit. I first measured resistance and got .3 ohms for both green and yellow filaments and when powered with 120 VAC, both filaments were near identical voltages. Green: 5.53 VAC Yellow: 5.49 VAC So I guess my question, is this normal for these champ power transformers (Mojo 760) to have these kinds of similar readings on both heaters? And what effect would running it at this low voltage for the heaters have on the circuit? Considering pretty much all other voltages in the amp are much higher than normal with modern 120 VAC? The amp does work alright but it has always had a slight bit too much hum for my liking, which I have previously tried to resolve through increased power filtering, shielded cable, and bi-passing the volume pot switch to no real resolution.