Quote:
Originally Posted by retailer
After unwinding the filament supplies I spent a few hours looking for a way to reduce the winding height - slightly smaller wire - the maths showed that I could get both 17 turn filament windings on the one layer - bobbin 33.5mm wide 0.9mm wire (actual diam 0.95) but in practise I found I could only get 16 turns on for each filament winding.
The end solution was to use 0.67wire (actual diam 0.71) and wind 2 wires together for each filament supply, overall current carrying capacity was just a shade under that of a 1mm diam wire, but the final winding height was reduced enough for me to finish off with 2 layers of insulation and still fit the laminations without help of the G-clamp.
With the transformer assembled on the bench the no load magnetising current is 50mA, once bolted in and powered up the HT sits at 370V and each filament supply measures 6.6V, I'm reasonably happy with the final result.
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That does look good, nice work.
Joe/Ed, is there a rule of thumb we can use with AWG (off the top of my head, there is a relationship between each gauge going up/down) where we can sub a single wire to use bifilar or trifilar etc.
Eyeballing the filament wind work retailer did it looks like 19AWG can be subbed with 22AWG, 3 gauge difference,
If we take it further, as a minimum for an OT secondary, can we use, eg 5 x 23AWG winds wired in parallel (sandwiched between pri winds) for a single 16AWG wind.
The rule of thumb = required gauge (eg 16AWG) + 5AWG (parallel winds) + 2AWG (constant?) = 23AWG
Doug