Interesting that this recent discussion of filament supply regulation is
taking place at exactly the same time that I have a new amp project under
way. When I went to the parts cupboard for a filament transformer, the
cupboard was bare! So rather than go out and actually buy a transformer (it
is mind boggling how much those have escalated in cost) I have decided to
build an electronic regulator and use a non-standard low voltage transformer.
I will use a full-wave triac bridge with a zero-crossing integral cycle duty
cycle controller for virtually noiseless switching.
The whole thing will fit on a small PCB of very user-friendly construction.
If I could get a small handful of interested people to join me in this
project (particularly those of you who have amp projects going now, or wish
to upgrade previous one) I will make a first class commercial grade PCB with
copies for everyone. The estimated parts cost will be under $10 (probably
under $5, depending on your filament current needs.)
If you are interested, send me an email with your filament voltage/current
needs. If I get a critical mass of volunteers, I will be able to do the whole
thing in 10-15 days.
Eric von Valtier K8LV
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