G'day Angus.
Sorry for the delay. I missed your email and I'm just cleaning up
my emails and noticed this one.
Yes, the NTC works. I use them in this form for a lot of amps
that I build. See Ebay Item number 402565661699.
They are compact
and work extremely well.
I've never bothered
with soft starts for the little Yaesu amps, as all the Yaesus
I've worked on, have excessive filament voltage at the filament
pins when connected to our AC mains.
A low value of
resistance made up of 5W wirewound resistors in parallel in
series with the filaments brings the volts back from around 6.9
- 7.0V back down to the nominal 6.3V. This resistance, usually
around 0.15 Ohms, also provides a measure of inrush protection
to the filaments. This is very important when using Chinese
valves, which hate excessive volts on the filament.
Cheers from sunny
Binningup, Western Australia.
Alek VK6APK
On 16/11/2024 5:06 am, AngusGM6AGC via
wrote:
Hi Alek,
I trust you are well. Have you
done the step start mod ?¡°A
simple but effective delay can be done with an NTC resistor.
The
primary winding of the transformer is only a few Ohm, so
that a 1Ohm/20A NTC is sufficient to limit the large
momentary switching currents of uncharged HV elco's and cold
filaments.¡±
Is
it effective? Other soft step start arrangements seem more
complex.
I
look forward to hearing from you.
Best
wishes
Angus
?
Bob