Hi Chris,
See the ON Semiconductor TDA1085C Data Sheet / App Note...all the needed
info' is succinctly contained there.
Leigh
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Chris Wilson
Sent: Tuesday, 25 June 2013 6:55 PM
To: amps@contesting.com
Subject: Re: [Amps] Miller-Larson effect on thoriated tungsten filaments
/neat electronic soft-start
> Yes those GE CL-60 NTC inrush limiting thermistors are helpful albeit
> still yield a fairly fast rise time constant in the filament voltage. The
> far gentler slow 3 to 4 second ramp up from the Triac controller is more
> elegant. The slow soft-start circuit is based on the ON Semiconductor
> TDA1085C IC chip and a 40A Triac.
>
> In fact I've also got a couple of CL-60 thermistors (one in each leg) the
> primary of the Kenwood TL922 amp's filament transformer to trim /
fine-tune
> the steady-state filament voltage measured right at the tube socket to
circa
> 4.9 Volts, as the factory stock filament voltage is on the high side;
around
> 5.2 to 5.3 Volts. That slight over voltage can also shorten the 3-500Z
tube
> emission life.
>
> Leigh
25/06/2013 10:24
Do you a schematic you would share for the Triac soft start setup
please Leigh?
Thanks.
--
Best Regards,
Chris Wilson.
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