OTOH BCB rigs, even small ones, had filament control.
Carl
KM1H
----- Original Message -----
From: "Rob Atkinson" <ranchorobbo@gmail.com>
To: <amps@contesting.com>
Sent: Friday, June 15, 2012 9:26 PM
Subject: Re: [Amps] filament instant heating query / simple remedy
> I'm having a hard time believing 3-500 filaments are stressed all that
> much. I'd be more interested in metering the fil. voltage and being
> able to adjust it. I know of no commercially manufactured ham amps
> that meter the filament v. To me that is the amp/transmitter
> equivalent of an oil pressure gauge in a motor vehicle, also something
> you never see in mass market consumer vehicles.
>
> I would not put the all the AC service through an on/off switch for an
> amp. I'd use the switch for the AC to a 28 v. relay coil DC supply
> and use relays for the higher current on/off to the h.v. etc.
> primaries.
>
> 73
>
> Rob
> K5UJ
>
>
> On Fri, Jun 15, 2012 at 8:08 PM, Leigh Turner
> <invertech@frontierisp.net.au> wrote:
>>
>> All good points you make here Jim.
>>
>> When it comes to the small desktop amps like the SB220 and TL922 having
>> separate filament transformers I find that inserting a pair of GE CL-60
>> NTC
>> thermistors in each leg of the filament transformer primary winding
>> provides
>> a simple remedy for implementing a soft-start. The observed glow of the
>> two
>> 3-500Z filaments comes up nice and slow as the thermistors warm up...no
>> big
>> surge in brightness at initial turn on as it was with the stock design.
>>
>> This is in addition to a simple short-duration resistor / AC relay coil
>> style step-start to both the HV and filament xfmrs timed predominantly
>> from
>> the HV electrolytic charge up time constant. This relieves the inrush
>> current surge stress on the front panel ON/OFF switch contacts and the
>> electrolytic capacitor bank.
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1424 / Virus Database: 2433/5071 - Release Date: 06/15/12
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|