[Amps] 572B - News?

[Tom Osborne]

I had a FL-2100B and did the bias mod that RF Parts recommended.  It 
worked fine with the Svetlana tubes after that.

Before the mod, right after I put the tubes in, I keyed the amp with no 
drive and it pegged out the meter and ruined 1 tube.  RF Parts replaced 
it for free and sent me the modification.  73
Tom W7WHY




On 11/7/2014 11:24 AM, Dave wrote:
> The service bulletin was in the bias system for the FL-2100B.   Improper
> bias triggered instability.  There were not RF related changes.The FL-200Z
> has a different bias system but I don't remember if it fixed the problem.
> The problem does not exist in the 30L1 or the SB-200 .All the details are on
> the Web.  I Svetlana's plate dissipation rating is 160 watts, just like the
> 572B.  Yes, the plates are smaller but they are also thicker and are made of
> graphite like the original T160 (original nomenclature for what became the
> 572B.  I have a set of original ceramic base 572B in my 30L1 and they have
> worked perfectly for over 5 years of daily use and the amplifier is stable
> on all bands.  I wish I had bought a spare set back when they were current
> production.
>
> Dave
> W7VM