Tom
>
>The best thing you can do for the TL-922 is get rid of the series
>connected filaments by replacing the filament choke and
>transformer.
>
? Why?. My TL-922 produces no audible hum-modulation on SSB. I hear no
hum-modulation from other 922s. Henry has been using seriesed filaments
for years.
>Even though the series-connected filaments have a "voltage
>equalizing" connection that connection has enough resistance to
>allow one filament to have more voltage and dissipate more power
>during turn on.
? Perhaps -- if the filaments are not of similar resistance. In my 922,
there is 0.01Vrms difference between the filaments.
>
>A second problem with the series filaments is if tubes become
>unbalanced in dynamic characteristics the dc anode current return
>path can superimpose a little hum on the signal.
>
? never one of 'em.
>Series connected filaments are bad enough in Christmas lights,
>they are dumb in a PA with 150 dollar tubes..
>
? How could it be "dumb" if it works ok?.
>Lacking that mod, a slow start for the filament is a good cure,
>because the voltage and current will rise slow enough that the
>filament start-up dissipation in each tube stays reasonably close..
>
? Why? Using the same core, a 5.5v winding can produce 2x the peak
amps than an 11v winding can.
- later
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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