[R-390] Bright BallasTube

[Drew Papanek]

On excessively bright BallasTubes Barry wrote:

>My experience is that they don't glow much after power-up.  The ballast may
>be good but you may have excessive current draw.  Since you replaced nearly
>everything else that could affect that, I strongly suggest you check the 
>two
>tubes involved -- especially the one in the PTO.  Yes -- lightning
>(element/filament shorting) does strike twice, (Phil found the previous PTO
>tube shorted).  Two possible reasons,  offhand -- continued bumping/moving
>of the PTO as you were adjusting the linearity and/or the replacement tube
>may have come from the same lot with a latent defect.
>
>Now that things are settled in, test those tubes again in the tester.
>Normally it's not best practice to leave them in the tester too long, but
>let them sit and tap as you go through the shorts test.  Another
>possibility -- something in the wiring harness.  Maybe you should measure
>the current draw with the ballast in place.
>
>Do others agree about the bright ballast situation?

It also is possible that heater strands in PTO or BFO 6BA6 could be shorted 
to one another and not to cathode.  You might check voltage at PTO and BFO 
tube heaters while in the radio.  Since it is unlikely that this type of 
short would occur in both tubes (Murphy's law notwithstanding) it would show 
as unequal voltage division between tubes.  Make sure that BallasTube is 
really a 3TF7 and that PTO and BFO tubes are really 6BA6's (hey, maybe 
someone stuck 3BA6's in there, the 600 mA current specification would really 
light up that 3TF7).

Drew

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