A couple of weeks ago Tom Rauch told me that in such a case, secondary
voltage would be limited by core saturation. Maybe you only applied 10-20%
overvoltage to it if it limited. But it sounds like it went much higher, if
the lamps were noticeably brighter like that.
Years ago it was common practice to "rejuvenate" old TV picture tubes by
cooking the cathodes at a higher-than-normal voltage. I don't remember how
high, but it actually worked to improve emission.
Jerry W4UK
At 02:17 AM 1/4/2002 -0800, Mike wrote:
>Would there be any long term detrimental effect of running
>very high filament voltage on 3-500Z for a few seconds. I was
>testing a Drake L-7 here and forgot to jumper the filament
>transformer for 240V (jumpers were set for 110V). I realized
>my mistake after having the amp on for about 2 seconds and
>shut every down (the bright panel lights and fast running fan
>gave it away). After I set the jumper properly and fired the
>amp up again, everything seemed to play okay - full output on
>all bands. Not sure what the 3-500Z's actually saw during that
>short period as I suppose it depends on the winding resistance
>of the filament transformer. Worst case would have been
>around 10V. Hopefully the filaments didn't really have time
>to overheat signifcantly, but I don't really have any experience
>with this sort of thing.
>
>This all reminds me of the time I dropped a good 3-500Z
>on a concrete floor. I should have watched TV with my wife
>tonight.
>
>73 de Mike, W4EF...........................................................
>
>
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