On Mar 16, 2005, at 5:14 AM, Pete Smith wrote:
> I understand that running 3-500s on their side risks internal shorts.
I ran a fil-on 24/7 test with a horizontal 3-500Z to determine filament
sag. The sag rate was quite slow -- which was determined by grid-fil
BDV. It appeared that rotating the tube 180º every 1000-hours or so
would have prevented any fil-grid clearance problem.
> I
> need to do some trouble-shooting on my modified SB-220's relay/bias
> switching circuit, however, which would be much facilitated if I could
> key
> but not drive the amp (no RF out) with it upside down. I can pull the
> tubes if I need to, of course, but would prefer not to.
Operating 3-500Zs base up or base down is okay. In a SB-220, most of
the hot exhaust come out the left side of the cabinet, so upside down
should be no problem.
>
> 73, Pete N4ZR
> The World HF Contest Station Database
> was updated 12 January 2005
> 2868 contest stations at
> www.pvrc.org/WCSD/WCSDsearch.htm
>
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>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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