>At 09:00 AM 11/4/03 -0800, rlm < > wrote:
>>**** The SB-220 has a current-limiting type filament transformer which
>>limits inrush-I to 60% of what Eimac allows. However, a stepstart is
>>still needed because the inrush-I to the HV-transformer will eventually
>>ruin the SB-220's ON/OFF rocker switch.
>
>
>What's "eventually?" My SB-220 has been around 30 years so far, and is
>still running the original switch.
*** Pete -- Do you start it on the CW position? Does it run from a
20A, 240V circuit?
>Of course, I don't cycle it every QSO
>-- seems as if I have read that the 3-500Z's filaments don't have a rigid
>filament life expectation like indirectly heated, more modern tubes, so
>there's little reason to shut them off. True?
*** the useful emissive life of the 3-500Z cathode is c. 20k-hours at
4.75V and c. 2k-hours at 5.25V.
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