[Amps] SB220

[R.Measures]

>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.