[Boatanchors] Question: X-Rays from 3B28?

William w_b_morton at hotmail.com
Fri Feb 13 22:42:24 EST 2015

Hello All,

Been thinking of using a pair of 3B28 tubes to rectify an output voltage to around 450VDC.  That value is above the critical anode voltage value of 50V, so that should not be a problem.  Current is less than the 500mA max listed in the table.  With the output voltage far lower than the ~1000V values listed in the table, I think these things would not even break a sweat.

Two questions for the experts:
1.  Any issue seen operating arund 450VDC?
2.  The tubes have a sticker on the base with a warning regarding x-rays.  Why is there a warning on the tube base but nothing shown on the data sheet?

I had no idea these would present an x-ray risk based on what I saw (and did not see) on the data sheet, so I picked up a pair.  Perhaps this my learning experience for the week.

Have a great weekend!

Best Regards,


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