[Amps] switching power supply for tube amplifier

[Peter Chadwick]

I find it interesting that over the last 20 years, I've had more solid state failures than tube failures.
Ok, I have only 11 valves (tubes)  in the main HF station and an awful lot more semiconductors.. Of the 11 tubes
1 was bought in 1936 (6L6G)
2 were  made in about 1944 (6SJ7, VR150)
2 were made in the late 1940s (5R4G, 6X5)
2 were made in the early 1960's ( QY4-250 , similar to 4-250A)
4 were made in the early 1980s  - 3 off 6146B, 1 off12BY7A
Those last 4 have worked hard in several contests and many pile ups.
Since 1985, failures on tubes - nil.
Semiconductor failures - 17.  Such things as IC's that died for no apparent reason -  although 4 of them were caused by metal corrosion, according to the failure analysis guys at work - I work for an IC company..
Latest was last week, where a ULN 2803A octal Darlington driver rated at 500 ma, switching 150mA, decided to have a saturation voltage of 9 volts.
I've had such things as an JFET lose gm, for no apparent reason.
3 cases of second breakdown in transistors, although everything says that they were well within limits.
There can be advantages in having a semiconductor failure analysis lab handy, staffed by people who owe you a favour or two!
So I wouldn't really want a switcheing PSU at HV.
73
Peter G3RZP