[Amps] switching power supply for tube amplifier

[Peter Chadwick]

Steve said:
>Earlier this year we had the first field failure, at just under 3.5m 
accumulated operating hours<
There may well be a distinct quality difference between the discrete power transistors you used there, and cheap plastic packaged op amps.
For example, at Plessey some 20 odd years ago, we had a problem with certain devices from one batch failing from corrosion in in 6 months. Turned out the Philippines assembly house used a different epoxy filler with long glass rods that allowed water in by capiliary action. Of course, they hadn't said anything......
A bit like the WW2 R1155 aircraft receiver for the RAF, where a batch was built by some company using acid flux, and they all rotted in 6 months!
73
Peter G3RZP