> 1. When not abused, transistors are far more reliable than tubes.
I've lost track of the number of times I've had to replace the IRF510 MOSFETs
in my HFPacker 35 watt amp. This is a good little amp, but it eats IRF510
transistors for breakfast. It is Class A, with two devices in parallel.
These power MOSFETs are so fragile that any slight static charge will destroy
them. I am not surprised when small-signal components are static-prone, but
disappointed when "power" components have this issue.
I'm reasonably careful, avoiding unnecessary component handling during
installation, and wearing a grounding strap on my wrist. Yet in one of the
repairs, I replaced both MOSFETs, got no power out, and had to replace them
again immediately!
No tube would be that fragile. If it doesn't have manufacturing defects and
it's operating within design limits, it's likely to work for years. When "pick
up the component in your hand" qualifies as "abuse", you have an issue.
73,
Cathy
N5WVR
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