[Amps] New Amplifier

[Catherine James]

> 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