So I snipped off the offending diodes, and replaced the dropping resistor and voila! we are no longer blowing fuses and voltages are back in spec. We don’t know what damage may have been caused by those damn things… I stuck in a real 6X4 rectifier and I still get the loud hum.

To add to the fun, a buddy of mine, the guy who came up with ‘Paleo-Electronics’, found the Weber Copper Cap rectifiers. These are the RIGHT way to do solid state rectification. They are simply tubes with solid state components, but done right, they protect your other tubes in a way that diodes can’t.

In a tube rectifier, high voltage is not passed until the tube warms up. As the tube gets closer to temperature (various widely, but well under a minute) it produces more voltage. It’s not until the tube reaches operating temp that it puts out full power. This is a good thing because the other tubes are also warming up. If they get full voltage before they are warm, they can damage the tube immediately or at least have their lifetimes seriously curtailed.

The Copper Cap rectifiers mimic this warm up with what I assume is a capacitor network inside the bottle. They even mimic ‘sag’ (the failure to produce full power when driven hard and quickly) although that is a conversation for another time.

You can get them here

I tried swapping the Weber out vs. the Original 6X4 I had in my other GA-5 and while I could hear a slight difference in the reaction to hard fast strumming, that was it.