Bob, I will soon continue the assembly of an ST70 I pieced together from parts around the internet (sorry, I collected the parts about 4-5 years ago and didn't know about you at the time). I somehow found in my parts box a 1N2389 rectifier. I am curious to try it. Are you familliar with this device? It seems to be a pair of diodes in a metal can, the size of a small metal tube and wired to replace the usual types like 5U4, 5AR4, etc., and similar to a Weber Copper Cap without the time delay feature. Looking on google came up with specs of 600mA and 1600PIV. So I'd guess it could handle being in a stock ST70?
Would it be appropriate to use it instead of a new production 5AR4? I have a couple of new 5AR4's, but I keep reading of short life spans and fireworks when they go.