[R-390] re: I-177 question (OT)

[W. Li]

I have a nice I-177 tube tester that serves me well. I
recommend Nolan Lee's notes on calibration and
maintenance found at http://www.acadiacom.net/nlee/

My question pertains to the Type 83 mercury vapor
rectifier. Although it was designed to operate
upright, it is actually mounted on its side in this
particular tester. Clearly therefore, some care is
needed in use by letting it warm up for 10-15 minutes
to prevent internal flashover. 

My question is about converting this to a solid state
device. 

Replacement 83's are not exactly easy to find....
Inspecting the schematic, the HV takeoff is from the
mid-point of the 5V filament winding. So is there an
issue by removing the tube, and inserting two silicon
3A silicon rectifiers between this point and the plate
pins 2 and 3?  I would leave pins 1 and 4 unconnected
to anything.

The other question is in regards to the 5Y3GT
rectifier. Why does Nolan not recommend a solid state
conversion here? It *looks* like the same sort of
circuitry here. Obviously, 5Y3's are a lot more
plentiful than 83's which makes that conversion less
pressing.

To my thinking, one advantage of converting both
rectifier tubes to solid state could be insuring
balance in both arms of the HV windings. The others
are immediate startup, and significant decrease in
heat and energy consumed. 

Am I missing something in this line of thinking?

PhiIosophically, I am more interested in preserving
functionality of my gear than preserving *history*. 

Thanks

W. Li
Mercer Island, WA


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