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

[Dan Merz]

Hi,  there was a substition of ss diodes published in Antique Radio
Classified by Alan Douglas for Hickok testers, subbing for the 83.  As I
recall a resistor in series with each diode was involved and it was put into
a tube base to be plugged in as a replacement.  I'll try to find the
article; the index for the 20 years or so issues that I have is not good.
Douglas was quite familiar with the testers and I'm sure the sub worked just
as well as the 83.  Dan. 

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of W. Li
Sent: Thursday, March 23, 2006 12:27 PM
To: R-390 at mailman.qth.net
Subject: [R-390] re: I-177 question (OT)

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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