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

[Dan Merz]

Hi,  the substitute for 83 type tube described by Douglas for use in a
number of Hickok tube testers used two 1N4007 diodes and two 10 ohm/1 watt
resistors.  Connect the proper end of one diode to pin 2 and the proper end
of the other diode to pin 3,  and join the other two ends of the diodes.
Connect the joined ends of the diodes to pins 1 and 4 via a 10 ohm resistor
to each of the pins,  all mounted in an old tube base.  He claimed this
worked exactly like the 83 in the number of Hickok testers he had tried.
The two 10 ohm resistors are in series across  pins 1 and 4 (the filament
pins) and their midpoint goes to the joined ends of the two diodes.  Without
looking at a tube tester schematic,  I'm not sure exactly why the two
resistors are wired this way but it works.  I think I tried the wiring in
one of my testers but reverted to the 83 when I found one.   If the hookup
isn't clear from my description,  I can scan a diagram he included to
clarify.   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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