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

[Dan Merz]

Hi,  I wonder if the same information recommends calibration of the tester
when the 83 is replaced with another 83?  I no longer have the one I-177
that I once had, but I have Hickok 600, 750 , and TV-7 testers.  If I can
find the ss diode sub I made up,  I'll check my three testers with an 83/ss
diode substition  and an ordinary 6L6 to see if there's much difference when
the switch is made.  My 750 shows calibration sticker in 1977 by an airport
agency.  I don't think I've ever calibrated a tube tester and don't consider
it very important in the overall scheme of things.  The challenge of finding
a reference tube for calibration is more than I want to undertake unless
someone has one to pass around along with the "certified" values.  Douglas
provided the steps to calibrate a Hickok tester using a current source
between the plate/cathode pins with the tester set for a 6L6 tube and
providing 5 mA current in the plate circuit.  The only way to tweak the
tester was to shift the position of a magnetic shunt plate on the meter to
change it's sensitivity.  But aside from tweaking the meter,  his test gave
an indication of how well your tester indicated the benchmark reading.
Replacement of bad resistors is the next remedy if the meter is way off.
All this stuff is discussed on Padgett's Hickok page,  which I just casually
checked to see if it mentioned calibration.  In reality, 83 tubes seem to
last a long time (I think I've replaced one in 15 years) so I consider the
ss diode replacement an emergency measure until an 83 can be found.  Maybe I
can find the ss sub and provide a little more info, best regards,  Dan.
-----Original Message----- 
From: r-390-bounces at maiylman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Drew Papanek
Sent: Sunday, March 26, 2006 9:09 PM
To: r-390 at mailman.qth.net
Subject: [R-390] re: I-177 question (OT)


Dan Merz wrote:

>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.   <snip>   He claimed this worked exactly like the 83 in the 
>number of Hickok testers he had >tried. <snip>

The information I have read on this modification states that the tester's 
calibration would be affected and would need readjustment.   IIRC, the 
calibration standard  is a selected 6L6 supplied by Hickok.

Drew


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