I-177 tube tester reads 2-3x to high on gm.
 

Well since I am boxing the loose tubes I have, guess I had better test
them! I have a military I-177 Made by Daven that sez that the gm of
the tubes is 3x higher than it should be. A 6K6 should be 1600 but I
read 4200!!! Pins the needle on the 3000 range and reads 4200 on the
6000 range. All known good tubes tested read high. I do not see a pot
or adjustable power resistor to change the calibration. Looked @ the
calibration info on the Hickok 600 series, but is too different to
apply to the I-177. Any ideas? Anyone have the calibration routine
for the I-177? The mil manuals I have found do not have a calibration
routine.

Thanks
Randy.

I-177 tube tester reads 2-3x to high on gm.
 

"AB9GO" ha scritto nel messaggio oups.com...
Well since I am boxing the loose tubes I have, guess I had better test
them! I have a military I-177 Made by Daven that sez that the gm of
the tubes is 3x higher than it should be. A 6K6 should be 1600 but I
read 4200!!! Pins the needle on the 3000 range and reads 4200 on the
6000 range. All known good tubes tested read high. I do not see a pot
or adjustable power resistor to change the calibration. Looked @ the
calibration info on the Hickok 600 series, but is too different to
apply to the I-177. Any ideas? Anyone have the calibration routine
for the I-177? The mil manuals I have found do not have a calibration
routine.

Thanks
Randy.

I do not know which is the story of your tube tester. A possibility is that somone replaced the two wire-wound potentiometers with others of different values (it happened to me!). It is VERY difficult to find a replacement for them. One is a 3000-ohm potentiometer having a non-linear taper, the other one consists of two ganged low-value potentiomers. I would check them with an ohmeter before proceeding to isolate the fault.

73

Tony I0JX

I-177 tube tester reads 2-3x to high on gm.
 

Randall, the I-177 tube tester uses 3 shunts for 3 ranges of gm measure.
My I-177 was defective, the shunts were broken, so the measure was not ok.
These shunts are near a switch, as I can remember.
The repair was done a lot of years ago, so control by yourself !
bye from Piero ( ex I1SPO, ex I5SPO).

"AB9GO" ha scritto nel messaggio
oups.com...
Well since I am boxing the loose tubes I have, guess I had better test
them! I have a military I-177 Made by Daven that sez that the gm of
the tubes is 3x higher than it should be. A 6K6 should be 1600 but I
read 4200!!! Pins the needle on the 3000 range and reads 4200 on the
6000 range. All known good tubes tested read high. I do not see a pot
or adjustable power resistor to change the calibration. Looked @ the
calibration info on the Hickok 600 series, but is too different to
apply to the I-177. Any ideas? Anyone have the calibration routine
for the I-177? The mil manuals I have found do not have a calibration
routine.

Thanks
Randy.