Hello All:

I have an I-177-A tube tester and a Munston MX-949 A/U adapter, which
has a more modern 9-pin socket. I also have a full set of maunals
thanks to Nolan Lee and his website.

The I-177-A tester gives readings for 6L6-type tubes that are right in
line with what I would expect. (Around 5000-6000 micromhos.)

Using the MX-949 adapter, I am now trying to test several 12AX7,
12AY7, and 12AT7 tubes. But here's the problem: With the dial
settings specified in the test data tables, I seem to be getting Gm
readings that are not close to the readings given in various tube data
sheets.

Here are the dial settings I am using for 12AX7 tubes:

Fil: 12.6 volts
A: 4
B: 2
L: 0
R: 19
MMHOS: 3000

At these settings, a known good 12AX7 gives a Gm reading of around 700
micromhos for each of the two sections of the tube. That seems too
low.

If anyone has information on what a typical correct Gm value should be
for a 12AX7, 12AY7, 12AT7, and 12AU7, I would appreciate your
response. I would also appreciate input from others with an I-177
tester and MX-949 A/U adapter as to what the correct L and R dial
settings are for these tube types. (The manual could be wrong.)

Thanks for the help.

--E