Generator GN-38
Used in EE-8, BD-71/2, RM-29A etc.

This is the remains of an EE-8-A that we learned magneto theory on in A&P school.
The GN-38 and MC-131 were mounted at opposite ends of a board.
They were wired direct so the bell rang when you cranked the generator.
I reassembled the parts and the result is the complete bottom half of the phone.
GN-38 is a handcrank magneto generator.
It is used to create ringer current in field phones.
GN-38 (From TM11-330 pg23)
Crank Gear Ratio = 1-5
Output Frequency at 1000 rpm of armature
(200 rpm of crank) = 16 cycles
Output current at above speed:
200 ohm res = 90 milliamps
1000 ohm res = 50 milliamps
10,000 ohm res = 9.5 milliamps
Open circuit voltage (approximate = 100 volts)

GN-38 type descriptions
Generator GN-38 has three small cobalt steel
permanent magnets arranged in two pole faces
about an armature.
Generator GN-38-A has a rotating magnet
with stationary coils.
Generator GN-38-B has two stationary magnets
and two pole pieces arranged alternately
about an armature.
GN-38 variations
All 3 have the same gears.
GN-38A has a different switch
(because of stationary coils.)

GN-38 compared to GN-41
GN-41 is used in EE-91.
GN-41 appears to be a
4 magnet version of a GN-38.
GN-41 coil is longer and
most likely has more current capability.

created 02-23-2009
Last Update: .