Looks like there is a line switch for selecting the current loop. Would verify that it is in DC Line.

According to a TT-4 manual on this site.
https://rattrig.com/manuals/tm's.htm

(2) Set the LINE switch of the TT-4(*)/TG and TT-335/TG (fig. 1-7) to Dc line for 60-ma signal circuit operation (operation in a dc system) (fig. 1-3) or to VOICE FREQ LINE for 20-ma signal circuit operation (operation in a voice- frequency system).


On Tue, Oct 4, 2022 at 9:11 PM Kevin H. Phillips <kh-phillips@9-5usa.org> wrote:
To follow up on this message I posted:  I have finally gotten the
machine back to printing from the keyboard.  The problem probably was
oil somewhere it shouldn't have been but the fix took some time.


I tried inserting pieces of paper between the armature and magnets to
absorb any oil.  This did not help (at least at first or as far as I
could tell).


I eventually tried spraying Contact Cleaner (WD-40 brand; it dries dry)
between the magnets and armature.  This did not help. This evening I
started spraying the Contact Cleaner more liberally all over the magnet
area as well as on the electrical/electronic components behind the front
panel.  This began to help.  I kept typing RY's
(one-handed/two-fingered) while adjusting the Range and Armature
controls back and forth.  I spent a lot of time doing this.  All I can
say is that it finally started working properly. I was typing many lines
of RY's as absolutely fast as I could without a single character dropped.


Another thing I tried was reducing the line current via the rheostat on
the front panel.  I turned it down as far as it would go but the meter
would not read below 30ma.  I tried slightly increasing it in stages up
to about 45ma but the magnets seemed happiest at 30.  I may try a TU
with an adjustable loop and see if I can get it lower and see if that
helps . . . or hurts.


It still will not print ITTY.  The loop locks up and I can type on the
keyboard but there is no print from ITTY.  I am going to try reducing
the audio output and see if that does any good.  It is the only thing I
can think to try at the moment.  Maybe the loop current is too high
and/or the signal strength is just higher than these magnets can handle (??)


73

Kevin

W5TTY

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