Well I found the answer in some old email. It is because I have an ASR set with the keyboard sync pulse magnet.

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I got the clue about the pulse magnet from the Navy C school notes, which are very helpful. In sync pulse systems, the signal generator clutch only gets kicked off by the pulse magnet, after the code bar release closes the pulse switch. So if you swing the pulse magnet disable lever into place, the signal generator clutch will always get tripped when the code bars release - even in T mode. Sure enough the electrical portion of the K-KT-T switch disconnects the pulse magnet when in T mode. Once I moved the pulse magnet disable lever, my T mode works exactly like it should, with no signal generator action. You learn something new every day - I have disabled the pulse magnet on other keyboards, but they had always been KSRs, not an ASR.

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And who wrote this helpful info? It was me back in 2018 when I previously wrestled with this.

The great thing about a lousy memory is that there are so many interesting things to re-discover.....

Nick England K4NYW
www.navy-radio.com

On Thu, Feb 29, 2024 at 2:55 PM Nick England <navy.radio@gmail.com> wrote:

In "T" mode, the keyboard signal generator clutch is not supposed to engage, meaning that the keyboard mechanically activates the perf but does NOT transmit a signal on the line. This allows you to cut a reply tape without interference while the page printer is printing an incoming message.

My problem is that the perf is getting activated/reset fine in T mode, but unfortunately the keyboard signal generator clutch is also getting tripped, causing the keyboard signal generator to interrupt the signal line. This means I can cut a tape OK, but that printing of an incoming message gets garbled.

I can't figure out how to adjust the keyboard control selection lever so it does not trip that clutch. The control cam is causing the perf to activate/punch/reset correctly in T mode, and I can see that the keyboard control selection lever is rotated, but that dang clutch trip lever is still tripping.

Note - I can't actually see the end of the clutch trip lever as it is buried in there somewhere.
- reference position C on Figure 21 of 573-117-100 - (diagram attached)

Any suggestions? I swear this thing used to work properly but something has happened and I can't figure out what.....
Nick