[GreenKeys] Model 33 ribbon advance constantly on

[Troy Peterson]

On 30/05/2022 13:59, Ethan Blanton wrote:
> Troy Peterson via GreenKeys wrote:
>> I've finished completely cleaning and re-oiling my model 33 ASR, and
>> after checking everything over as best as I could I decided it was time
>> to get things moving again so I've put the motor back in and put the
>> belt on. Here's a short video of it:
>> https://youtube.com/shorts/dcXCMkHSOyU
> That is normal behavior for "running open" or "spacing".
>
>> This is just the printer section motor running directly from AC off of a
>> variac. It's only running at around 90v and drawing between 1 and 1.5
>> amp.  One thing that seems odd to me is the ribbon ratchet seems to
>> continuously feed forward. Is this normal?  The hammer is moving, but
>> not actually striking the printhead and I believe that to be normal in
>> this state but it seems strange that the ribbon would always spool when
>> it's not printing...  Does the ribbon always continue to feed (and
>> autoreverse) on these machines when it's running?
> I believe that is normal.  Because there is no current on the loop, it
> is continuously "receiving" a start bit, followed by eight zero bits,
> as far as it knows.  It is therefore "printing" a NUL byte, which does
> suppress the hammer blow, but is otherwise orienting the print
> head/etc., as if it were printing a character.  Every time it prints,
> it advances the ribbon a bit.
>
> You should be able to stop the spacing by providing current for the
> current loop.  I don't know about the 33, but for my 35 ASR, a pair of
> AA batteries and a 150 ohm resistor drove the current loop just fine
> and locked in the magnet; however, the 35 has an internal regenerator
> and I do not know about the 33.
>
> Ethan

Thank-you, (And to Alf Fisher as well for the same answer) - That makes 
prefect sense and is completely logical.

Cheers,
Troy.