[GreenKeys] 28ASR Selector Magnet Driver and "Blinding"

[Robert Goff]

Hi John and the group,
The printer locks up, like it would in steady mark condition, as soon
as I turn on the power on, and it stays like that despite anything I
do: transmitting with the TD or breaking the signal line manually or
with the break key.

I've tried a couple different printers with the same result. The
perforator works fine. Putting a millammeter in the loop I can see the
needle move from keyboard keying or the TD, but no change in that
steady mark output from the SMD.

I'm thinking that SMD is just bad. I've got a copy of Spec 50042S
which has quite a bit of servicing info, so that is going to be the
next step: pull the LESU out (sigh!), disconnect the SMD and get it on
the bench.

Thanks to all for you help!
de Robert
W7MKA

On 6/20/21, John, W9DDD <w9ddd at tapr.org> wrote:
> Good morning Robert,
>
> Could you describe the symptoms is greater detail?  Is the printer doing
> absolutely nothing, or is there some motion going on, but no printing?
> In what position is the print suppression code bar?  If it kind of goes
> through the motions but never prints you may have a situation with  a
> similar solution to the one for the sync pulse problem. Is there a
> solenoid on the left side of the printer?
>
> If there are no signs of anything going on then about all the documents
> about the blinding are in the link I gave you earlier off list.  I've
> never run into anything that documented the source of the blinding
> (doesn't mean it's not there is some of the Navy versions of docs).  It
> would be either stunt box contact (but I don't think blinding yourself
> really works too well), a relay or a switch since it has to be an
> isolated contact.  Any relays unaccounted for?
>
> ---
> ----
> The above comments or recommendations are SWAG. Use at your own risk.
> John, W9DDD