HP-41 82161A HP-IL Tape Reader - Doesn't work anymore - Help Needed

[albertofenini]

Thanks everyone for the help, but we have a bigger problem ... which is why we changed the title of the post

We wanted t try to read a program from the demo tape and we discovered that the Tape Reader
does not turn on anymore.

Doesn't with only the battery, doesn't with the battery and the charger,
but without battery and with the charger when we move the switch to the ON position just the BATT led turns on
but nothing more (hope we didn't fried anything by doing this)

Obviously we have tested the charger, the battery, tried different ones and the problem is not there

So we opened the unit and we found the switch traces very dirty (see pic)
We cleaned them as they were kind on joint together, so we separated with the tip of the exacto as these should be.

However, when we connected the unit together, nothing, it still does not work.

We don't have the schematics for this unit, I have checked on the Schematics site,
but I have only found those for the HP-IL Printer, I'm wondering if the PSU is similar.

Also, we have found on the bench a strange small button (pictured with a rubber so that you can see proportions), that we don't think is coming from the unit, but you never know.

Has anyone have experienced a problem like this and tried to repair the Tape reader ?
Thanks for help !!!!

P.S. we have noted that the upper left corner and the bottom left corner of the switch traces are
like connected, with a very low resistance (6 ohm) which may be correct since
there is actually a big resistor of 5.6 ohm the connects that two but we don't know if it is ok