Smith Corona Messenger Module Repair

[aef0]

I recently purchased a 'Smith Corona' messenger module. A device which is supposed to interface RS232/Serial or Centronics LPT printer to a Smith Corona typewriter. And allow it to function as a printer. The goal of which is for another project.

When I plugged in the device, stupidly, without testing the components first, I was greeted with a nice puff of blue smoke. After opening the case and exposing the board, it appears that an inductor has burnt out.

I understand that inductors burning out tend to be caused by another inline component, I've placed an order of all the capacitors on the board, however my question is this:

How could I determine what rating the inductor was? It appears to say 10uH, but I believe there may be more to it than that? It looks like the inductor is in series with the large 1000uf capacitor, thus making a LC / tank circuit? Is there a way to work backwards to determine what the component should be?


[Left side of photo (bottom) has been flipped horizontally to overlay with the top side of the board]

[rsaxvc]

Did the caps help?

I also noticed it looks like the circled component may have overheated too.

A few different typewriters use something like a 5V Uart from typewriter to box, then the converter box does RS232 or parallel conversion to 5V UART. We have a Smith Corona 250 at my folks place, I may take a peek inside and try to see if there's any indication how this comm link works.

[wasedadoc]

That coil appears to be in series with a power input from the connector.  The coil's output end has that large electrolytic to ground and also goes to one leg of that metal tabbed device. which is probably a linear regulator though I didn't find anything Googling the part number on it.  Too much current because the electrolytic has shorted or going into the regulator (or transistor).  Shorting to ground regulator or something after that.

Coil value is not critical.  Just there to reduce noise coming in or going ot.