[GreenKeys] Capacitor underneath keyboard - Model 19...

[E.]

Hi all,

After nearly three-quarters of a year of looking at my broken Model 19 - afraid to dive in... I finally dove in and actually, things aren’t all that complicated as I thought (hopefully).

First off, a little background.  Last year when I first got it, I got a little excited and hooked up my DC supply to see if the thing worked (without any resistors - the power supply said it was self-adjusting to current).  The keyboard was set - I believe - to keyboard and tape.  The keyboard didn’t work (I believe - it’s all a blur) but the bulb lit and the DC side seemed to work mostly.  With the keyboard not working, I flipped the switched down to tape punch only... the power supply surged to 1A - a small, burning smell wife around and everything on the DC side has been dark ever since.

I’ve suspected for a while that the problem is on the keyboard side… so today I did some multimeter measuring on the keyboard - the parts that I didn’t have to cut wires for (to begin with).  Mostly everything checked out… the punch magnets checked out at 19 ohms each, the counter magnets & release magnets for the punch all checked out at 500 ohms each, the two resistors on the underside of the keyboard (towards the back) checked out at 100 ohms each (I assume because they are in series), the resistor on to check at 350 ohms… but the large capacitors underneath the keyboard - front side, underneath that protective packet that unscrews, checks out at around .270 nF each when they should be at 1uF each (seen on the attached diagram towards the bottom).  I don’t have much experience with capacitors (neither does my wife), so could these two be part of the problem with the dead DC and if so, could their malfunction possibly have led to a problem elsewhere on the teletype (any general ideas where to start if so)???

Thanks much all and happy late summer!!!

Sincerely,
Eric :)


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