Monroe 8N-213

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Repair Info

The overall condition of this machine was quit good. However, to get this Monroe operational again took a lot of time.  The major cause was  disrupted synchronisation.  The result was that with EnterDIVD  the keyboard was reset before the digits were entered into the lower register and that EnterMultiplier mostly didn’t enter anything. As a result division nor multiplication were possible.


An important part of the timing in this machine is determined by  a set of 8 gears. The gears are positioned on either side of the main carry shaft gear (see picture below).  Loss of synchronisation can easily happen.  In the picture below, it’s sufficient to loosen the one-screw fixation of the main carry shaft (1), lift it a bit and move the connected gears, one on each side. Having done that, synchronisation is gone.

There are position markers on the gears, but they are hardly visible and worse: having them aligned didn’t result in proper functioning. However, in the end I got the machine fully operational.

To improve visibility of control the keyboard was removed.  The procedure can be found in the assets page.


The arc suppression capacitor needed replacement (see picture below).  A  0.15uF/1000V-DC version out of my stock didn’t live very long. Probably it died from high peak currents.  Next, I replaced it with a 0.1uF/50 Ohm arc suppressor.  This may not be the best spark reduction solution, but will suffice for machines which are only occasionally used for demonstration in stead of daily use.


Front-open-NoCar-as.jpg FrontLeft-open-NoCar-as.jpg Right-open-WithCar-as.jpg BackLeft-WithCar-as.jpg BackRight-NoCar-as.jpg Back-NoCar-as.jpg CIMG1412as.jpg Bottom-NoCar-as.jpg CarBottomRight-as.jpg CarUpperRight-as.jpg CIMG1333-TimingWijzigen-s.jpg ArcSuppression-s.jpg

Timing

Arc suppression