Hamann 505

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Repair Info

This calculator was in a very nice condition but not operational.  It took 6 month before it finally functioned as it should.  

While working on it I found:

One of the blocks was caused by a steel axis going through a aluminium bearing.  Corrosion almost welded them.   I had to dismantle the multiplication unit to solve that problem.

Besides these mechanical actions the spark reduction circuit had to be renewed.  All capacitors were ever removed and had to be put back in place.

The importance of motor speed adjustment:

On this machine proper speed adjustment is necessary.  In case of a multiplication a carriage-left movement is started immediately after the last turn of the main register.  The carriage movement has its own electrical switch that only comes in after the carriage movement has started.  Therefor the first part of carriage movement must be taken care of by the main shaft rotating several degrees before it actually stops.  If the motor speed is too low, this movement stops before the carriage switch is closed.  As a result the carriage doesn’t move back to its starting position after a multiplication.  It may easily happen that the carriage stops in an intermediate position between two defined positions.  In that case the machine ends up in a blocked mode.

Adjustment is done with the set-screw on the back of the motor using the strobe disc on the main shaft and a proper 50 Hz light source.  A smart phone with a strobe app works fine.  Turning the set-screw to the right raises the speed and v.v.

See assets page for additional information regarding:


Register I removed

Register I removed C’up


Multiplier unit removed

Multiplier unit