Siemens MAMMOMAT 300 Parts Replacement page 16

3 - 4
•
Ensure that the potentiometer with its metal enclosure does not fall out of the carrier
bracket (Fig. 4) and place the Teflon pulley onto the potentiometer shaft in such a
position that the noose of the cord, wound counter-clockwise a bit onto the pulley, can
just be hooked back to the hex socket head screw. Hold the pulley and continue with
winding the other cord about four (4) turns/windings of 360°, then hook the lower end of
the spiral spring back onto the rectangular bracket. (The upper end of the spring will be
just some 3 cm from the pulley).
Fig. 8
•
Attach an ohmmeter to soldering lugs 1 and 2 of the new potentiometer. As an alternative
the corresponding contacts on compression device end of the now disconnected and
freely accessible connector X874 can be used (Fig. 5).
Adjust the measured resistance applying a screwdriver through the hub of the pulley to
the groove on the end of the potentiometer shaft (Fig. 6). Start from a lower resistance
value and turn the screwdriver clockwise until reaching 230 Ohm + 20 Ohm. On the side
of the pulley, mark the exact position of the groove (Fig. 7).
•
Hold the potentiometer in place (Fig. 8) and drive the slide manually upwards. During
this, look through the pulley hub and observe whether the shaft turns clockwise exactly
as the pulley does, and whether the groove and its marked position on the pulley
coincide. Help with a screwdriver if the pulley, fixed only lightly, does not turn the shaft.
In order to turn the pulley enough to get access to the grub screw, the slide has to go up
about two (2) cm.
When the grub screw becomes visible from the front, press the pulley gently towards the
carrier bracket and tighten the grub screw with the Allen key 1.3 mm (1/Fig. 9).
•
Drive the compression slide manually back into its lowest position and check the
resistance value again to ensure that it is within tolerance. If necessary repeat the
adjustment: For this the grub screw has to be loosened (see previous work step).
M300/1000/3000/3000 Nova
Service
Procedure - Potentiometer R863
Fig. 9
SPB7-230.841.03
Rev. 02 04.04
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CS PS 24
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