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MMD > Tech > Ampico > amp52.htm

Ampico B Rewind and Repeat System
Ampico B Rewind and Repeat System

    Referring to Fig. 27, it will be seen that valve D which controls the switch pneumatic, and also the repeat pneumatic, only has suction supplied to it from valve C during reroll when the repeat switch is set at "On" or when the 5B hole in the tracker bar is open.

   Repeat Switch at "On."    As the end of "reroll" when the tapered end of the roll uncovers the groove in the take-up spool, the pallet control lever drops into the groove and causes pallet 2 to be raised.  Atmosphere through the lower hole under this pallet springs valve D which has a supply of suction due to the fact that pallet 4 is open and connected through the repeat switch.
    Under these conditions the repeat pneumatic rapidly shifts the transmission to the "play" position before the ring disengages from the take-up spools and before the constricted switch pneumatic has collapsed.  When the note sheet starts ahead it pushes the pallet control level out of the groove.
    As soon as this lever is pushed from the groove, the valve D dips and the switch pneumatic returns to its open position.
    When repeat switch is turned to the "Off" position, the tube leading from pallet 4 to valve C is cut off.  This valve C can now only be controlled by 5B tracker hole.  The tube leading from pallet 1 to the "reroll" speed pneumatic is also cut off.

    Repeat Switch at "Off."  With the repeat switch at the "Off" position, on rewinding, when the last 15 turns of paper remain on the take-up spool, slowing down does not take place as the tube leading from the lower hole under pallet 1 is closed by the switch.  In this position, the full suction supply is continued on the "reroll" speed pneumatic until the end of the roll.
    When the tapered end of the music roll uncovers the spool groove as it unwinds from the spool, the pallet control lever drops into the groove and positions pallet 2 to operate the valve D.  Valve D however, does not operate at this instant as it has no supply from valve C.
    When the paper uncovers the 5B hole, atmosphere admitted to the valve C causes this valve to supply suction to valve D.  The atmosphere, already communicated to the valve D pouch causes it to raise and admit suction simultaneously to the repeat pneumatic and the switch pneumatic.
     This operation taking place so late allows the paper to unhook from the take-up spool.  The transmission is immediately moved to the "play" position and the switch pneumatic slowly collapses and shuts off the electrical power.
    This method of controlling the switch pneumatic is a precautionary measure.  Should the ring pull off the music roll, or should the repeat fail to function, the player will automatically shut off.
    The operating block under pallet 1 is in correct adjustment when it allows its pallet to close its holes when there are 15 turns of paper on the take-up spool.
    The operating block under pallet 2 is in correct adjustment when it allows the pallet to close its holes just before the control lever is pushed out of the groove in the take-up spool by the paper.
    This adjustment can be made very accurately by turning the contact screw in the operating block.

    In starting a roll the electric switch is turned on by hand, but when the roll is rewound and free from the take-up spool, this switch is shut off automatically.
    When it is not desired to "repeat" the playing of the roll, the note sheet rerolls at full speed throughout its length, disengages the ring from the take-up spool, then automatically resets the transmission to the "play" position and shuts off the electric switch.
   When it is desired to repeat the playing of the roll, the note sheet rerolls at full speed until about 15 turns of paper remain on the take-up spool, when it slows down for the rest of the way, and before the ring is disengaged from the take-up spool the transmission is thrown back into the "play" position.
    Under these conditions the switch pneumatic, which requires about 5 seconds to close, does not have time to function before the note sheet is wound around the take-up spool again and the pallet valve controlling the switch valve is returned to its seats.
    The pallet valves which control the operation of the electric switch also control the operation of the "repeat" mechanism, so the two are very closely related.
    During "reroll" when there are 15 turns of paper left on the take-up spool, the pallet control lever causes pallet 1 to be raised from its port; atmosphere through the port negates the suction being supplied to the reroll speed pneumatic through the No. 65 constriction.  This causes the reroll speed pneumatic to open and allows the roll to reroll slowly from this point.
 
    It is a great convenience to have the levers set automatically in the "play" position and to not have to wind the note sheet around the take-up spool.
    It is unnecessary to hold the reroll level when turning on the electric switch.
    As will be seen, the mechanism for accomplishing these various functions is fundamentally extremely simple and not liable to get out of order.
 


Reproduced from pages 52-54,
The Ampico Service Manual 1929,
Copyright 1929 by American Piano Company


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