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Help needed with Aiwa TPR-300A auto stop mechanism

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#1 928S

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Posted 12 March 2014 - 05:30 PM

I'm nearly done with cleaning and rebelting my TPR-300A but I am rather confused by the auto stop mechanism. I was wondering why, upon reassembly, the tape deck would not function nor would the amplifier come online. Upon doing some basic voltage tracing I found that the leaf switch that turned on the deck and engaged the amp was not engaging. Why was this so? It turned out that the auto stop lever was not engaged in the upward position thus pressing the leaf switch together.


The auto stop mechanism is activated by a cam which is driven from the main drive belt. This cam, when it hits the auto stop lever, pushes it upwards thus engaging the leaf switch and starting the deck. What confuses me, though, is that since the cam is driven off of the main drive belt, the cam will move past the auto stop lever thus bringing the auto stop lever down and shutting the deck off.


When I put the deck into "play" the right (when looking at the deck from the rear) spindle's motion causes the auto stop lever to duck out of the way of the approaching cam.


How does this all work? How does the deck stay engaged during play/FF or RW? Is there any adjustment I should do to correct this potential issue?


Attached are some photos of the mech. The first photo shows the lever and cam setup. The lever and cam are located just to left and below of the plastic drive wheel located in the middle left of the photo.








#2 Beosystem10

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Posted 13 March 2014 - 03:42 AM

It shuts off when there's no cassette in there but, if you look at the opposite face and the edge opposite the heads, you'll find another little toggle and that keeps the reed switch closed when there's a tape loaded. When that tape reaches the end of a side, the greater tension on the mechanism sees to it that the cam won't drop out of the way of that reed switch so it then stops as it should.


These auto stop mechanisms are like all of the world's greatest ideas; simple yet totally effective. The one in the B&O that inspired my forum handle, although Hitachi-sourced, is identical in all but name to the one you have there.

#3 928S

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Posted 13 March 2014 - 02:17 PM



Thanks for the information. I'm having trouble finding that toggle. What is puzzling me is that when I engage play with a tape in the deck nothing seems to be moving mechanically to push the auto stop lever up to close the reed switch. In this case the deck will never engage.


I've enclosed more photos of the deck including one showing a tape inside the deck itself.