the alpha syntauri system
  a ancient synthisizer concept for the Apple II
   Page No.:H212-4
           at this page we will examine the back card of the
   Mountain Computer Music System,
I/O card


 In this part iīll show the details about the second rear card of the system.The cables to the external devices are connected to this card.
 The most simple part of the external devices is the lightpen. In fact itīs just a simple phototransistor that detects light and then it switches
 the power just like any normal switching transistor. The only difference is that instead of a voltage to the baseconnector in this transiostor
 has a lens at the base and the light causes the transistor to switch through. The Transistor is a MRD370. The pen is visible in the picture
 below of the card.

 The other 2 cables are ending at chich connectors which are common within audio systems. Both cables together act as stereo output -
 one cable contains signals for right channel and the other contains the signals of the left channel. The output level is equal to standard
 audiosystems and equals to 0,7 Volt which is normalelly feeded to line inputs at the amplifier.So the part of the electronis on the card in
 position front ( left side ) of the holes where the cablebinders are located bear the analog electronic part of the board. The other part of
 the card contains 2 function blocks: The part that sychronizes the lightpen with the video output - it muist detect exactly the millisecond
 where the pixels are generated in the picture that  display that area which shall be selected by the user. In that very moment the pixels
 get displayed the transistor passes over a switching pulse to the card and the card must pass over that detected signal to the software
 for the further handling and switch to the selected menuitem.

 The other part of the electronic at the card the pulses setup by the soundconfiguration is prepared before itīs handed over to the audiopart.
 This primary audiopart determines such things like frequency, pulseduration and other parameters that have been selected by the software
 and passed over to the other frontcard. The connector on the top of the card passes over that data to this card.

  So in a very unique way you may call the first card ( front card ) to be the part for handling software and memory storing the parameters and
 menuoptions and at this second card ( rear card ) there is a kind IO handling and a kind of synthisizergeneration for waveforms.

 here is the view to the populated side of the second ( rear ) card:

 and here is the view to the soldering side of this second ( rear ) card:

 and here is the view to the "external" connection parts of this card : the light pen and the 2 audio-output- connectors.

 so next here a view inside of the lightpen - it only contains a lightsensitive switching transistor :


Here is the componentlayout of the card:

 And here is a view to the solderside after it has been converted to be blue layer for later analysis of the card:

 So now here is the red layer from componentside:

 and here is the combination of both layers together:


So finally here is now also the circuitplan of the second card of the Mountain Computer Music System :


       As explained in the previous page the connection between both cards in my system was not reliable.
Therefor i replaced the connection in my system with goldplated extended pinconnectors.
The following pictures show this replacing solution. In the first picture i have placed both cards apart from
each other to mahe the connection visible. In the second and third picture the cards are both plugged together
and set in their default slots.

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