Mountain Computer Music System hardware fix

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amauget's picture
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Mountain Computer Music System hardware fix

Hi all,
I'm trying to use a Music System into an Apple II+.
I got the message "** ERROR ** MUSIC BOARD NOT IN MACHINE  PRESS SPACE BAR WHEN READY" when trying to use the card with the software.
I have tried different disks images, different motherboards, different slots. I even bought another Music System. No luck.
Then I look into the manual, always RTFM :-)
At the beginning, there is a notice stating that if you encounter my problem (and others) you have to install a little board with 100 pF capacitor at location B11, where a 74LS08 is. I'm trying to figure out how can I reproduce this board. Anyone has information about it ? Pictures would be welcome.
Thanks in advance !

_____

Antony

Apple II forever

tokabln's picture
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Hi Antony,

Hi Antony,

I believe you should PM @stynx... as he used to have a lot of musical cards.

 

when taking a look at the manual from asimov... I tend to believe that the 100pF condensator is tied to Pin 1 & Pin 7 of the 74LS08... which is worse to try without having such adapter board.

 

https://www.ti.com/lit/ds/symlink/sn54ls08.pdf

 

 

 

stynx's picture
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Joined: Apr 19 2012 - 09:41
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Hi Antony,

Hi Antony,

 

since i have never encountered your problem, its a bit hard to determine the source of the error. 

 

The CMS is a DMA expansion and will not work with any other DMA card or modification. This means, that any accelerator will make the CMS unusable. Certain other cards like the TRI-Card serial/parallel expansion may render the CMS (party) unsuable as well. Also if too many expansion cards are installed, the card might not work reliable. The CMS stops the Apple II every second clock and runs at around 512Khz. If the card cannot start, it may result in the mentioned error (although i have never seen that one). On the CMS there are some SRAM chips (2111A) for configuration, maybe they are defective? Maybe you have the CMS cards in the wrong order?

In regards to the B11 mod. I suspect that the PHI0 line is modified by the 100pf cap. Try replacing the B11 chip with a 74F08 series IC first. If that does not help, try a 74AS08. I doubt, that this will actually help, but try it anyways. Do you have an Apple IIe? Try that one, maybe you have a later CMS and they can be a bit buggy in early Apple II (everything befor RFI).

If nothing helps: reseat each chip on the CMS and check the chips with a chip-tester.

 

-Jonas

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