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To socket or not to socket - TMS9900


Pepper
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I tend to socket any chips I remove as a general rule, as it limits potential damage to board traces over the long term. I just use gold plated machine-pin sockets when I can find them. They are a bit harder to find for the 64-pin 9900 chip, but I just looked in my parts box and turned up about 20 of them, so they are out there.

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I would not use a ZIP socket. I don't think they are designed for long-term mounting of chips, and they are expensive. Also, I can't remember ever having to replace the 9900 CPU itself, so a ZIF socket for such a rare event would be overkill, IMO.

 

If a 64-pin socket cannot be found, you can always use SIP pin headers.

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I would not use a ZIP socket. I don't think they are designed for long-term mounting of chips, and they are expensive. Also, I can't remember ever having to replace the 9900 CPU itself, so a ZIF socket for such a rare event would be overkill, IMO.

 

If a 64-pin socket cannot be found, you can always use SIP pin headers.

SIP pin headers will work nicely, they are very handy !

Finding a 64 pin DIP that is 2.54mm pitch seems to be hard on eBay, but Mouser has them.

I need to go through troubleshooting this spare board that I have again, before I start unsoldering everything. The -RESET line is set high all the time... which makes me suspect the TMS9900.

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I need to go through troubleshooting this spare board that I have again, before I start unsoldering everything. The -RESET line is set high all the time... which makes me suspect the TMS9900.

 

Have you tried replacing the TIM9904 clock chip which generates /RESET? (May be a 74LS362 on very early boards.) It is sometimes already socketed which makes life easy.

Edited by Stuart
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Have you tried replacing the TIM9904 clock chip which generates /RESET? (May be a 74LS362 on very early boards.) It is sometimes already socketed which makes life easy.

No I've not tried replacing it yet. It's not socketed on this board.. (My working TI99/4A is lol). I'm going to do more poking around before unsoldering the beast...

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