To socket or not to socket - TMS9900

[Pepper]

I know reliability comes to mind. But what are the pros and cons of when replacing the TMS9900 that you bung in a DIP socket to make life easier the next time ?

Inquiring minds want to know

 

 

[+Ksarul]

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.

[+Lee Stewart]

Though the TMS9900 does not have as sturdy a pin construction as modern CPUs that routinely use them, perhaps (if there is room) a ZIF socket would be the best choice.

 

...lee

[matthew180]

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.

[Pepper]

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.

[+Ksarul]

Here is one good one, and I buy stuff from this vendor all the time. Here's another one that ends up a little cheaper because it only gives you two (instead of six).

[Stuart]

 

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 November 13, 2017 by Stuart

[Pepper]

 

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...

[+helocast]

Here is one good one, and I buy stuff from this vendor all the time. Here's another one that ends up a little cheaper because it only gives you two (instead of six).

Used both as I keep them in my watch list! Sometimes we're on the same wavelength.