Jump to content

Pepper's Photo


Member Since 9 Sep 2017
OFFLINE Last Active Yesterday, 12:41 PM

Posts I've Made

In Topic: To socket or not to socket - TMS9900

Mon Nov 13, 2017 7:24 PM


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... 

In Topic: To socket or not to socket - TMS9900

Sun Nov 12, 2017 6:49 PM

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.

In Topic: NanoPEB is not always recognized.

Sun Oct 29, 2017 8:26 AM



On a side note, I see that you have the PiDP-8 kit :) I build one myself and I have it running Seti@home 24/7  :grin:

Yes, I have the PiDP8/i running a Mystic Telnet BBS. I also have the "blinkin lights" going ;)

I occasionally play Adventure on it also.

I'm looking forward to building his PDP11 clone when that comes out.

In Topic: NanoPEB is not always recognized.

Sun Oct 29, 2017 7:38 AM

Have you tried another power socket in the house (e.g. preferable a different circuit).  


Yeah, I tried all of the above. New CF card, reformatted and loaded the vol1 back onto it, etc.

I ended up returning it to the person I bought it from. I suppose, It's not beyond the realm of possibilities that it's my TI that's the issue. Not the NanoPEB.

As I only have one working TI99/4A, I did not have anything to test against. When I get my spare unit working then maybe I'll purchase another NanoPEB. Until then I have plenty of other projects to keep me busy. 

In Topic: NanoPEB is not always recognized.

Fri Oct 20, 2017 6:44 PM

I took my 12v regulated Bench power supply and dropped the voltage down to 5V with a DC-DC Buck converter. Still the same symptom. So that rules out the PSU as that's been 3 different sources.

Cleaned the sidecar board contacts with some fine sandpaper. No joy.

It's not going to beat me ... well hopefully not ..lol.