Modification for OBD0 Application

Modification for OBD0 Application(while we make a version 2 of the board)

Okay then, here goes. This is just one way of doing it. I´m sure someone can come up with a much cleaner way, but this was how I did it. Needless to say, this is not my own design... l3st4rd is the evil genious here, not me Very Happy

You will need the following: -PCB, resistors, sockets, pins, NVSRAM etc. as found in the excellent current kit (as sold by joshuavillasenor) -1 pcs 74LS86N TTL chip -1 pcs additional 10K ohm resistor -Some thin insulated wire for making interconnections on the board

How-to build/modify the board itself: -Cut the connections marked RED in the first picture -Assemble the RTP as per the excellent instructions in Wi Ki -Cut or break off all pins except 4,5,6,7 and 14 from the 74LS86N (see picture 3) -Solder the 74LS86N on top of the 74LS00 (piggy backed!) - but ONLY pins 4, 7 and 14. -Bend the remaining pins 5 and 6 upwards so you can solder wires to them. -Using thin wire, make the connections as indicated in the first and second picture. The chip shown is the 74LS86N. This assumes of course that it is soldered on top of the 74LS00 as shown in the Wi Ki directions. -The resistor shown(or rather, crudely drawn!) in the second picture is 10Kohm

Shielding (optional): One of the connections made is pin 2 on the 3-pin header. If you make this connection, you will have a nice ground signal for connecting to a shield on a shielded cable. The A15 signal for which pin 2 was originally intended is now connected elsewhere.

Connecting to the ECU: You will need to isolate pin 16 from the ECU. Sorry no pictures, as I don´t have my ECU with me at the moment. -One connection must be cut going to the 24-pin SRAM on the top of the board. -Another must be cut on the bottom of the board. -These two points must be re-connected so that only the ECU pin is "disconnected" and the rest of the circuit is complete. -Connect one RTP wire to pin 16 on the ECU (connect this to the INPUT on RTP) -Connect one RTP wire to pin 21 on the 24-pin SRAM (M5128)

That´s all I have time for now - hope it helps.

/Bindegal