frank@dciem.UUCP (Frank Evans) (04/27/86)
I have tried to create a BREAK key for the TRS100 in order that it could send a typical BREAK signal to our host computer to let it know we wish to get on line. The electronic boys looked at the TRS100's schematic and came up with this setup. This is a switch that when you press on its button,I believe causes a 5 volt signal to go thru lead 2 of the RS232. To make a BREAK Key on the Trs100 you will need the following: - 4 point 'star' tip screwdriver - 2 - 5 inch pieces of fine insulated wire - a small low wattage soldering iron ie < 35 watts - the smallest micro 'Momentary On' pushbutton switch that you can find First, you have to open the computer.To do this first flip the computer over and undo the 4 screws on the underside of the computer. Next turn the computer back to its normal position and lift the top off. Note the top is stuck on rather snugly!! The keyboard should now be able to be tilted over to the right. With the computer facing you, just as if you were using it,you should now have the top of the circuit board exposed to you. We will call the top end, where the output jacks and RS232 are,'North'. The 'South' end is where the space bar would be. This leaves the 'East' on your right side and the 'West on your left or where the 'Bar' reader jack is. Now at the North end about 1 1/2 inches south of the RS232 jack is a chip called M35 on the circuit board. The chip is about 1 inch long and lies in an east/west direction. It has 14 pins, 1 to 7 on its south side and 8 to 14 on its north side. Just south of chip M35 is a resistor labelled R75 and it also lies in an east/west direction. Now taking two pieces of very small gauge wire about 5 inches long solder each piece to the following. 1)Solder one end of one wire to the end of pin 7 (most South/East pin) of chip M35. 2)Solder one end of the other wire to the west end of the resistor, R75. Now if you were to ** MOMENTARILY ** touch these two free ends of the wires together you would cause a Break signal to go out thru the RS232 jack!! I believe it sends a 5 volt signal thru lead 2 of the RS232 and this works!! To produce a ** MOMENTARILY ** contact with these wires, you must use a Momentary On push button switch. This is a switch that when you press on its button it creates a temporary contact between each of the wires soldered to its two terminal ends. When the switch is not pressed, an internal switch spring keeps the switch constantly in an OPEN mode/position ie. there is no contact between the two wires. You should be careful when you solder the fine wires to the chip and resistor. Your soldering iron should be a very low wattage ie <35 watts. Also you should just heat up the solder and touch it to the wire and chip pin for as short a time as possible. All these precautions will help prevent any over heating of the chip. Secondly, make sure you, your soldering iron and the computer board are all connected to a common ground in order to reduce the risk of static. I mounted my micro 'Momentary On' push button switch to the North end of the cabinet just west of the battery area. There is a little bit of space here so you can drill a small hole and mount the micro switch. This is a good spot since it prevents any accidental pressing of the switch and the carrying case is not likely to always press on the button draining the batteries, if that is possible? Well, I hope this proves helpful to some of you. If it does work then I would appreciate it if you could drop me a line to let me know. If it doesn't work for you then maybe your device is looking for the BREAK signal on a different pin on the RS232. GOOD LUCK!! Doc Evans!