************************************************************************
			   AUTO-REPEAT FOR THE H19/H89
	************************************************************************


		For those interested in a low-bucks approach to auto-repeat on
	your H19/88/89, take a gander at this. Word processing aficianados will
	appreciate the ability to move the cursor around without having to
	hold down the REPEAT key.


				  THEORY OF OPS

		Diodes D1-D10 monitor the outputs of keyboard plug pins
	14,16,18,20,22,24,26,28,30,32 and clamp the outputs at 5 volts. This
	is input to a dual retriggerable multivibrator(C1), which sets up the
	delay. If, after a delay, the output at pins 4 and 5 are still low,
	they feed a PNP transistor which puts a low out on the repeat
	line (keyboard pin 31).


			       ASSEMBLY

		The circuit uses 1 chip, 1 transistor, 4 resistors, 12 diodes, 2
	capacitors and 1 variable potentiometer.
	Point to point wiring was used, with the entire circuit mounted on a
	1.5" by 3" piece of perfboard attached to the underside of the
	keyboard with stand-offs and sheet metal screws used to secure the
	board. The inputs to the diodes were soldered directly to the lands on
	the keyboard (plug pins 14,16,18,20,22,24,26,28,30,32), as was the
	output going to the repeat function (plug pin 31) using small gauge
	wire. The +5 volts and ground were taken directly off the 5 volt
	regulator using alligator type connectors in the event keyboard
	removal is necessary. The delay time is established by potentiometer
	P1. Adjust P1 until you find the optimum delay for your typing speed.
	There are times this feature may be a liability, especially in game
	playing. Some games have you hold down a key to move a piece on the
	screen, this circuit will not inhibit any functions but the keyboard
	clicking will drive you crazy. Since I have my +5v attached with
	alligator clips, I just pull off one lead to stop auto repeat. An
	alternative would be a small switch located on the back of the case.

		Be careful when attaching the circuit board to the underside of
	the keyboard. There are lands on the reverse side that are difficult
	to see.

		I have found a "bug" of sorts.	After I turn on my system it
	takes a minute or two before the circuit warms up and starts
	repeating. However, this is usually no problem because it takes me a
	few minutes to go through the bootup procedure.

********************************************************************************













			       |	      KEYBOARD		     |
			       |				     |
			       |	      (P 301)		     |
			       |				     |
			       |  14 16 18 20 22 24 26 28 30 32      |
			       `-------------------------------------'
				   |  |  |  |  |  |  |	|  |  |
	       /-D1---|<-----------'  |  |  |  |  |  |	|  |  |
	       |-D2-----|<------------'  |  |  |  |  |	|  |  |
	       |-D3-------|<-------------'  |  |  |  |	|  |  |
	       |-D4---------|<--------------'  |  |  |	|  |  |
      _________|-D5-----------|<---------------'  |  |	|  |  |
      |   |    |-D6-------------|<----------------'  |	|  |  |
      |   *    |-D7---------------|<-----------------'	|  |  |
      |   *R3  |-D8-----------------|<------------------'  |  |
      |   *    |-D9-------------------|<-------------------'  |
      |   |    \-D10--------------------|<--------------------'
      |  Vgrd
      |
      | 			       jumper  13 to 10
      | 	   Vcc		       ________________
      | 	   |		      | 	       |
      | 	   |  R1    C1	      | 	  Vcc  |      Vgrd
      | 	   |-***-+--)|-+      | 	  |    |      |
      | 	   |	 |     |      | 	  |    |      |
      | 	   |	 |     |      |    NU	  |    |      |
      | 	   ____________________________________________
      | 	  |16	 15    14    13    12	 11    10     9|
      | 	  |					       |
      | 	  |		   C1  (74123)		       |
      | 	  |					       |
      | 	  | 1	  2	3     4     5	  6	7     8|
      | 	   --------------------------------------------
      | 	   |	  |	|     |     |	  |	|     |
      | 	   |	  |	|     |     |	  |	|     |
      | 	   Vgrd   |	Vcc   |     |	  | C2	|     Vgrd
      | 		  |	      |     |	  `-|(--|
      `-------------------'	      |     |		`--*@*-----Vcc
			      D11     |     |		   P1
       Vgrd---***--+----\-----|<------'     |
	      R4   |	 \----|<------------'	 Vgrd
		   |	      D12	    _______|
		   |			|  /C
		   |		       B| /
		   `--------------------|<
					| *
				     Q1 |  \E___________>REPEAT
					       |	(pin 31
					   R2  |	 on keyboard)
				      Vcc--***-'
	  SYMBOL DEFINITIONS:
	  -------------------

	  ---***---	RESISTOR
	  ---*@*---	VARIABLE POT.		     |	/Collector
	  ---|(---	CAPACITOR		Base | /
	  ---|<---	DIODE		       ------|<      TRANSISTOR
	  Vcc		+5V D.C.		     |	*
	  ---|(---	CAPACITOR		     |	 \Emitter
	  Vgrd		GROUND
					       ________________
					       |	      |  I. C. CHIP
					       |______________|



		    PARTS LIST
		    ----------

	  D1-D12  SIGNAL DIODES, 1N914
	  R1	  27K  OHM RESISTOR
	  R2	  400	"     "
	  R3,R4   1K	"     "
	  P1	  100K MINI POTENTIOMETER
	  C1	  .01 uf DISK CAPACITOR
	  C2	  10  uf CAPACITOR
	  Q1	  PNP TRANSISTOR, 2N3638 (or equivelant)
	  C1	  DUAL RE-TRIGGERABLE ONE-SHOT, SN74123


	  ####################################################################

		There are numerous ways to implement auto-repeat in your
	computer, each with varying degrees of sophistication. This circuit
	was chosen as the most direct solution to the problem. The design
	credit goes to Ronny Toups, an inveterate hardware hacker who would
	rather tinker than eat, drink, or sleep. If you have any questions, try
	reaching me at home (214-385-1367), or leave a message on the DF/W HUG
	BB. (214-742-1380)

			       ANDY PALUCH
			       Dallas/Fort Worth Heath Users' Group
	EOF  AUTORPT.DOC