MEMORY PLUS Manual By Lee Davison and Hans Otten Back to The Computerist

			MEMORY PLUS Testing and Field Repair
         
	Your MEMORY PLUS board has been burned in and tested before shipment.  If,
	after following the steps outlined in the "Setting Up MEMORY PLUS" section,
	the board does not seem to work properly, or if it ever seems to stop
	functioning correctly, then the following steps should be taken.

	  1.	Check that the board is receiving adequate power.

		Place the ground lead of a voltmeter or 4scope on any convenient
		ground on the board (the left lead of the large capacitor at the
		upper left hand corner of the board is handy) or on the connector
		(A-1, E-1, E-22, E-A, or E-Z).

		Measure the +5 volts at each of the four jumpers on the Header
		located near the voltage regulators.  If you are providing
		unregulated +8 to +10 volts, then the top jumper should have this
		value.  If you are using regulated +5 volts, then the top jumper
		should show +5V.  The bottom three jumpers should show +5V in any
		case.  If not, check your supply.  If one of the three shows a
		voltage other than +5, it indicates a problem with the associated
		voltage regulator which might require replacement.  The bottom jumper
		comes from Q6, the next jumper from Q5, and the next to top jumper
		from Q4  (See diagram on page 25).

		Measure the +25 volts at pin A-22 of the MEMORY PLUS application
		connector.  If you are providing unregulated +27 to +30 volts, the
		output of the +25 volt regulator circuit should show about +24.7V.
		If you are providing regulated +25 volts at this pin, it will show
		the output of your power supply.  If the value for the unregulated
		situation is not +24.7, then check your unregulated voltage at pin
		E-2 of the MEMORY PLUS expansion connector.  It must be +27 to +30V.

	  2.	Check that all IC chips are firmly in their sockets.  It is possible
		for chips to come loose during handling and shipping.  Push each chip
		firmly into its socket.

	  3.	Check that the Header is in the proper position for the method of
		providing +5 volts.  If you are providing +5 at pins E-21 and E-Y,
		then the Header should have its notched corner at pin 9 and the
		jumper wires should go from pins 2 - 15, 4 - 13, 6 - 11, and 8 - 9.
		If you are providing unregulated +8 to +10 volts at pins E-19 and
		E-20, then the Header should have its notched corner at pin 1 and the
		jumper wires should go from pins 1 - 16, 3 - 14, 5 - 12, and 7 - 10.

	  4.	Check all of the connections between the MICRO, MEMORY PLUS, and the
		power supplies.

	  5.	Follow the instructions in the "RAM Memory Test" section if the RAM
		Memory appears to be having problems.


	  6.	Check the MICRO or try MEMORY PLUS with a different MICRO.  For EPROM
		Programming it is absolutely essential that bits 0, 1, and 2 of the MICRO
		Port B are functioning properly (PBO, PBl, and PB2).  A quick test of
		Port B may be made by putting FF in location PBDD and then trying to
		write 07 in location PBD.  If this does not work, then you have a
		problem and should not attempt to program any EPROMs until you have the
		MICRO serviced.