A New Display with a bright LED Back light

One of our users (Michael Kirk) found this bright LED backlit display that will work in the K1000 keyboard and perhaps the modules as well. With a little care and work, this display drops right in the keyboard and unlike the EL backlit displays will not fade over time. If you put one of these into a module, be sure to let us know if there are any major differences in the process.

Michael's overall process and discussion:

I found this on the Jameco web site ( www.jameco.com ):

Jameco Part 365982 PICVUE PVC160206QYL04 $11.95
DISPLAY,LCD,3.3X1.2,PARALLEL,16X2,5X8DOTS,YEL/GRN BKLGHT

It is almost identical to the original Seiko M1632 display in terms of dimensions, voltage, input signals, signal timing, and display commands except for the following:
- Back light is LED type and needs +4.2 volts at about 100 mA
- benefit is longer life
- Display contrast (pin 12) cannot be grounded as done with M1632 display (contrast too dark), but must be controlled with variable resistor (or pair of fixed resistors) to set the desired contrast value.
- Display is 4 mm thicker than M1632 due to LED back light - discarding the plastic spacers on the mounting bolts and using the metal bend tabs of the display 'shroud' provides proper clearance.

Michael's method:
- This LCD does not come with right angle header connector. You will either need to buy new or remove from the old LCD. Mount on new LCD but make pins flush with bottom of circuit board (due to new display clearance requirements - LED back light is thicker).
- To power the LED back light, I tapped +11 volt unregulated from the C2 capacitor (K1000 power supply) leads on the power supply (after the 5 amp fuse). DO NOT USE the PURPLE wires used for the EL back light - you will destroy the back light (and perhaps start a fire). The +11 volts are regulated with a 7805 linear regulator (use bypass caps near the terminals) followed by a 1N4004 diode at the output (in series) to drop the voltage down to the 4.2 volts needed by the back light. Watch the polarity of the LED connections and polarity on C2. The regulator gets warm - I added a heat sink and bolted with one of the LCD display mounting screws. Leave the old purple wire connector to the power transformer unconnected - it is not used. Since the primary +5V regulator for the K1000 is rated at 2 amps and the fuse is rated at 5 amps, I figured I could tap this and regulate another 200 mA without overtaxing the PS and blowing any fuses.
-For LCD contrast control: I clipped pin 12 from the LCD header connector and wired a small 10K pot to pins 12 (wiper), 13 (gnd) and 14 (+5V) and attached to the backside of the keypad with glue gun. Alternately, a pot mounted thru a hole drilled in the back of the K1000 would offer external contrast control to the user.

The result: New LCD display with bright LED back light for the K1000!

Parts list:

LCD display from Jameco 365982 (PICVUE PVC160206QYL04)
10 K potentiometer (Bourns)
7805 1 amp voltage regulator
1N4004 regulator diode
10 uF, 25 volt tantalum chip capacitor
1 uF, 10 volt tantalum chip capacitor
New right-angle header connector (or reuse old one)
Hookup wire to make the connections.

Step by step and lots of pictures: (Note: the pictures open in a new window by default so you can put them all up at once if you want. Some browsers will let you right click on the picture link and open in a new tab.)

Remove the old display and disconnect the purple wires. See details in the other display repair pages if you need help removing the old display. Be sure to unplug your keyboard before you start. The power to the old EL (Electro luminescent) back light and will not be needed with the new display. Unsolder the purple wires from the old display EL back light, and unplug the connector from the the circuit board. You may want to save the wire and connector in case you ever want to go back to an EL backlit type display.

Old LCD Display with connector and EL wires still connected

Old LCD side view (Old display is thinner than the new one)

Unplug the old EL power connector

Prepare the new display assembly: Refer to the pictures and the process provided by Michael (above).

-Solder a connector on the new display.  Either remove the connector from the old display and solder it to the new display or solder on a new one.

-Mount the potentiometer to the display board. 10K pot to pins 12 (wiper), 13 (gnd) and 14 (+5V)

Mount and connect the potentiometer

LCD contrast potentiometer

Mount the 5 volt regulator (with its capacitors and diode, heat sink etc)

7805 regulator and components detail

Another view of regulator

Various pictures of the completed display board

Header and contrast pot

Note wires going to power supply connection

Another view

Connect the LED 5 volt regulator to the K1000 Power supply:

Overall view of power connection

Close up of power connection

Mount the new display to the circuit board:

Mounting the display

Completed job

Nice Results

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