There is a hardware bug that may occur on the replica 1 boards. It causes occasional dropped characters from the display. There is a fairly easy fix but it does require soldering.
Requirements: .01uF ceramic disc capacitor, soldering iron (25W preferred) and solder.
Locate the chip labeled 74LS04 on the circuit board. Pin 3 is on the side that is closer to the edge of the board. Pin 14 is on the other side of the chip top pin. So, the pins are labeled as follows:
|(74LS00 is here on the board)
|
|
|74LS04
|
|__8_____7
|__9_____6
|_10_____5
|_11_____4
|_12_____3*
|_13_____2
|*14_____1
|
|----- this is the edge of the board
|
|----------- 6821 is here on the board
|
http://www.applefritter.com/?q=node/view/1666
Pin 1 and 14 are closer to the 6821. Connect the ceramic capacitor on the bottom of the board to pins 3 and 14. Make sure the capacitor doesn't touch any of the other pins on the chip. This will eliminate all dropped characters.
If you have any problems doing this procedure, feel free to email me for help. I will perform this procedure for you for free but I only ask you pay shipping.
I finally went past the local RS and picked up a 0.01uf capacitor today. I couldn't believe I didn't have "nary a one" in the junk box in my workshop. Soldered the cap per the instructions and tested the unit for an hour or so -- no dropped characters!
Thanks Vince, for an easy fix to a minor but annoying problem.
Larry Nelson