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The diodes in the keyboard/mouse circuit, D2-5, are ideally very low
forward drop diodes. 1. Schottky diodes (0.2v) would be ideal. 2. Germanium diodes (0.4v) would be a second choice. 3. Silicon diodes (0.7v) are borderline. Experience will tell if switching silicon diodes (e.g., 1N4148) are okay. Hasn't this circuit been used elsewhere for keyboard input? A wired-OR circuit with open collector components would not so critically depend on the diode's forward saturation voltage drop. --John On 07/14/2011 03:11 PM, Sergey wrote: U38 74LS93 was replaced with U71 74LS393 I think that D2,D3,D4,D5 are just generic 1N4148 diodes (unless I missed some conversation that says otherwise). But otherwise your list looks correct to me. Thanks, Sergey On Jul 14, 12:43 pm, nbreeden <nb...@live.com> wrote:I am working on an updated BOM for the 2511 rev of the PCB, to achieve this I took the HC3BOM.TXT file from the original board and using the N8-2511-parts.lst file updated it. Can someone please verify these observations before I post it: U38 (74LS93) was removed D2,D3,D4,D5 - these are Germanium or Schottky (1N270 or 1N5280) R32 was changed to 240 Ohms R33 was changed to 390 ohms R42,R43 were added as 2.2K Ohms P24,P25 (Conn_5, SIL-5) were removed P45 was changed from SIL-2 to SIL-4 P46 was added (Bornier4 Connector) P42 is spare DIP-8 P23 is sapre DIP-16 There are no other spares U8 changed from 74LS07 to 74LS06 P41 was replaced with U62 (14 Pin 16.0MHz Osc) P14 was removed (2MHz Osc) -Neil |