TK-803R 8-Port Rack Mount KVM Switch

Fixed USB issue


I got this switch at auction for a decent price, marked as "as-is untested" and with 8 cables.  Two of the cables were black instead of grey, and longer.  USB wouldn't work on any machine.  Firmware upgrade failed to resolve.  Change to PS/2 and/or different keyboards/mice failed to resolve.  Hooked to another testbed machine with black cable and worked fine.


After further investigation the working cables had ONE difference in pinout that I could find - there was an extra pin for the USB ground at the KVM end of the NON-WORKING cables.  Here's a pic of the USB pinout:

KVM Pinout

Pin 10 was common with 6,7,8 on non-working cables and unused on working cables.  ( Most of the other pins are for actual VGA, I don't know why they chose to use the VGA ground pins for USB rather than other normally available VGA n/c pins)

I simply broke off pin 10 on the "bad" cables and ~magic~ they work now :-)

VGA will work with 1, 2, 3, 5, 6, 7, 8, 10, 13 and 14 ( basically you need 5 signal pairs which are supposed to be their own coaxial sheilds: 1->6 Red, 2->7 Green, 3->8 Blue, 13->5 Hsync, and 14->10 Vsync ) which leaves 4, 9, 11, 12 and 15 available.

Standard VGA Pinout:

  1. VIDEO   Red
  2. VIDEO   Green
  3. VIDEO   Blue
  4. ID2/RES   (normally n/c)
  5. GND   HSync
  6. GND   Red return
  7. GND   Green return
  8. GND   Blue return
  9. KEY/PWR   (normally n/c)
  10. GND   VSync, DDC
  11. ID0/RES   (normally n/c)
  12. ID1/SDA   (normally n/c)
  13. HSync   Horizontal sync
  14. VSync   Vertical sync
  15. ID3/SCL   (normally n/c)