Category: Gorf

Gorf repair log – Space Cadet level indicator issue

Status: FIXED

Repair cost:  42 cents

Symptom:  Space Cadet light doesn’t work.

Diagnosis:  Test bulb/sockets, check level section circuits.


  • 12/2/09 – Swapped bulbs, sockets to test in other rank lights that were working (i.e. Space Captain).  Replaced all bad bulbs that were found, verified all sockets were working.  Light still not working.  Tested caps and transistors, found a bad ceramic cap and one bad transistor.  Replaced bad ceramic cap.  No change.
  • 12/3/09 – Replaced TIP-110 transistor, Space Cadet light now works.

Gorf repair log – Player 2 button stuck closed

Status: FIXED

Repair cost: 6 cents

KLOV Post:

Symptom:  2 coins always starts 2-player game.  Checked diagnostic screen and it showed P2 button always closed.

Diagnosis: Continuity between common ground (orange/red) and P2 button (red/yellow) lines all the way back to the board.  Problem on mainboard.


  • 10/15/09 – P2 button: Pin 19 on J1 connector.   Runs thru R16, R32 which tested good.  Traced P2 line back to U3 (a MC14539B multiplexer IC) pin 10, which was stuck high.
  • 10/19/09 – With the help of a friend, realizing pin 10 on U3 is an input, something upstream must be causing the high signal.  Tested U3 for shorts (conductivity tests between inputs/Vcc), everything tested fine.  A series of pullup resistors and a cap is upstream of that pin….  Pulled resistors, which tested good.  Pulled C16 (104Z ceramic axial cap) which tested bad.  Waiting for parts.
  • 10/24/09 – Replaced C16, P2 no longer closed.

Gorf repair log – no sound


Repair cost:  Approx. $3 (Some parts replaced unnecessarily, should’ve only been $1 fix)

KLOV Post:

Symptom: No sound

Diagnosis: 2A fuse blown on power brick.  Check all fuses, then sound amp circuit.


  • 9/21/09 – Replaced 2A fuse, no change.  Pulled sound amp board and found a Kemet 15uf 20V tantalum cap at C1 shorted & 2 fried resistors at R1 & R4 with flame/smoke marks above them.  Although the resistors tested in spec, I replaced anyway.
  • 9/26/09 – Replaced C1, sound is back, but garbled and staticky.
  • 10/11/09 – Swapped in a buddy’s working amp board, sounds awesome, so it is the amp board for sure.  Replaced TIP31 power transistors on mine, no change.
  • 10/12/09 – Tested voltages, got 16v at all critical locations on board, according to schematic.  Replaced CR1/CR2 with a 1N4007, no change.  The diodes at these points are actually piggybacked with a glass-encapsulated monolithic capacitor.  104Z (.1uf 50v) axial ceramic caps on order.
  • 10/24/09 – Replaced axial ceramic caps piggybacked at CR1/CR2, and volume pots, no change.  Checked R1/R4 again, and realized I replaced with 330 Kohm resistors instead of 330 ohm.  Replaced with appropriate value resistors & sound is back.  A few unnecessarily replaced parts here, but leaving them on because board sounds better than it did before repair!