Status: FIXED

Repair cost:  $0.50

KLOV Post:  http://forums.arcade-museum.com/showthread.php?t=156908

Symptom:  Single shot firing doesn’t work.  Holding fire button down for auto-fire does work.

Diagnosis:  Since firing works, button is working.  Logic issue.

Fix:

• 10/30/2010 – Traced fire button back to 74LS157 @ D6 (Aux board).  Replaced chip and single shot firing now works.

Status: FIXED

Repair cost: $2 (questionable if part was really needed)

KLOV Post:  http://forums.arcade-museum.com/showthread.php?t=146427

Symptom:  Game board exhibiting strange display behavior – random vectors scrolling back and forth across screen.  Game plays blind.

Diagnosis:  Problem located on AVG board.

Fix:

• 08/21/2010 – AUX board and cable verified good.  Tested individual boards on a working setup.  Problem is located on AVG board.
• 08/22/2010 – Cleaned and reseated 5 socketed RAMs, the 2 vector ROMs, and the CPU.  Board now has no XY output voltage.
• 08/24/2010 – Tested several chips in the vector generator data shifter section, which confirmed good.  Logic probe pointed to DAC-312 @ D10.  Replaced with no change.
• 10/30/2010 – Began with game in test mode, no display.  Swapped CPU with known working 6502 and got a single blue vector on screen and activity on the slam switch (switches test screens) and long steady beep.  Confirmed activity on CPU pin 37 & 39.  Activity on E2 pin 1 & 2.  Confirmed ROM activity on the CS1 & CS2 lines.  Theory of operation doc said long steady beep in test mode points to bad vector ROMs.  Flip-flopped the ROMs (socketed) and test pattern appeared.  Adjusting X/Y position, linearity and BIP controls brought test pattern into view.  Went out of test mode and game worked.

Notes: DAC replacement could have had an effect, but hard to tell since game was dead – DAC outputs never changed, but inputs upstream were still bad at that point.   However, after the DAC replacement, I never saw the pattern shown in the video again. Original CPU was later confirmed good.  Bad/dirty sockets ended up being the culprit despite cleaning of chip legs and using contact cleaner before they were inserted into their respective sockets.

Status: FIXED

Repair cost: About $50

KLOV Post:  http://forums.arcade-museum.com/showthread.php?t=98417

Symptom:  Monitor dead.  Original 6100, fireworks on deflection board, R100 burned through.

Diagnosis: Low voltage section of deflection board is toast.  Perform cap kit, install LV2000, concentrate on chassis transistors & power transistors on deflection board.

Fix:

• 08/02/2009 – Installed cap kit + extra parts, LV2000.  F100 & F101 blow immediately after powerup.
• 08/18/2009 – Replace diodes, transistors on LV2000.  Replace blown (underrated) D100-103 with 6A2 diodes.  Replace Q603/Q703 on frame.
• 08/24/2009 – Learn, inspect work, double-check, triple check…smoke test tonight.  Deflection board fixed – we have monitor chatter, but only half a picture.
• 09/17/2009 – F600 now blowing on powerup.  Replaced blown Q606.  Powers up and runs for about 5-6 seconds with vertical line before F600 blows again.
• 06/25/2010 – Replaced all frame mounted transistor sockets with new ones.  Monitor now powering up.  Issue with Tempest boardset (link), monitor verified working with another color vector game.

Notes:

The frame-mounted transistor sockets were most likely causing intermittent/bad connections from the corroded and weakened leafs.  The intermittent connections were eventually leading to the transistors shorting out, causing a domino effect of other parts to fail, or a fuse to blow.  Every time a fuse would blow, the proper thing to do would have been to test all the transistors (on the frame and deflection board) for shorts before continuing.  Replacing all 6 sockets eliminated this issue.

Eventually, the culprit parts were the MPSU07/57 power transistors on the deflection board.  These parts are very expensive and/or hard to find, but I bit the bullet and replaced them all, which fixed the problem.