Thunder Force Repair Logs
Repairer: Paul Swan
BOARD NO: 0015
GAME: Thunder Force
MANUFACTURER: Sega
DATE: 1990
HARNESS: JAMMA
SYMPTOM (06/04/96)
Player one UP didn't work and player two UP was always active. Some other controls didn't work either. Sticky label written by the previous owner said "IC1 faulty".
SOLUTION
The signal was definately getting from the joystick to the board. Tracing the signal path with a continuity tester from the edge connector, through the filter capacitors and diodes up to IC1 confirmed the label. IC1 is a 100-pin SEGA PQFP SMT device and inspection revealed that this was some form of input multiplexor. Some scrap Crack Down boards had the same device, and one of these was selected as a donor. Without the correct facilities, some improvisation was called for. The major difficulty was going to be removing the donor device in tact. In the end I used a diamond PCB cutting saw to cut out a square section on PCB containg the donor device. This small board was then cut very carefully under the donor device from corner to coner (diagonal X cut), thus physically separating each of the four pin faces. Using a hot air soldering iron on each of the four pin faces dropped the four bits of remaining PCB from the pins. The faulty device was removed by lifting each pin off in turn with a fine soldering iron. The donor device was placed on the board and the four corner pins tacked down to secure it whilst the pins were soldered with a fine soldering iron and a microscope. Amazingly, despite the abuse suffered by the donor device and the game board (including what must be the most poorly fitted SMT device ever to grace a PCB), it actually worked(!).
(I doubt whether I would ever attempt something like this again without the correct facilities).