|
|
Pre-show testing resulted in a strong burning smell and a mad scramble to locate Money Money as the source with a now dead monitor and flaming LOPT.
|
A NOS Diemen HR 6020 LOPT was fitted with no issues.
|
On retest the monitor was now working with the new LOPT, but the game PCB failed - there was no picture. The spare game PCB was fitted, and the monitor screen & focus adjusted.
|
The spare Money Money game PCB also subsequently failed. Checking the game PCB power rails didn't indicate any power problems and both game PCBs were set aside for repair :(
|
Starting with the basic signals on IC 4A (Z80) pin 6 found the CPU clock idle high.
Working back, IC 2E (LS367) pin 2 input signal 1Hu was floating. This tracked to
connector CN1 pin 26 through to the video PCB IC 2N (LS368) pin 13 still floating. Input
pin 14 was idle low. Checking the rest of IC 2N found:
|
The game didn't appear to boot, displaying static garbage. Testing with the Arduino ICT found ROM, RAM and interrupt checks all passing. The game booted and ran OK with replacement Z80 CPU and the original Z80 was confirmed bad.
|
After a few hours running on the bench the game PCB developed lines in the sprites and sprite corruption. The graphics hardware on this game comprises two mirrored circuits with each side representing alternating horizontal lines. Comparing IC 7L/7K (2148) with IC 7D/7E found both address and data busses looking very different. IC 7H (LS161) had been replaced in the past. Checking 8H (LS161) found the count output pins 11 to 14 all looking the same as if no counting was occurring. IC 7H outputs showed the expected count/divide. I suspected IC 8H was bad. With a piggyback of a replacement LS161 the sprites were still bad but the scope showed signal contention and the correct count/divide overtone on the output signals. Replacing 8H (LS161) fixed the sprites and the game ran on the bench for the rest of the day without any further issues.
|
During the third pre-show test blue became stuck open. The chassis was removed (again) and tested with a meter on the bench. Using the diode forward voltage test to compare between red, green, and blue circuits detected a difference at TR 27 (BF871) in the blue drive. Removing TR 27 and testing with both back-to-back diode and Hfe checks found both looking OK. The difference between red, green, and blue was still measured even with TR 27 removed and I suspected TR 26 (BC237) was bad. Removing TR 26 and testing out of circuit confirmed it was bad. The two other BC237's in the red and green circuits had already been replaced due to failure. TR 26 was replaced, TR 27 reinstalled and the circuit was rechecked to confirm all three colour circuits measured the same.
|
The fourth pre-show test encountered game PCB failure (again) with no boot. The game PCB was removed and tested on the bench with the Arduino ICT that failed "Bus Check" with "E: _RESET26 Lo39", indicating the CPU reset line was stuck active. Working back, IC 5C (LS02) pin 1 was low. Input pin 2 was pulsing from the watchdog circuit. Input pin 3 was idle high from the watchdog disable jumper link 14-13. IC 5E (LS04) pin 4 output was high and pin 3 input was floating. The input for 5E pin 3 comes from a power-on-reset (POR) circuit comprising transistors Q1 and Q2 with a couple of capacitors. Transistor Q2 (BC327) tested OK out of circuit. Transistor Q1 (BC548) tested bad out of circuit. Replacing it with a compatible BC237 fixed the reset circuit and the game booted and ran OK.
|
Pre-show testing of game PCB #006 found blocky sprites. Swapping out ICs 7E,7D,7K,7L (2148) buried buffer RAM had no effect. Whilst checking IC 7D (2148) pin 1 (A6) the blocky sprites disappeared and the sprites now looked normal. The sprite display wasn't affected by PCB flexing or ribbon cable movement. Several power cycles and hours running on the bench didn't result in the issue reoccurring and the game PCB was declared working pending on reoccurrence.