Sega System 16 Repairs

[channelmaniac]

Fixed: Shinobi
Symptom: Garbage on screen.

Found and repaired 2 cut/gouged traces and repaired bad hack solder job on the Yamaha DAC and LM324 audio op-amp.

Board was intermittently working and would stop/start working as the board was tapped or flexed. Narrowed it down to the CPU crystal oscillator. If you put pressure down on it the game would boot. Replaced the bad crystal oscillator and installed 2 missing NEC2501 ICs to finish the repair.

[channelmaniac]

Fixed: Shinobi
Symptom: Dead

Replaced 6 broken RFI filters on player 1 inputs. A couple were easy to spot as they were crushed. The others were found with a mulitmeter when running a continuity test.

Burned new unencrypted audio ROM chip from the MAME ROM set and replaced the encrypted sound CPU with a standard Z80B CPU to finish the repair.

[channelmaniac]

Fixed: Golden Axe
Symptom: Garbled/Missing Background Graphics

Swapped out the broken socket on IC21 with spare socket from empty IC23. Reset jumpers S1-S6 for proper ROM types on daughter board. Fixed a bent pin on the custom encrypted CPU to finish the repair.

[channelmaniac]

Game: Shinobi
Symptom: Dead

Game was totally dead. Game had NO custom CPU on it and no activity on the ROMs and the CPU HALT* like was held low, indicating a bus problem.

Checked the chips with the WCF (well calibrated finger) and found every ROM was getting hot and the CPU even hotter. Checked the ROMs in the EPROM programmer and found that all were bad. Burned new EPROMs from the Shinobi3 MAME set for all but the sound ROMs and burned the sound ROMs from the Shinobi2 MAME set. (Shinobi3 had encrypted sound and Shinobi2 had encrypted program ROMs)

Replaced the CPU and the board would then boot but had no sound. Checked the reset line on the Z80B CPU. It checked good. Checked the clock line and found it was missing. Replaced the crystal oscillator and then had a clock signal but not at the CPU. Replaced the 74HC74 clock divider IC and had clock on the Z80B CPU but still no sound.

Replaced the sound RAM to get the sound working and to finish the game.

The only thing I could think of was a power spike or (more likely) someone hooked up power backwards.

[channelmaniac]

Game: Shinobi
Symptom: Garbled graphics

Board took a hit on the corner where the PCB Foot is screwed down through the board. There are several traces that run through that area.

Repaired 2 damaged traces on the bottom of the board and 1 on the top then tested. The traces on the top board in that area carry sound data, the bottom connects to the video subsystem.

There are 8 traces on the top of the board but only the outer most of these was damaged. The rest were OK. However, these are LONG traces that go all the way around the outside of the board and are prone to damage. Here they are from the outside of the board inward - just in case it's needed for later.

E20, Pin 14 to CN4, pin A12
E20, Pin 13 to CN4, pin B12
E20, Pin 18 to CN4, pin A11
E20, Pin 17 to CN4, pin B11
E20, Pin 7 to CN4, pin A10
E20, Pin 8 to CN4, pin B10
E20, Pin 3 to CN4, pin A9
E20, Pin 4 to CN4, pin B9

[channelmaniac]

Model: Golden Axe
Symptom: Graphic corruption

Game had garbled graphics that would get better if the ROMs on the daughterboard were reseated, then come back later. Resoldered IC3 on the bottom of the daughterboard and tested.

[channelmaniac]

Model: Shinobi
Symptom: Dead

Repaired a broken trace on pin 10 of the CPU and tested. Repaired a broken trace to fix a graphics corruption problem. Replaced the dead custom sound CPU with a Z80B and reprogrammed the EPROM at location A7 with suicide-free code to finish the repair. Tested.

[channelmaniac]

Model: Altered Beast
Symptom: No sound

Replaced suicided encrypted CPU with a Z80B and replaced the sound CPU's program ROM. Tested.

[channelmaniac]

Model: Altered Beast
Symptom: No sound

Board had already had the encrypted CPU and Sound Program ROM replaced. The Z80 CPU used to replace the encrypted CPU was bad. Replaced CPU and tested.

[channelmaniac]

Model: Altered Beast
Symptom: Corrupt Sound

Sound was garbled periodically. Recapped the audio section and replaced the audio amp. Still garbled. Noticed the garbled sound was at the same place every time. Replaced the suicide sound processor with a Z80B and installed a new sound program ROM. Tested game.

It appears that these suicide custom CPUs can partially fail and not properly play all sounds.

[channelmaniac]

Model: Altered Beast
Symptom: Dead

Cleaned edge connector. Cleaned corroded pin 1 on the 68K CPU. Tested.