Sunset Riders repair log #3

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Mar 162016
 

Got this Sunset Riders PCB from my friend Joachim:

Sunset_Riders_PCB

He told me PCB suddenly stopped working while he was playing at it.When I powered it up I got this :

Board was constantly resetting sign that the watchdog circuit was active.The main 68000 CPU was halted and its data/address bus in high impedance state.For first I disabled the watchdog by closing the jumper ‘JP’ near the JAMMA connector:

J_jumper

The /RESET signal was correctly generated by pin 10 of the custom SIL ‘051550’ but its clock input on pin1 was stuck high :

051550

This signal labeled ‘AFR’ is generated by pin11 of a 74LS138 @13G:

74LS138@13G

74LS138@13G_PIN15

Obviously, since the CPU was halted, I got no activity on inputs and outputs of this 74LS138 but I found that its pin 15 (an output) was almost shorted to ground (only 6.3 Ohm of resistance):

74LS138@13G_PIN15

This was clearly abnormal, two were the possible causes : either this output was shorted internally to ground, either something was tiying it externally.I removed the 74LS138 but it was good and pad of pin 15 was still almost shorted to ground.Part of schematics posted above shows pin 15 connected to pin 1 and 15 of some 74LS253 multiplexers.Using again my multimeter in continuity check I could find the point of less resistance in the area of the two 74LS253 @14B and 13B:

74LS253_13B_14B

I couldn’t know which was exactly the bad one so I desoldered both and tested out-of-circuit.The one @14B failed:

74LS253@14B_failed

Fitted a good IC and the board lived again.

fixed

 Posted by at 11:37 pm

Haunted Castle repair log #4

 PCB Repair Logs  2 Responses »
Mar 162016
 

Another Haunted Castle repair log.

Actually it was the japanese revision called ‘Akumajou Dracula’.The board was in clean condition:

Akumajou_Dracula_PCBt

But this was the scenario after I powered it up:

issue

Vertical lines across the screen and missing sprites were the most noticeable issue.As usual I started my troubleshooting with a visual inspection focusing in the tiles and sprites generation circuit and I promptly noticed this:

DRAM_H3_H4_backwardsm

Someone (for sure not a great expert…) previously attempted a repair and replaced the two ZIP M5M4464L DRAMs @H3-H4 but mounted them backwards.After correctly installed a pair of new chips I got this improvement:

improvement

There were still jailbairs across some sprites.From my experience in past repairs I knew this kind of issue are caused by the other couple of ZIP DRAMs @L20-L21 (where the ‘007121’ custom @J16 accesses to)

DRAM@L20_L21

I replaced them and sprites were fully restored.I was declaring the board as fixed but I noticed that some layers (more than the colors) were missing on some backgrounds like title screen :

layer_issue

With the help of schematics I went to check all the parts of circuit that could be involved until I notice that the input pin 14 of a 74LS399 @D16 was stuck low while all other were correctly toggling:

stuck_data_74LS399@D16

If I shorted this pin with the adiacent one (13), all the layers came back although some colors were wrong:

partially_restored

The signal labeled on schematics’GA1C02′ is generated by the custom tilemap generator ‘007121’ @J16:

GA1C02_007121

So this lead me to play the card of replacing this ‘beast’ in PGA package of 208 pin:

007121@J16

Armed with a heat gun, I removed it :

007121_removed

and transplanted a good know working one taken from a Combat School donor PCB:

007121_donor

And I was right since since this fixed completely the board:

fixed

End of job.

 Posted by at 8:24 pm

PAL dumps update

 PAL Updates  Comments Off on PAL dumps update
Mar 162016
 

Today we have some new PAL dumps.

In the past days ‘coolmod’ posted on Dumping Union list dumps of PALs from a Ray Force (single layer PCB version) ,they were obtained from two PALCE (and tested on same devices) and a PAL16L8 (then  converted and tested in GAL16V8 format).

Joachim Puster sent me dump from a The End PCB.Device was a PAL14H4, I converted it to GAL16V8 and he succesfullly tested it on board.He sent also dumps from a Gunlock PCB (ROM board PCB version), they are in native PAL format (two PAL16L8 and one PAL20V8H).

Thanks to both for these contributions.

As for me, I dumped the two PALs from a bootleg of Legend of Hero Tonma.

 Posted by at 9:11 am

Teenage Mutant Ninja Turtles – Turtles in Time repair log #2

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Mar 122016
 

Easy job: the game soon after POST coined up immediately.

Ran the I/O test and the coin button didn’t work (but it showed a 0 instead of 1).

Testing pin 16 of Jamma connector (coin input) showed that it was stuck low all the time.

Tracing back with the multimeter I found out that the responsible for coin inputs was a 74ls257 TTL @19C which I replaced.

That fixed the problem.

 

TMNT

Superman repair log #2

 PCB Repair Logs, Repair Logs  Comments Off on Superman repair log #2
Mar 122016
 

Game booted and could be played but all the screen was full of garbage and flashing.

I found one of the two rams circled in red that was really hot. Data signals were weak so I decided the replace it.

I could now see some parts of the background, so I decided to replace also the other ram and the game this time was fully restored.

 

Superman

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