PCB Repair Logs Shadow Dancer

Shadow Dancer

Shadow Dancer

Manufacturer	Sega
Year	1989
PCB Image	Reserved
Pin Out	Sega System 18

Board 1

Repairer: VectorGlow
Forum Thread: Shadow Dancer PCB Repair

Symptom: Many letters displaying the wrong letter and some background graphics corrupted
Diagnosis: The test mode didn’t have a very comprehensive RAM test so swapped in the ROM board, protected 68000 and IC4 from Moonwalker and ran that. The Memory Test indicated that RAMs at IC33, 34, 35 and 36 were faulty, but in fact the LS374 at IC37 had bad outputs

Layout of RAM IC tests for Moonwalker running on this board:

IC5 IC6
IC16 IC17
IC33 IC34
IC35 IC36
IC41 IC42
IC69 IC70

Written down the above as with the wrong letters being used in some cases it was hard to make out what was being displayed, so also ran the test on Moonwalker itself to determine the layout.

Board 2

Repairer: Womble
Forum Thread: Shadow Dancer PCB Repair

Had Jadflat's Shadow Dancer board on the operating table this arvo. It would boot and run but all the sprites were missing...

...on closer inspection the title screen was missing the game name

...there was a complete lack of Ninja Dog...

..and there were elements of the high score screen that were missing.

Basically all the foreground elements were missing, on a few screens there was some flicking messy areas that was probably the remnants of the foreground.

Jadflat had also noticed the remains of a capacitor labelled C3 on the board...

...this should be a 104K polyester cap so I desoldered the stumps and fitted one from a scrap board. It's probably a smoothing cap, so without it the board would be more susceptible to power supply ripple.

The first thing to do with a board that has some brains of its own is to go into service mode and run the RAM/ROM tests, this gave the board the all clear but it did so extremely quickly, far too quickly for any of the tests to have been anything remotely conclusive. It also didn't test all the RAMs on this board, or if it did it reported them under board locations for a different board configuration.

Shadow Dancers is on a System 18 board and I have a single System 18 board in my collection - Moonwalker, which happens to have a very good RAM/ROM test built in, i.e. it takes ages to test a chip before pronouncing a pass or a fail. So I swapped in the Moonwalker ROM board, the protection chip and fired it up. It had a very similar set of faults, the moonwalking feet were half missing, and in the game the sprites were mostly missing, but some were present but badly corrupted, basically same fault, different game.

Anyway - after the 2-3 minute in-depth Moonwalker ROM/RAM test it gave the following output...

...all was good except the RAM chip at IC16, one of the chips not tested by the Shadow Warrior test routine.

On the scope the data pin output looked rather too regular, as if all pins were giving the same output all the time, so I desoldered IC16 and its partner IC17, both Sony CXK5814 chips, the one at IC17 tested ok in my EPROM reader, but IC16 failed.

Fitted a couple of machined pin sockets and refitted IC17 along with a TMM2018 borrowed from one of my boards as I couldn't find a fast enough 6116/2018 on any of my scrap boards.

I tried a couple of chips of unknown speed but they resulted in flickering sprites, the original chip was a 45 nano second so it needs to be the same or faster.

Powered her up again and ...

..Ninja Dog is back..

.. the title screen behaves correctly..

..all sprites are restored...

.. and the missing elements of the high score table are filled in.

I did think the lines through the purple backdrop on this screen was a second fault, looks very similar to an effect you get if one of the ROMs has a bad data pin, but this screen is the same in MAME.

So - D16 and D17 on system 18 boards are almost certainly the foreground graphics RAMs, so no working RAM chip = no foreground.

Board fixed

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