PCB Repair Logs – Page 109

Silent Scope repair log

Jul 112011

Bought a Silent Scope PCB recently.
It had the “Hardware Error 11P” fault which is known to be cause by the battery failing in the TimeKeeper RAM.
Since the contents of these RAMs are in MAME I thought id fix one up which was probably a stupid idea as I dont have the setup to actually use it, but at least I know I can fix these now.

To get this thing booted up I modified my ATX power supply that I had previously modded to run my NAOMI setup. The power connection are labelled in the picture.

I had to run the VGA output through a standards converter too, it must be 31kHz. Once it was all fired up I was greeted to the startup procedure which consists of what look like RAM/ROM checks. All these passed but then it just hangs on the fault screen for a bit then resets.

The TimeKeeper RAM is located on the top board of a 3 board stack.

I removed the board and set to work desoldering the old RAM chip. It went smoothly considering it had the signature Konami thin traces and small through holes, the RAM just dropped out.

Thought it best to fit a socket in case of any problems with it in the future.
As this version shows up as v1.20, the RAM dump needed if from set UAB.
I did try reprogramming the original but it didn’t hold the data.
After fitting the new RAM the game booted to the test menu.

After working my way through the menus using the pins on the I/O board I was able to finally fire the game up.

So, I have verified that the sound works, the game boots and the digital inputs are working. I have no reason to believe that the rifle wouldn’t work if connected.

UPDATE (06/07/2015):
If you have an Arduino and fancy testing out my Timekeeper programmer ‘sketch’ then you can download it from the Downloads section.
It worked for me but I make no promises it will work for you. Its a basic proof of concept and could do with being developed.

Robocop repair log #1

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Jun 152011

Bought a Robocop board from the AO forums. Seller says the jump button didn’t work.
Doing a visual inspection revealed a burnt out track just off pin 23 on the edge connector, which is button 2, in this case, the jump button.

I repaired the trace but still no joy with getting the controls back.
Further inspection showed that the custom resistor array had burnt out. This resistor array has some modified characteristics compared a normal array, it passes an input out to a different pin and has a few other differences too. As I don’t have any spares of the custom array I decided to use a standard one pulled from a scrap board.

To make this work I had to short pins 6 and 7 together and 8 and 9 together. These are for button 1 and button 2.
The board is now fully working but ill keep an eye out for an original replacement part to fit.

Rastan repair log #1

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May 022011

Very nearly gave up with this one thinking it was a custom IC fault, glad I never.

Was sold this board as a non worker, the guy said it boots to a white screen and the CPU needed to be looked at.
He was right on both counts.

Before I did anything that CPU needed socketed. Once I had done that I fired the board up again but got the same white screen. I checked the data lines of the CPU and they were dead. I initially tried a known good 68000 CPU but this resulted in the same screen.
There are 6 ROMs next to the CPU which are the program ROMs. I pulled all these and checked them against MAME. The first 3 checked were fine the last 3 were actually from an Operation Wolf board and 2 of those were dead anyway. Burned 3 replacement 27c512 EPROMs and tested again.
This time I got a white screen with some garbage on.
After this I plugged in the Fluke 9010 and ran some ROM and RAM tests. The ROMs passed fine but one of the RAMs had failed. The TMM2063 @ IC10 was shot, I used a D4364 as replacement as its the first one I found compatible on a scrap board.
Board still booted with garbage.

All lines on the CPU had frozen.
Checking the game running in MAME I could see that when you first boot the game the whole screen flashes white for a second then the game boots.
I checked the 3 Interrupt line, IP0, 1 and 2, and found that IPL1 was dead, this came from a nearby PAL @ IC36. The PAL was giving an output so I ran a jumper wire to the CPU and booted again.
This time I got a full white screen with the Hi Score at the top and the game ran but only showing the sprite data.

I checked all the ROMs that hold the background data and they all checked out fine. These are MASKROMs and can be read as either 27c301 or a couple of reads as 27c512 with a small modification.
Following the data route from these ROMs I eventually came to a 74LS157 @ IC72. It had dead pins at #3 and #11. Pin 3 should go straight to +5v and pin 11 should come from address bus A10. Ran a couple of jumpers for these and got something a little different, the screen was still mainly white but I could see text underneath it and the sprite colours were now messed up.

Looking underneath the board I found a discoloured track, when I ran the screwdriver over it, it came away from the board looking a little charred.

Only a short jumper required but it was underneath the palette RAM. I started checking the palette RAM and found pin 16 was dead. I removed this 2018 RAM @ IC73 and it tested faulty, replacing this with a 6116 brought the graphics back fully.

Mortal Kombat repair log

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Apr 292011

Simple repair.
The controls were erratic. Using the input test in the diagnostic menu I could see 3 buttons and the right direction were being activated together.
A visual inspection quickly pinpointed the fault. One of the input resistor banks was partially desoldered and cracked.

Trying to remove the IC myself proved quite a task but removed the two parts and slotted in a 4.7k resistor array from a scrap board. Now the inputs work fine.
Just need to find a sound board for it now.

SEGA ST-V repair log #1

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Apr 282011

First repair from the lot I recently got. Sega STV motherboard with Die Hard game.
When booted up with no game cartridge the board passed all it ROM and RAM tests. With a cartridge inserted the board crashes after the copyright screens. All the cartridge tests also came up as being good.
There is a developers test menu that is accessed by holding the TEST button down on power up of the board, this gives you access to a whole host of extra tests, one of them being a Sub-CPU test. Running this test flagged it up as being BAD and the board locks up.

If I pushed down on IC2 (this is the Sub-CPU, an SH2) the board would pass its test.

This fault seems to be very common on STV motherboards and is easily fixed by reflowing solder on all the pins on the SH2 processors. I did both of them for good measure and the board now passes all its tests and the game boots up.

Not played this game before and its actually quite fun, like a mashup of Virtua Cop, Virtua Fighter and a little bit of Shenmue thrown in for good measure, it would make sense as the STV hardware is based on the Sega Saturn (or vice versa?).

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