PCB Repair Logs – Page 69

Quartet repair log

Mar 042016

Here is a recently repaired Quartet running on Sega pre-system 16 hardware.

quartet1

The 3 replaced chips are highlighted in red. I will explain every step of the repair process below.

1) The game was booting to a garbled screen:

quartet2

The 74LS04 located at 1H (an inverter, manufactured by Fujitsu) had good clock signals on entry pins 11 and 13 but had floating signals on outputs pins 10 and 12. Replacing the chip changed the result on boot…

2) I then got a screen with garbled graphics but with a countdown appearing at the center.

quartet3

This is normal on pre-system 16 games. Normally, after reaching 0, the game is booting. Here, I got a black screen after the countdown.

I noticed that the reset pin on the 68000 had a square looking wave signal, which was pretty weird (it should be a linear signal at +5V). The chip that generates the reset signal is a MB3771 located at 1G (again, manufactured by Fujitsu). Probing its pins made the game sometimes booting. I replaced it by a new 3771 chip and the game was now starting normally.

quartet4

3) The game was working and playing fine except for the FM sound that was inoperative (only the voices could be hear). It was due to the YM3012 located at 1B (a DAC). It had good looking signals on its inputs but nothing seemed to get out of its outputs. After replacing it I got the FM sound back.

Now the game is fully working.

Rainbow Islands repair log #10

PCB Repair Logs 2 Responses »

Feb 252016

Another Rainbow Islands PCB to repair.

This one had issues with the sprites which were broken up and seemed to be repeating, looked very much like a stuck bit on the sprite addressing;

IMG_20160224_112137583

IMG_20160224_112142174

All tiles and background graphics were fine, so I knew it was something to do with the sprite circuit.

The first thing I did was to look at the area where the sprite data is read from the two eproms. The two 74LS244 buffers checked out fine, but one of the 74LS373 Octal Latches had an output pin stuck HI (pin 9);

IMG_20160224_112155598_HDR

So I desoldered it;

IMG_20160224_113645345

I confirmed the Octal Latch was bad in an IC Tester. So I soldered in a socket and replaced with a fresh Octal Latch;

IMG_20160224_114050662

PCB sprites now restored;

ri_pcb_2

ri_pcb_3

Atari Asteroids Deluxe repair log

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Feb 202016

Sometimes lightning does strike twice.

I was recently sent an Asteroids Deluxe PCB which was exhibiting corrupted vectors.

When I got the PCB, I put it on my test rig and was presented with the following in TEST mode;

IMG_20160215_160220667

GAME mode;

IMG_20160215_160158687

The symptoms were pretty much identical to the last Asteroids repair log I posted. Note however this is an Asteroids Deluxe, however it is pretty much identical hardware to Asteroids except that Asteroids Deluxe has a pure digital sound circuit via a Pokey chip (Asteroids is analogue and no Pokey).

I immediately probed the 74LS42 decoder at E6, which had two outputs stuck HI.

IMG_20160215_160124793

So I desoldered it;

IMG_20160215_161027015

Tested it in my IC tester;

IMG_20160215_181037047

Socketed and replaced it with a fresh decoder;

IMG_20160215_161344449

Fire her up again;

IMG_20160215_160348150

Now working, except that the PCB would sometimes crash or refuse to boot. I was able to determine that three of the six ROM sockets were worn. So I replaced all of them for reliability;

IMG_20160215_162641553

IMG_20160215_165025775

IMG_20160215_162807350

Now working 100%.

Poker Ladies repair log #1

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Feb 202016

I recently received some faulty Capcom pre-CPS PCBs.As most of you know, these board are well known to commit suicide.As you can read from the Dead Battey Society site, “the way suicide work is that the batteries on board supply power to a bit of RAM that holds a decryption table. This table is the key to decrypting the encrypted program stored in the board’s ROMs. When the battery dies, this table goes away and the program code can no longer be decrypted. The CPU no longer has valid code to execute. The board stops working”.

In particular Capcom pre-CPS boards all use a single 3.6V battery and a custom Z80 marked “Kabuki”.The Kabuki has the RAM with the decryption table built right into it.

My Poker Ladies PCB committed suicided and all I got was a static blue screen:

Poker_Ladies_suicided

After reviving it with the use of patched ROMs available from the Dead Battery Society site and doing some modification on PCB (thanks to Corrado for providing me info), the board successfully booted but showed sprites issue:

sprites_issues

EPROMs containing this part of graphics were reafd fine so my first suspicions were on the custom sprites generator marked “86S105” (84 pin PLCC package) which addresses the devices :

86S105_sprite_generator

I played the card of its replacement taking a spare from a shorted Block Block PCB:

86S105_removed

and I won since sprites were fully restored:

sprites_restored

Bubble Bobble (bootleg) repair log

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Feb 202016

I never had a Bubble Bobble PCB in my collection so recently I bought this bootleg board (original one is too expensive for my taste) called Super Bobble Bobble :

Bubble_Bobble_bootleg

When I powered it up, at first glance it seemed to play fine except for the lack of sound which I promptly fixed reseating and cleaning the sound CPU ROM.But playing some games I noticed that screen was yellowish :

color_issue