Pang repair log #2

 PCB Repair Logs, Repair Logs  Comments Off on Pang repair log #2
Jun 162015
 

Got a friends Pang PCB here for repair.
He had carried out the ROM swap (made by ArcadeHacker) to desuicide it but he had no output although we could hear it playing blind.
The board is very clean and a visual check revealed nothing.
On powering the board up I got this screen
IMAG1355

I could also hear the board did play blind so that’s a good sign.
I like to make little schematics for boards when I’m working on them and they don’t have any available and I quickly came up with this.
pang

I started probing back from the RED pin on the JAMMA edge connector and soon came to a RAM chip at location 8C. Probing this chip and its counterpart gave me some odd looking signals which I got suspicious about.
These chips are CXK5814 SRAM chips and they seem the be the most unreliable RAM by comparison.
One of the RAM’s had all its data lines stuck LOW while the other chips data lines were all dead despite all the enable lines working as they should and the address lines active.
At this point I was certain they were dead but one last test was to ‘piggyback’ a known good RAM chip on top of the suspected bad one. I chose the one with the dead data lines to avoid potential contention and I got a partial image on screen.

I desoldered both the RAM chips and replaced them. I didnt have any spares in my RAM bin but found a couple of skinny 6116 RAM’s on a scrap bootleg board.
IMAG1353
IMAG1359

Fitting these I now got this wonderful sight.
IMAG1356

IMAG1358

Job done.

Major Title repair log

 PCB Repair Logs, Repair Logs  Comments Off on Major Title repair log
Jun 072015
 

Many of you may think that repairing arcade boards is a difficult task but sometimes it’s not so (well, few times though…).Here is an example.

Got an IREM Major Title PCB (M82 hardware) from my friend Corrado (who is part of JAMMArcade team as contributor):

Major_Tilte_PCB

When I powered it up I was greeted from this rolling screen:

no_SYNC_

There was no SYNC at all.I traced this signal back to a 74LS32 @IC14 on video board but, after checked its logic, it seemed good.I noticed there were some socketed ICs both on CPU and video board.Two of them were TBP24S10 PROMs manifactured byTexas Instruments (you can read its specifications in our “datasheet” section).When I pulled of the socket the one @IC47 I got this:

TBP24S10@IC47

PIN16 (VCC) was broken so IC was not powered at all.A little bit of “reconstructive surgery” on this (other adiacent wobbly ones) pin was enough to restore the correct video syncronism (later I found that outputs of this PROM were connected to a couple of custom ICs involved in video timing generation).

fixed

 

 Posted by at 10:02 pm

Kid no Hore Hore Daisakusen repair log

 PCB Repair Logs, Repair Logs  Comments Off on Kid no Hore Hore Daisakusen repair log
Jun 062015
 

My friend ‘robotype’ sent me some boards for repair.Among them there was this a “Kid no Hore Hore Daisakusen” PCB (キッドのホレホレ大作戦? lit. Dig Dig Kid’s Epic Battle), a pretty obscure (for me, at least) game manifactured by Nichibutsu in the 1987 (released in the Western market as “Booby Kids”):

Kid no Hore Hore Daisakusen_PCB

Board uses, surprisingly for its age, JAMMA pinout so I could power it up without the need of building an adapter as I first thought.Here is all I got, some static garbage:

static_garbage_no_boot

This is clear sign that the CPU is not running so for first  I probed the 68000 main processor.Starting my checking from pin 1 all was stuck LOW or HIGH until I came to CLOCK (PIN15), this was completely silent.I traced it back to a typical clock circuit made of an inverter 74LS04 and a 74LS74 as divider.These ICs were good but when I went further back till to the 16MHz quartz I got this on my scope:

clock_troubleshooting

It was completely dead!Replacing it brought PCB to life again.

PCB_fixed

 Posted by at 5:38 pm

Xevious (Namco PCB revision) repair log

 PCB Repair Logs, Repair Logs  Comments Off on Xevious (Namco PCB revision) repair log
Jun 012015
 

Who of us has not played at least once Xevious?

Xevious is a vertical scrolling shooter arcade game that was released by Namco in December 1982.It runs on Namco Galaga hardware. In North America, the game was manufactured and distributed by Atari.

I had on my bench the Namco version:

Xevious_PCB_800

Board booted correctly, game was fully playable but sprites were missing some lines and also playfiled got some issues:

GFX_issues_

All GFX customs (the sprite positioner ’12XX’, the object RAM addresser ’04XX’ and the GFX data shifter and mixer ’11XX’) were OK since I swapped them with ones of my Galaga/Gaplus boards.Luckily Namco released schematics for this board so for first I checked the part of circuit involved.All was good until I come across this section:

object_circuit

As you can see there are six 74LS161 counters that take DATA from one 2128 SRAM @2S (addressed by the custom “04XX”):

object_RAM

Three 74LS161 address two of the four 2149 RAMs @5M and 5N:

2149

When I went to probe the two 2149 RAM @5N and 5M I found four address lines (PIN3-6) stuck LOW.As I said before, these are addressed by a counter @5S so I went to use my HP10529A logic comparator on it.All led corrisponding to outputs turned ON while all inputs were correctly working.Desoldered and tested it out-of-circuit confirmed it was bad:

74LS161@5S_testing

Fitted a good 74LS161 restored correct graphics.

good_GFX_

 

With this repair we conclude the May season of logs.See you hopefully next one!

 

 Posted by at 9:16 am

Gundhara repair log #1

 PCB Repair Logs, Repair Logs  Comments Off on Gundhara repair log #1
May 302015
 

Got this mint Gundhara PCB, a vertical shooter similar to Ikari Warriors, manifactured  by Banpresto in 1995:

Gundhara_PCB_800

When I powered it up game was fully playable but tilemaps were totally wrong :

wrong_tilemaps

Before you start every troubleshooting, first thing to do is studying the hardware.MAME is a great help for every repairer with its invaluable source of information provided.In this case here is an overview of the hardware (thanks to driver developer Luca Elia):

  • CPU : 68000 + [65C02] (only in the earlier games)
    Custom : X1-001A X1-002A (SDIP64) Sprites
    X1-001
    X1-002
    X1-003
    X1-004 (SDIP52) Inputs
    X1-005 X0-005
    X1-006 X0-006
    X1-007 (SDIP42) Video DAC
    X1-010 (QFP80) Sound: 16 Bit PCM
    X1-011 X1-012 (QFP100) Tilemaps
    X1-014 Sprites?

This information pointed me in the right direction, the part of circuit to be analysed was this:

X1-011_X1-012_800

You can see on the right part of the above picture the two custom ASIC tilemaps generator marked ‘X1-012’ (QFP100 package).When I checked the one @U45 I found some lifted pins:

X1-012@U45_800

A simple reflow of these pins was enough to restore tilemaps:

good_tilemaps

I was declaring this board 100% fixed but while testing it I noticed something wrong in its sound, some PCM samples were played wrongly (like enemy shots) compared to good reference of MAME.Once again our beloved emulator source gave me an help to pinpoint this trouble.There is another custom ASIC which is a 16 bit PCM chip marked ‘X1-010’ (QFP80 package) in the sound circuitry @U57:

X1-010@U57_800

One pin was lifted, a reflow restored correct sound.

Thanks MAME!This repair log is dedicated to you! 🙂

 Posted by at 8:10 pm