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Final Star Force repair log

Jan 062016

Recently got this Final Star Force PCB with graphical glitches on the sprites.

This game uses a motherboard (pictured above) and has a romboard on the other side fitted with no other chips than the game’s ROMs.

All the ROMs were tested ok on my programmer and cleaning the connectors and looking at the signals, everything seemed fine with that romboard.
The motherboard has a rather simple layout with a lot of RAMs, some ASICs and a few TTLs. After a few hours looking for suspicious signals, I finally found the faulty ones.

There is a row of 12 Sanyo LM33464G RAMs (64k-word x 4-bit). Two of them were bad (the ones at IC22 and IC33). Piggybacking them with new ones partially brought back clean sprites, even if there were a few glitches remaining. These glitches totally disappeared after replacing the RAMs.
As these models of RAMs are a bit uncommon, I took compatible TMS4464 as replacement (highlighted in red):

Here are before and after pictures:

Gunbird PAL dump added and Rohga PAL set tested

PAL Updates Comments Off

Jan 052016

In the past days the user ‘NeTaXe’ posted a request on JAMMA+wanted forum, he was looking for the PAL chip marked ‘3021’ @U69 that was missing from his Gunbird PCB.I accepted his appeal and in my turn requested dump of this PAL on Dumping Union MAME mailing list.Some hours later our member Corrado Tomaselli kindly posted it (as well as others from various Psikyo PCBs) so ‘NeTaXe’ could revive his board.Thanks to Corrado for providing the dump and to ‘NeTaXe’ for testing it .

Today I could successfully verified the Rohga – Armor Force untested PAL dumps made from ‘Muddymusic’ some time ago.I actually tested them on a Wolf Fang – Ku-U-Ga 2001 PCB (japanese version of Rohga) confirming dumps works for both versions.

Haunted Castle repair log #3

PCB Repair Logs Comments Off

Jan 052016

Another Haunted Castle repair after the recent one from Corrado.

Board was in good shape :

Haunted_Castle_PCB

But it showed jailbars on sprites, besides the sound was missing :

sprite_issue

So I started to probe the two 4Mbit MASK ROMs containg sprites data and I found a bad signal on pin 28 of the one @J5 (good on the left, bad on the right) :

MASK_ROM@J5_data_line_comparison

I desoldered the MASK ROM and my programmer reported, indeed, troubles on pin 28 while I tried to read it :

768C04@J5_bad

Loading the dump in MAME I could reproduce exactly my issue :

issue_reproduced_MAME

With a programmed 27C400 as replacement of this MASK ROM the sprites were correclty restored so I went to troubleshoot the missing sound.With my analog scope I found weak signals on some data line of the 2018 SRAM @F2 (which the Z80 audio CPU accesses to) :

data_line_2018@F2_comparison

I promptly removed this SRAM which failed when tested in my programmer :

bad_MCM2018@F2

With a good RAM fitted the sound were restored but music was noisy and scratchy :

The FM sound generator is a Yamaha YM3812 @D5 which is connected to an external YM3014 DAC @C4.Probing its digital output (PIN 21) revealed differences compared to the healthy signal from a good board pictured below :

good_serial_data_YM3812@D5

So, I removed the chip and installed a good one :

YM3812@D5_removed

This restored a clear sound.Job done, board 100% fixed!

Contra / Gryzor stereo sound

General, Guides, Technical Info 2 Responses »

Jan 032016

Contra / Gryzor shares almost the same hardware specs with Combat School / Boot Camp, Fast Lane, Flak Attack / MX5000, Haunted Castle / Akumajô Dracula and Trick Trap / Labyrinth Runner.

But among these titles, it is the only game that offers a stereo output thru a 4-pin connector on the board (labeled CN2).

First, you have to select stereo by plugging a connector on CN4 (and put switch 4 of DIPSW3 to off).

contra-sound

The thing is that all the boards I’ve seen still delivers mono sound when you plug this connector (originally brought by Konami and present on the board) on the stereo plug. Why ? Because it doesn’t have the good wiring…

As shown on the picture above, this connector originally comes with pin #1 wired to #2 and pin #3 wired to #4. In that way and plugged on the stereo connector (CN4), it mixes channel 1 and channel 2 from the YM3012 DAC to the LA4445 amp which results a mono output.

To separate the channels, you have to simply modify the connector by wiring pin #1 to #3 and pin #2 to #4.
Now plug it on CN4 and enjoy stereo sound out of CN2. 🙂

There are other Konami games that use the same connector to choose mono or stereo. I’m not sure about the wiring for every game. To my knowledge they are:

– Salamander
– Jackal / Top Gunner
– Devil World / Dark Adventure
– Gradius II / Vulcan Venture
– Ajax
– Lightning Fighters / Trigon (stereo works without modification of the connector)
– Parodius (stereo works without modification of the connector)
– Surprise Attack (that game seems to have a mono sound design, despite the stereo connector present on the board)

ps. If anybody knows if the original wiring on these boards allows to deliver stereo sound or any other board that is using this connector, I would be glad to know and add it here.

Megablast PAL dumps tested

PAL Updates Comments Off

Jan 032016

Today I could test the two PAL dumps we had on database from a Megablast PCB.They were submitted from an unknow source.I added proper chip labels and PCB location too.Actually the PCB has six PLDs but four of them are shared with Liquid Kids which have been already dumped previously by me.

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