Corrado Tomaselli

Mar 162017
 

I bought this game for my collection declared perfectly working.

Flashgal runs on the very same pcb of other two games developed by Kyugo which are 99 Last War and Legend.

On the bottom pcb it is silkscreened CVG-48C which is very similar to the codes used by ORCA on their hardware

 

Anyway  it seems that in these days I am very unlucky because the game once fired up had a sync problem

 

Tracing back from the SYNC pin I came to a 74LS08@2P

With the frequency counter I got very unstable readings so I proceeded to piggyback it with a good 74LS08 which restored the sync.

After changing it, it tested good out of circuit, yet with the new TTL in place I got a stable sync….

The screen looked very reddish so there was obiviously a palette problem

I checked the palette rams and they were all good so I dumped the colour proms until I found the RED component one @1J which didn’t match anything in MAME.

The prom is an 82s129 and it is almost impossible to find an empty replacement these days.

Therefore I went again for the Bprom to Gal replacement already used last year in another repair log:

Mad Gear repair log AKA reproduction of a bprom to GAL

Since the prom was the very same type I replaced for Mad Gear, I converted the prom file to the PLD equations using Elgen tool U2pa and I reused the same pin configurations which fits nicely without any major hardware mod except a jumper wire to connect GND to the correct pin on the GAL

I tested the the game but I noticed something strange:

The colours were right but there were glitches on the left and right borders and also a flickering red component across all the screen (which cannot be seen on the static image offcourse)

At first I thought it was an access time problem with my GAL , therefore I burned the fastest one I had  but no luck.

I tested directly the signals of the PROMS and  found out that the CE pins were not tight to GND but were controlled by another ttl.

Soon it became clear why it didn’t work: the GAL was sending datas out of sync  therefore producing artifacts.

Since I am not a programmer I asked to Elgen and Caius (who asked to Porchy) an advice how to replicate on the PLD  a tristate behaviour.

All of them were very kind and in few minutes they informed me how tristate works on PLD equations

I added the needed modifications to my PLD equations by declaring each data pin  enabled when pins CE1 and CE2 were low.

 

This completely fixed the colours on the pcb with no artifacts:

 

Again a big thanks to Elgen from http://elgensrepairs.blogspot.it/ for the invaluable tool  and to Caius and Porchy for being always very helful

 

Senjyo repair log

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Mar 162017
 

I bought this game declared 100% working for my collection but as soon as I fired it up I noticed something strange:

 

One of the mountain layer looked very strange and there was also some stripes of mountains in the sky

This game has no schematics and it is a particular complex and populated hardware with lots of TTLS and rams.

The game is on a 3 layers pcb so I had to find a way to test the components in a confortable way:

 

The upper board with the connector has the cpu and sound section, therefore I started to test the bottom pcbs and by shorting some signals I finally found the circuit dedicated to the last parallax layer which is near eproms 19 and 20.

All the signals looked good but the 2114 srams has some dead signals coming to 4 addresses.

Tracing back I found a Texas instruments TTL  74ls157@9C   whose outputs were all totally dead

Changing it fixed completely the background layer:

 

Return Of The Invaders repair log

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Feb 182017
 

Recently I got hold of this favourite game of mine after a long searching. Apparently it is not so common nowadays, so when I saw a sales thread of this pcb  in faulty conditions from an italian arcade forum I took immediately the opportunity and bought it.

The seller posted a video in which the sprites where wrong and the red and blue components were inverted (this latter problem was caused by wrong wiring of jamma adapter)

When the pcb arrived it was in very good conditions with all rams socketed in factory, therefore I immediately tested them out of circuit which unfortunately  were all good (so no easy repair 🙂 )

It had also an horrible hack on the sound amplifier, more on that later.

Therefore I started the troubleshooting without having any schematics and no similar hardware to look for.

Game had this main fault:

and even if it was not seen in the video of the seller, sometimes I got also the logo and some other images messed up

 

The sprite problem I was sure was caused by some wrong addressing of the sprite graphics, therefore I shorted some address line of the eproms on the video board to see which ones contained the sprite graphics and found the four responsible.

Addr 7 and 8 of the eproms 10 to 13 were fixed low. I traced back to a 74ls153@IC38  which had both outputs fixed .

Piggybacking it with a good one restored the sprites, therefore I proceeded with replacing it and fixed the sprite problem

The TTL was from Fairchild (not Fujitsu part!) and it was the oldest one on the pcb, dated 1979!

Now the logo problem, it was strange because sometimes it was shown right, sometimes bad.

After some hours of playing, the logo was not shown right anymore, therefore I asked David Haywood (Haze of Mame fame) where it was contained and it pointed me in the eproms A14 and A15 (different bitplanes which were combined to form the final pic). Both eproms had to be addressed in the same time.

Also he told me that the graphic was bank switched, therefore some logic had to select a particular part of the memory area to show the correct gfx.

I probed their address lines and found the upper one A12, was always fixed low. I forced it high during gameplay and the backdround got corrupted but when the title was shown , the logo was there clear.

So the logo was contained on the upped half of the eproms and the logic was not selecting the A12 bit high or low depending on the situation.

I traced back to the only Fujitsu ttl present on the board, a 74LS259@IC72,  8 bit addressable latch.

Before desoldering it, I tried to understand the datasheet of the part, which is not very common to see on arcade boards , and probes 3 select inputs which were oscillating and the enable line was pulsing everytime it changed from title logo to gameplay.

All his outputs were stuck low, and the HP logic comparator confirmed some outputs were at the wrong logic. Only few are used by the hardware, but I expect in later levels I could get other wrong graphics…

I desoldered it and tested out of circuit:

Turned out Fujitsu was again the source of problems!

I had a hard time to find a replacement, because as said the 74259 is very seldom used by arcade hardware.

At least I found one in the following junk pcbs I had: Rock and Rope boot, Equites and Dig Dug.

I took the one from the bootleg (it is always a pity to cannibalize an original board 🙂 ) and problem was fixed!

 

Since the pcb would go directly in my collection,  the last thing I wanted to fix, was the ugly hack they did by replacing the original amplifier with an LM380 (same used on 1978 space invaders….)

 

This thing worked but it was really ugly!

After spending one hour to clean the disaster with soldering irom and soldering wick, I installed back in place the 2x missing caps and I looked to find the original MB3731 amp among some of mine junk pcbs.

Besides being used on Taito hardware of the era, it was often used on Konami hardware from late 80s/early 90s.

I took it from a junk Main Events pcb and now it looks much better:

 

Sega System16 repair log

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Feb 092017
 

My Alien Syndrome pcb one day decided to stop working and it showed a black screen.

I changed the battery 9 years ago and I thought it was suicided.

Just to be sure I tested it romboard and FD1094 module on another motherboard and it worked without problems.

I took a Tetris romboard then and tested on Alien Syndrome motherboard and this time the game showed a stuck reddish diagnostic screen which unfortunately I didn’t take a picture of.

Tested the inputs to see if there was a shorted one but there were all OK.

The program was running otherwise I wouldn’t get a stuck diagnostic screen therefore looking at the schematics I started to probe the 74LS253 (all Fujitsu parts) to see if the comunication with the cpu good.

The logic probe didn’t show stuck signals but I didn’t trust it and proceeded with piggybacking all of them with a good 253.

The game booted when I piggybacked the 74ls253@C15 but with wrong colours.

I desoldered it and tested it on my programmer and it was confirmed bad

After changing it I was welcomed with a running game but as said wrong colours

I ran the diagnostic memory test and the ram @J10 was given as bad.

Unluckily the ram was under the romboard therefore difficult to test in circuit

I decided to have another look at the schematics:

As you can see we have 2x 74ls244 which address both rams. The RAM given as bad was only J10 therefore it couldn’t be the 244.

After the 16 bits data lines we have 2x 74ls245 , and the first 8 bits from ram J10 are connected to the 74ls245 @H10.

Without even probing anything it was clear for me which chip to change blind

We had a Toshiba 2015 ram and a Fujitsu 74ls245.

Obiviously I decided to change the fujistu part

The guess was right because the game was fixed 100%

 

Shinobi repair log

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Feb 092017
 

This pcb from my collection developed lately a sound problem only with the jump sound which is a sample

 

This particular sample was distorted, the others were all OK

The clock and the 7759 sound chip which is responsible for the samples I was sure they were OK otherwise

all the samples would have the issues

I dumped the sound program rom 11372 and the samples roms 11288 and 11289 expecting that one of them could be corrupted

but surprisingly everything was fine.

If you have noticed, I still the original NEC module with a suicide battery from 1987. The battery is still working after all these years but unfortunately cannot be changed since the module is one piece injected with epoxy.

I started to think that the module could have the decryption key stored in ram somewhat corrupted after all these years and this could affect of course the sounds

Therefore I proceeded to use a z80 with the decrypted program rom taken from a mame set which use the same 5358 rom board (it is currently set 5)

The jump sound was correct with decrypted rom, confirming my theory that the key in the module is corrupted.