Repair Logs – Page 52 – JAMMArcade.net

Rolling Thunder repair log #2

Feb 042017

While I was playing this game from my collection ,I discovered it was missing all the samples (gun shots, walk and so on).

The game is a Namco system86 with an additional daughter board used for the samples

Before beginning the troubleshooting I searched on Internet for a similar problem and found a repair log

where all the caps on the daughter board weere changed , restoring the samples.

I am not a fan of changing caps randomly so thanks to Atari I checked the schematics and

found that the on the daughterboard there is a little circuit which produce 24V out of the 5V for the op amp.

Around that circuit there was a hissing noise therfore I checked if the 24 volts were present which was confirmed.

I proceeded with my sound probe to see if from the op amp I could hear the samples but when I turned on the game,

it continued to reset itself….the watchdog was active.

At this point I was a little puzzled and tried to disconnect the daughterboard which granted me with the game that booted

but with missing background and crashed as soon as the attract mode began.

I took some customs from various Namco games and checked if the game booted but no luck.

Also I hadn’t another Rolling Thunder to check the two customs on the daughter board therefore I put the pcb apart for sometime.

After some weeks i resumed the pcb and without much hope I checked various TTLs until I found a 74LS244@A1 on the daughterboard

which had pin 12 not oscillating properly while the input was healthy (Fujistu part….)

I piggybacked it with a good one and the game booted briefly correctly.

After changing it, I returned to the original state with the gameplay without samples.

I tested the output of the op amp TL074 with the sound probe and I could hear the samples.

Ttherefore there could only be one cause which was the capacitor @C1 placed between the output and the daughterboard connector, which infact was tested as open with an ESR meter

Changing it restored all the samples.

Lightning Fighters repair log #3

PCB Repair Logs Comments Off

Feb 042017

Received a Lightning Fighters for a repair.Board was in bad shape, some ICs were missing and solderside had a lot of scratches:

In the details, it missed two 4Mbit MASK ROMs used for sprites (but rounded machine-tooled strips were installed in place of them), the YM251 and MB3722 amplifier and its heatsink.Besides, the YM3012 DAC was partially desoldered and damaged:

At power up I was greeted by the typical flashing blank screen, board was constantly resetting due active watchdog circuit:

This meant that main CPU program code couldn’t be properly executed due a probable problem in 68000 busses.With the help of schematics I went to check this circuit and found a missing connection between data line D4 (pin 18) of the program ROM @E15 and corresponding data line (pin 1) of 68000:

Tracing back both pins I found a broken trace on solderside :

I restored the connection and board successfully booted with obviously no sprites and sound due missing components.I decided to fix the graphics for first so I burned two Macronix MX27C4100 EPROMs (same pinout of 27C400) to replace the two missing 4Mbit MASK ROMs @K2 and K8.In this way sprites reappeared but they were glitchy:

MASK ROMs check reported a bad device @K2 (and another one @C5 but this was due the missing YM2151 as I discovered later)

Again I checked connections of the device @K2 against schematics and found intermittent contact between pin 21-31 and VCC (pin 31 of a 27C400 EPROM must tied HIGH to enable the Word-wide organization of data).Who put hands on this board removing the two MASK ROMs and installing round machine-tooled managed to rip off the rivets which are inside the holes, this explains the poor contact of the two pins.I reinforced the connections with some AWG30 wiring them between the solderside of the pins and alternative VCC points :

Sprites were good now but still not perfect, some of them (like explosions) had jailbars:

I reflowed the ‘053244’ custom ASIC sprites generator:

Jailabars were gone:

All graphics were pefect now, confirmed also by the MASK ROMs check:

So only the sound needed to be restored.l fitted all the missing componens (the YM2151 and MB3722 amplifier with its heasink), removed the partially desoldered YM3012 replacing it and at same patched some broken traces on its solderside:

MASK ROMs check reported now success also on the device @C5 (which contains PCM samples)

Once entered in game I had confirm that sound was fully working.Another PCB saved from certain death!

Gemini Wings repair log

PCB Repair Logs, Repair Logs 3 Responses »

Feb 042017

I bought this game for my collection as fully working but unfortunately it had sound problem.

The FM part was very distorted and the drums (which are samples) were missing.

I noticed that someone attempted already to repair the sound section.

There was an LM324 and a potentiometer changed and a flying wire underneath which looked offcourse not done in factory (not pictured)

The game has no schematics and unfortunately, as a protection, Tecmo covered all the traces with a special paint, so it is really difficult to trace the connections.

The game runs on the exactly the same board as Silkworm even if the pcb code code is different.

On Silkworm they put a Z80 with some logic inside an epoxy block just to prevent a romswap

With Silkworm board in hand I could confirm the flying wire was not original, so I proceeded to disconnect it.

The game now had no FM music and only samples!

With my sound probe I proceeded to “listen” to the music which offcourse was being clearly produced from the OP amps but disappeared at one point between the resistors.

The cicruit was very complex and I couldn’t follow up very well without seeing the traces.

A bootleg , which is an exact reproduction of the pcb , could be very useful but I hadn’t any.

After some hours, I noticed that one of the resistor ( R26) was moving a little bit and with a screw driver I could confirm it wasn’t soldered well on the pcb!

Actually there were three of them that weren’t soldered correctly and this was a factory fault because they didn’t fill completely the pad (you can see on the pic the gap without solder ).

After soldering the three resistors the music and samples were restored but still I had this ugly distorted sound!

I was about to desolder the amplifier to change it when I saw something casually that catched my eye.

In comparison to Silkworm pcb, on my Gemini Wings there was an additional capacitor in pos. C18 and it was a different model than the others.

It was added by the previous repairer for unknown reasons.

Often the manufacturers prepare the pcbs to add different models of amplifiers therefore they design additional circuits which are not used.

After desoldering the cap at C18 I fully restored the music output

Esh Aurunmilla pcb repair log

PCB Repair Logs, Repair Logs 1 Response »

Feb 042017

I got several months ago this really rare game from a laserdisc collector for a repair. It seems that this game was made a few units and many of them very found in Italy .

This collector infact has another fully working unit in an original cab but wanted to repair this pcb as spare part, which came from another original cab but in very rusty conditions.

When I received the pcb, many attempts to repair were made, it had a lot of chips already in sockets and jumping wires all around due to the poor soldering skill of the one who attempted the repair.

On top of that, the pcb had some overheating (disconnetion between bottom layer and top layer).

I made a Jamma adapter without any pinout or schematics because this game has no documentation whatsoever.

Luckily the pcb design is really simple, with only TTL logic.

When turned on, the game didn’t even sync with the monitor. Given the fact that the game has only one clock I immediately started my troubleshooting

by looking around that part.

I immediately found out by tracing the circuit that 3x 74LS161 (Fujitsu parts) had lots of output dead.

I procedeed to change all three of them

and finally was greeted with some colours

As you can see, the game still didn’t boot and was stuck

I checked the only program ram on the game (near the battery place) and found out that the data pins were not working.

The strange thing was that the ram was already socketed and was good.

Turned out to be the first of several desasters made by the previous repairer.

He soldered badly the GND pin which apparently was not making contact to the pad, so the ram was not powered.

After fixing the issues, I finally was greeted with this image:

Good news, because it meant the program was running but was not finding the Laserdisc unit

At this point I was quite sure I repaired succesfully the game , so I met the collector at his house and tested the pcb

with the original cab, but the game still didn’t find the laserdisc unit!

Ok, there was something faulty in the serial comunication on the pcb because the cables and laserdisc unit were good since they worked

on the other pcb.

The collector was waiting for a Dexter unit, which is a device which emulates a laserdisc and you can store the movies on a micro SD card.

Therefore we agreed I would wait to have this unit borrowed to continue the trouble shooting.

After 3 months of waiting, the Dexter finally arrived and I resumed the trouble shooting.

Tracing back the signals from the connector of the laserdisc, I came to a couple of 74ls245 and one of them had the enable pin in the grey area.

I followed the trace back to a 74ls365 which was exhanged previously and guessed what? Bad soldering again!

I melted the bubble of soldering and restored the connection

Finally the game booted!

I have no TV with composite input therefore I couldn’t see both digital images and the movie of the game but the attract mode worked and I could play the game blind.

The wrong numbers were due to the missing battery.

Therefore , for the sake of completeness I put a NiMh recharcheable battery and I tested the game again.

Game didn’t boot and was stuck at the blue screen again!

To cut a long story short, there was a problem on the Z80 reset line.

The game randomly started but not always, and the battery made things even worse.

At the end I found out that still the same repairer changed the original RST518A, with a BC54 transistor which held the line always high

I found another replacement IC and fixed the game 100%

Sunset Riders repair log #5

PCB Repair Logs Comments Off

Feb 032017

Found this Sunset Riders PCB in a lot bought from a former arcade operator:

The board worked fine except for the audio, sometimes wrong samples were played and often music was not present too:

The MASK ROM check reported a bad device @1D which is the one containing samples:

Obviously I removed this MASK ROM and dumped it but it turned out to be good.This device is addressed by the near ‘053260’ ASIC which processes its data as well.Tracing connections I could figured out that this custom receives serial data from the YM2151 then mixes them with PCM data and output the whole packet to the YM3012 DAC so it’s something more than a samples player, this would explain why sometimes music was missing too.Before replacing the ‘053260’ ASIC I analyzed it with a logic probe and found its pin 10 totally silent, this had to be connected to pin 16 of two 74LS245 @13F and 14F which allow 8-bit of data exchanging between the ASIC and main 68000 CPU data busses.

A simple jumper wire cured the issue.End of job.

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