Corrado Tomaselli

No background in electronics. Learned everything by reading pdf books and expecially Video game logic Vol 1 by Atari and in general early Atari and Williams arcade manuals

Esh Aurunmilla pcb repair log

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%

Karate Champ repair log

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Dec 192016

I bought this game for my collection.

I had already Karate Champ player vs player but this one was the rarer first version , japanese revision titled Karate Dou.

The game was very dirty and rusty and despite being declared fully working, the sound was completely missing.

The seller proposed a refund by sending back the pcb.

Before taking this road I decided to give a try at repairing it since the schematics for this pcb are available on jammarcade.net (they are not the same as the more common player vs player!) and the hardware was pretty simple.

After cleaning it in the washer machine, I started the trouble shooting

I immediately noticed that all the 7 sound eproms (BE2o – BE26) and the ram beside them had no activity on the data lines.

So I probed the /CE line and it was stuck high for everything.

That means the devices are in standby mode and they cannot output anything.

With the help of the schematics I traced back the source of the problem to IC18, a 74ls138 who outputs were all stuck high despite the activity on the inputs.

After replacing it, I tested out of circuit and the programmer confirmed it was faulty

By replacing IC18 with a good one, the sound was fully restored.

Note: If you have Karate Champ player vs player which use the same adapter, only remember that the older Karate Champ uses also -5V for the pre amps. If you forget to wire it , you get a very noisy and hissing sound.

Terra Cresta repair log #2

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Dec 192016

I got this faulty pcb in change of some repairs.

The seller told me that the game was bought as working but after some time it developed a problem on the background with some repeated tiles all over the place.

I could confirm the behaviour, but after a couple of troubleshooting sessions the problem became worse and the background was only white.

The game has not schematics, so after some time spent to understand where the background generator was sitting I could isolate the problem on the ram@18D which had some data lines stuck low.

After replacing it, the problem remained but at least the ram had all the datalines working.

With the logic probe I then found a 74ls273@18E which had all the outputs in the grey area.

After replacing it, the background was fully restored

WWF Wrestlefest repair log #2

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Oct 312016

When switching ON the game, sometimes it had very fast tempo music.

It happened 1 one out of 10 but it was very annoying.

So I used my frequency counter when it happened and I noticed that the 3.58mhz quartz ran at about 10.58mhz!

I changed it with a know good one but again it happened very often.

I was sure it was something connected to the quartz oscillator circuit and given that the resistances are difficult to be faulty I decided to change the cap C47 (33pF) with known good one.

After testing about 30 cycles of switching on and off the game didn’t develop again the problem

Game fixed.

wwf