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

Ninja Spirit repair log

 Repair Logs  Comments Off on Ninja Spirit repair log
Oct 262019
 

I have a ninja spirit on my collection since more than 10 years. I play it regularly but the other day it once powered up the foreground layer had some vertical black bars crossing the screen for the complete height on the right side.

After a while also the left part started to blick glitching ( cannot be seen on the screenshot below unfortunately)

The board is an irem M72 and the background and foreground layers are handled on the bottom board. The circuit for both playfields is completely the same.

Schematics are available for Rtype which is the same hardware minus the C board.

I checked immediately the circuit which draws the foreground and decided to check a couple of TTL

With some luck I immediately found one 74ls283@10A (IC 78) which was glitching badly the left part of the screen  when testing with the probe on pin 10.

74LS86@7B ( IC50)was also glitching the screen when testing with the probe on pin 6

The HP logic comparator gave me bad outputs on some pins of these TTLs.

After desoldering them I tested on my TTL tester and they were declared good!

I decided to solder back  new ones to be on the safe side and to my surprise the game was fixed.

Turns out that the TTL tester didn’t catch the subtle faults of these ICs ( not Fujitsu parts!)

SSV system colours problem repair log

 PCB Repair Logs, Repair Logs  Comments Off on SSV system colours problem repair log
Aug 142019
 

Some months bought for my collection Vasara and Vasara 2 in bundle from an american guy.

From the beginning Inoticed that Vasara had very dimmed colours and required to adjust monitor constrast to the maximum in comparison to Vasara 2.

Since I was not familiar with this system I thought it was due to the motherboard revision which is earlier on Vasara ( and there is a factory mod to make it compatible)

After some months I decided to check on internet if someone had a similar problem and I found mentioned on system11 blog about Cave CV1000 colour problems.

Repair – Cave CV1000 colour problems

According to him it’s a very common problems on SSV games and I found also mentioned on japanese blog sites afterward.

I checked with the oscilloscope the signals coming out from the 4 2sc1674 transistors ( RGB ans SYNC) and indeed all of them very about 2volts, same intensity of the inputs.

Signals in Vasara 2 in comparison were about 3,5V

I decided to change all of them and indeed it fixed the dimmed colours which are now very bright and crisp

 

 

What I find really curious is that all of them went faulty, I think  probably the transistors choosen by Seta are not correct for this kind of load.

Maybe someone with a good electronic background can shed a light

Pacmania repair log #3

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Aug 132019
 

Got another Pacmania faulty.

This time the sprites were glitchy with some black lines

 

Custom 39 is usually involved in sprites generation but after testing with a good one problem remained.

There are two 74ls377 connected to it and one @A3 has one missing output.

Changing it fixed the board

 

 

Popeye repair log #2

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Aug 132019
 

Received this board from a friend which booted to a static screen

 

Decided to have a look immediately to the 2k work ram which was a Toshiba which is normally prone to faults.

Changed with an Hitachi 2k

And game 100% fixed with no other errors

Vanguard Centuri Sync mod

 General  Comments Off on Vanguard Centuri Sync mod
Apr 302019
 

A friend of mine sent me a couple of Vanguard pcbs which didn’t sync at all on all monitors I tested.

The only difference I saw was that his pcbs were Centuri versions while my pcb which synced good was SNK version.

Centuri versions on the video board have a factory mod with some flying wires which are not documented on the schematics and which are related to the sync circuit.

 

SNK version has no flying wires on the video board:

offcourse undoing the factory mod on the century board fixes the sync problem but I wanted to learn something more.

It seems that Centuri versions were modified to use the positive sync monitor supplied in their cabinets and probably they also improved the sync

signal in comparison to the original circuit.

Anyway , if you want to keep the mod but invert the sync for common monitors or TVs, you have only to solder the wire which goes to pin 3 of the 74LS05 marked in red

to pin 4.