JAMMArcade.net – Page 111

Pang repair log #4

Apr 042016

9 years ago I got a Pang for my personal collection. It was still with original battery and I carefully changed it with a new one because I didn’t like the wire wrap mod to desuicide it.

Unfortunately 1 year ago while testing the kabuki desuicider the game didn’t boot anymore, steady blue screen.

After testing succesfully the kabuki desuicider on another board it was clear my Pang developed a problem.

For more than a year I never managed to repair it until I got a Fluke 9010A which showed a problem on the z80 bus, the READ signal was not driveable.

I immeditely noticed that it had a very low resistance to gnd.

Near the Z80 there is a resistor network 4,7kohm. the read signal was connected to a pin of this network which had only a resistance of 427ohm.

pang

I decided to desolder it and install a new one but the game didn’t boot.

I decided to let the game rest for some more time until one day I discovered that the game sometime booted , sometimes not but when it booted it crashed soon after.

Upon closer inspection I discovered that I soldered very loosy a pin of the network resistance!

After resoldering it better , the game booted without problems!

Ghosts ‘n Goblins (bootleg) repair log

PCB Repair Logs, Repair Logs Comments Off

Apr 042016

Got this bootleg board for a repair.

The game could be played with music and sound but had a problem on the text layer:

gng2

gng3

I started probing around until by shorting carefully pins of some TTLs I found the circuit of the text layer on the upper board.

A 74LS86@5J had all its output in the grey area (2.2V):

gng1

Changing it with a new one solved completely the issue:

gng4

gng5

We had two separate files for M92-b-2l.
One was just labelled for M92 hardware and the other was for Ninja Baseball Batman.
I deleted the entry for M92 as the Ninja Baseball Batman dump was from an actual unlocked PAL chip.

End user will not notice any difference, this update is to keep a record of what has been done and when.

Reading Irem MASKROM’s

General, Technical Info Comments Off

Apr 022016

I got an M92 PCB here that uses MASKROM’s from SHARP.
These MASK’s in particular are pin compatible for either 27C020, 27C040 or 27C080 EPROM’s.
It is possible to determine which to dump these as from the markings on the chip. They all begin with the ID LH53#, where # is the identifier of the size.
“LH532” = 27C020 dump
020

“LH534” = 27C040 dump
040

“LH538” = 27C080 dump
080

The remaining letters/numbers of the markings are unique to the game and location on the PCB.

Zaxxon / Future Spy flip screen hack

Guides, Mods 2 Responses »

Mar 292016

Sometimes it is very annoying when you have placed your arcade monitor vertically and certain games are shown upside down and even worse they have no option to flip the screen.

It happens very often with older games but sometimes even with newer games from the 90s.

In these cases you have 2 options: reverse phisically your monitor or reverse the yoke on the pcb of the monitor (not very safe).

Now I show you a new option available only when the games were also prepared for cocktail tables (that means they have already the circuit to flip the screen for the second player)

In this first “flip screen” hack I will take Zaxxon / Future Spy hardware as an example

Future Spy_2

These games have no flip screen option but they have the preparation for cocktail tables play.

The board is very big but luckily schematics are available and they are very clear to understand.

The hack is very simple: input nr.4 of 74ls367@U64 is normally LOW for first player game and HI for second player game.

We have only to force pin 4 to HI (+5V) using a wire so that the screen is always flipped as it was playing the second player even in upright mode.

Zaxxo_flip screen hack

Very simple and effective!

Older Entries Newer Entries