JAMMArcade.net – Page 57

Super Pacman PAL 1M update

PAL Updates Comments Off

Dec 012017

From time to time we get a message saying a PAL we have doesn’t work. Usually when this happens there is little we can do as we no longer or never did own the PCB. On this occasion however we found a resolution.
Kyle point out that the file we had for Super Pacman 1M didn’t work for him. He claimed the equations for the PAL didn’t include the use of input pins 5 and 6. To back up his words with a schematic showing then attached.
The strange thing about this is he also dumped the PAL in his programmer and got the same output file as the original dumper (Channelmaniac) did.
From here Kyle built the 27C020 adapter and bruteforced his PAL chip. This time he got something that did work.

His recreation is now available for download in place of the old one.
I have a suspicion the Topmax programmer has a little bug in the handling of PAL10L8 chips although the other dump supplied by Channelmaniac supplied does work without issues so who knows.

Defender repair log #2

PCB Repair Logs Comments Off

Nov 302017

After reparing my Defender ( see this log: https://www.jammarcade.net/defender-repair-log/ ) I noticed that the screen had some horizontal lines of different brightness.

At first I didn’t give much attention but then I decided to look at this issue deeper.

Moving the screen left and right with the monitor commands I noticed these defects:

Having the experience of a similar problem on my Burnin Rubber ( https://www.jammarcade.net/burnin-rubber-repair-log/ ), to me it was clear there was a video blanking problem

With the schematics in hand I found this circuit:

Signals from 7420@5C were good so I started probing the 7400@4B

All signals were good except that pin 10 was floating.

Looking at the above mentioned schematics, pin 10 is tied to the nearby pin 11!

I checked the board and found out that actually the pcb has no trace connected the 2 pins togheter!

No broken traces, it is actually simply not there!

I connected the two pins and…..

Game fixed!

Now I am wondering if my CPU board revision has a production error.

Searching on internet I haven’t found a similar problem therefore I would like to have a feedback from other owners of Defender if their pcbs has the trace or not.

Liquid Kids repair log #2

PCB Repair Logs Comments Off

Nov 302017

Received this Japanese version of Liquid Kids for a repair running on a different F2 hardware.

The game was playing fine but hadn’t any sounds.

Amplifier and preamps were good so I started to probe the sound circuit logic.

The Z80 sound cpu ram had some weak signals

After replacing it , the sound was restored.

Popeye repair log

PCB Repair Logs Comments Off

Nov 302017

Quick repair this one.
Received this board recently from a great eBay seller.

It was sold as faulty and indeed it was. On power up I was greeted with this static screen.

As the Z80 is already socketed on these boards I hooked the Fluke 9010 straight up and did a RAM test. As I was expecting, this failed.

The main RAM is located next to the 4 program ROM’s. One socket and one new RAM chip and we have a nice easy fix.

Punk Shot repair log

PCB Repair Logs Comments Off

Nov 272017

Some days ago I received this faulty Punk Shot PCB (manufactured by Konami in 1990)

Game had small glitches over the sprites and played mute:

MASK ROMs check reported two bad devices:

Usually jailbars mean some problem in data bus so I went to look at relevant circuit.As in many Konami PCBs the sprites generation circuit is condended in two ASICs : the ‘051960’ which generates the address lines for the MASK ROMs and the ‘051937’ which reads data.Indeed I found a missing connection beetween pin 84 of the ‘051937’ and pin 28 of the 8Mbit MASK ROM @K7

This was caused by a broken via on solderside:

Patching it restored graphics, MASK ROMs check successfully performed now:

As for lack of sound I quickly pinpointed the fault in a 2k x 8bit static RAM @E6 (connected to Z80 audio CPU). piggybacking it restored sound.Once removed I had confirm it was really bad :

Job done.

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