JAMMArcade.net – Page 56

Pac-Mania ROM board repair log

Dec 072017

Received from USA this Pac-Mania ROM board (Namco System 1 hardware) for repair :

According to the owner board played fine but mute, this was confirmed once powered it up.Using my audio probe I could hear sound on the input (pin 2) of the two LA4460 amplifiers but nothing on outputs:

At closer inspection one of them was literally blown up:

So I proceeded to remove both:

and installed two new spares and some thermal compound on heatsink:

Sound restored and board 100% fixed.End of job.

Update:

After converting this board to Splatterhouse I found that voices and other sound FXs were missing:

I quickly pinpointed the fault in a bad TL084 OP-AMP, replacing it cured the issue:

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.