Oct 292018

Got another Tumble Pop for a repair, this time with the background totally messed up

The background is stored in one 4Mbit maskrom silkscreened MAP-02

Probing the chip revealed all the data lines were floating.

Decided to desolder it and read it as 27c400. Strangely the programmer didn’t complain about missing continuity on some pins as normally happens

with these maskroms but the read gave only 1F and 00

I put a socket and since I didn’t have a spare 27c400, I programmed a 27c160 (16mbit eprom) and installed it with pin 1 and 42 out of the socket.

In this way the pinouyt exactly matches the 27c400.

With the eprom in place the game was fixed 100%

TumblePop repair log #1

 PCB Repair Logs, Repair Logs  Comments Off on TumblePop repair log #1
Apr 242018

I got this game for a repair:


The game had some background problems ( unfortunately I forgot to take a pic ) and a sprite problem:


The background problem was fixed reflushing the custom chip 56.

As for the sprite problem, after some time checking the part of the circuit responsible for the sprites, I found a couple of 6116 sram @D5 and D6.

One of them had some weak signals on the data lines and tested out of circuit it was confirmed as bad


After replacing the sram the game was fixed

Burnin’ Rubber repair log

 PCB Repair Logs  Comments Off on Burnin’ Rubber repair log
Jun 282017

I bought this game for my collection some months ago.



I tested briefly and it was OK. After a few weeks I decided to make a good play but the game developed a strange problem:





As you can see from the pics above, the screen was very dark and the brightness was not steady.

Also all the objects left trails of different brightness.

The problem was somewhat similar to when you don’t have video GND connected but as you can see

the text HI SCORE was repeated on top and bottom.

Adjusting the horizontal size of the image with the monitor pots ( vertical on the game) I noticed the screen didn’t shrink, it was like it had no borders.

I had immediately remembered that on the CPS1 hardware , on certain screens of some games ( 3 wonders selection screen for example)

the image is very dark and this is due to a flaw in the video circuit of the CPS1 hardware which doesn’t blank properly the video at the edges

leading to some monitor electronics to loose the black reference and behave strangely.

Charles McDonald on his website  https://www.techno-junk.org/ has a fix but right now the link is missing because he is restructuring the page.


Anyway back to the topic, I was convinced that my problem was due to video blanking not working properly, so I downloaded the Bump and Jump

schematics available from Bally (  the japanese ones are impossible to find ) and searched for a video blank signal and tested all the TTLs involved until I found this:


Output pin 5 of 74ls74@1B was floating and didn’t clear the 74LS273 connected to the video DAC


Therefore the video was not blanked properly on the edges.

Changing the TTL@1B  fixed the problem


Unfortunately after a couple of plays,  the pcb developed two other problems:

  1. Car didn’t go left
  2. car crash sound was broken


The first problem was fixed by replacing the 74LS367@4E on the sound board ( directly connected to the left direction pin)

Second problem was fixed by replacing one AY8910.

The game, for the moment, is working nicely 😉

Karate Champ repair log

 PCB Repair Logs, Repair Logs  Comments Off on Karate Champ repair log
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.

Diet Go Go repair log

 PCB Repair Logs, Repair Logs  Comments Off on Diet Go Go repair log
Oct 312016

The game had two problems.

First one was the music that sometimes when switching on the game was glitched (very fast tempo or corrupted voices)

The first problem was fixed by replacing  capacitor C7 which was used to reset the chips and didn’t work correctly.



Second problem was some black pixels on some elements of the background.


After shorting some data lines of the gfx maskroms I found the one responsibile for the background images.

Normally when a markrom fails you get blocky graphics. In this case was only some bad pixels.

Looking on the solder side of the pcb I immediately noticed one pin of one address line of the background image markrom touching the network resistance beside which forced the address line to 1.


Disconnecting it solved the problem