JAMMArcade.net – Page 29

Guardians / Denjinmakai II repair log

PCB Repair Logs Comments Off

Jan 142019

Received today from Germany this Guardians PCB, also known as Denjinmakai II, a horizontally-scrolling beat-em-up released by Banpresto in 1995)

According to the owner the game played totally ‘bind’.I could confirm it as soon as I powered the board up :

Board playing ‘blind’

But, as you can see from above video, I was able to restore some graphics by pressing down this surface mounted custom ASIC (QFP 208 pins)

Judging from the heatsink on its top this custom ASIC acts as a GPU generating most of the graphics and video signals too.At a closer inspection I found many lifted pins on all four sides.An example :

I promptly reflowed the IC, this gave me a steady picture but all the graphics were scrambled and, judging from the blueish screen, the RED color was missing too :

Looking at solder side of the PCB I noticed a long and quite deep scratch passing across some traces:

Inspecting the area with a microscope and doing a continuity check with my multimeter confirmed that some traces were severed and other caused unstable contact:

I patched and reinforced the traces with some AWG30 wire :

This lead to few improvements, graphics were still scrambled so I moved on to troubleshoot the lack of RED color.This was pretty easy to fix as the board had a quite clear damage that broke the trace which carries the signal to JAMMA edge connector :

As for bad graphics, I decided to double-check the previously reflowed custom ASIC and found a solder bridge shorting two pins:

Removing it fixed the issue and board completely.Repair accomplished.

Robocop repair log #4

General Comments Off

Jan 112019

I recently aquired a few Robocop PCBs, and this particular one seemed to be working fine at first glance. Eventually however, I realised that certain sounds seemed to be missing from the attract mode.

In particular I noticed Robocops speech as he rolls off the Prime Directives was not there. A closer look playing the game revealed further sounds missing, like the groans from the enemies as you kill them and others.

I then realised that is was just the ADPCM samples that were missing.

So I looked at the CPU board where most of the final digital and analogue circuits are. First I checked the DACs and found no samples present, so went further back to the large YM2203 sound chip. I probed pin 19 of the IC and would have expected to hear the samples here, however I heard nothing except static.

I was able to determine that the ADPCM samples are stored in the EN02 ROM, so I popped this into an eprom reader and checked the content.

The eprom was corrupted, so I burned a new one and the samples were restored.

Another Robocop saved.

BINman program update

General Comments Off

Jan 022019

Today I’ve uploaded the latest version of my BINman software.
This version is v4.3.2 and has had some rewrites and a few extra features added.
First is the ability to deinterleave the bytes of a file into nibbles.
Second feature added can be found under the “Special” menu. It was added as a request from a user. This swaps the nibble values from one byte and the adjacent byte then deinterleaves that file. For example an original file of: “12 34 AB CD” will output two files, one containing “13 AC”, the other “24 BD”.
Its not something I’ve ever had the need for but obviously someone wanted it so here it is.

As usual it can be found in the “Downloads/PC Software” section.

Jaleco ‘JK-03’ reproduction successfully tested

General Comments Off

Dec 312018

Some time ago I made a reproduction of the Jaleco ‘JK-03’ custom SIL used for inputs handling on some Mega System 1 PCBs but at that time I was not able to test it due to the lack of a proper PCB hence I asked for some volunteers.You can read the post here:

Seibu ‘UEC-01’ – ‘UEC-02’ and Jaleco ‘JK-03’ reproduction

Today I can report the reproduction is fully working thanks to the test carried out from the user ‘Astro X’ of AP forums on his Saint Dragon PCB with missing ‘JK-03’ (actually an hack was installed as workaround) :

Thanks again to him for the feedback.

Spelunker repair log

General Comments Off

Dec 302018

I received for repair a quite rare original Spelunker PCB (on Irem M62 hardware).Board is a three stack one made of a top board (which carries most of sound hardware) :

A middle CPU board (specific for each M62 game) :

And a bottom VIDEO board :

The PCB had severe GFX faults, the sprites were only lines vertically stretched all over the screen:

All the sprites circuit lies on bottom VIDEO board which is the same for all games that run on M62 hardware.Looking at Kung-Fu Master schematics I could figure out that data bits from sprite ROMs are fed into the custom marked ‘KNA6034201’ :

The inputs were all active but most of outputs floating:

So the custom was most likely internally faulty.Luckily I have done a reproduction of this component some time ago.You can think of it like a 24-bit parallel to serial shift register:

R-Type repair log and Irem ‘KNA6034201’ reproduction

I removed the custom and installed the reproduction:

The sprites were back but not perfectly as they were lacking of lines and misplaced too:

The sprite line buffer consists in two 2k x 8-bit static RAMs (Toshiba TMM2018 used here) :

Probing them revealed on both a floating address line (pin 1, A7) :

Address lines are generated by the surface mounted custom ‘KNA6074601’ :

Its pinout/implementation from Kung-Fu Master schematics :

I had no other choice than replacing this part so I asked the owner to look for a donor board.He found and sent me a Vigilante PCB which carried the ‘KNA6074601’ on bottom board :

I removed the faulty one and soldered the spare back :

This restored the correct sprites:

Board 100% fixed.Job done.

Older Entries Newer Entries