JAMMArcade.net – Page 30

64th Street – A Detective Story repair log #2

PCB Repair Logs Comments Off

Dec 212018

Got from Portugal this mint 64th Street – A Detective Story PCB, a beat ’em up released by Jaleco in 1991 :

The board simply booted to a static garbage screen:

At a deeper analysis both 68000 CPUs were not resetting properly on power up :

On the main one there was no transition from LOW to HIGH state, /RESET line went staight HIGH :

On the sound CPU both /HALT and /RESET lines were stuck LOW:

I traced back the lines to a typical power-on reset circuit based on the TL7705 voltage monitor IC which I replaced with no luck:

The circuit is made of few other components, specifically there are two 0.1uF mylar capacitors connected to pin 1 (REF) and pin 7 (SENSE)

I got few Ohms when I measured resistance across their terminals (after detached one leg from circuit), they were almost shorted :

I replaced them :

Board successfully booted into game with no further issue :

Repair accomplished.

Out Zone repair log #7

PCB Repair Logs 4 Responses »

Dec 192018

Got from Portugal this Out Zone PCB, actually a low-budget korean version :

At visual inspection the board lacked of two 6116 SRAMs (but sockets were installed)

After fitting them I powered the board up and I got the usual black/white wavy striped screen but no boot into game, 68000 main CPU got stalled right after :

Multiple could be the reasons, in particular this Toplan hardware requires the sound circuit to be running otherwise the whole system can’t be initialized.A Z80A rules the sound system :

When I did piggybacking on it I got a ‘SUB CPU ERROR’ message on screen :

Once removed the IC I had confirm that it was really bad.With a good Z80 the board successfully booted into game but sprites were all blocky (it seems this is a common issue of this hardware…)

Sprites data are stored in four 1Mbit 28 pin MASK ROMs :

Devices were soldered in on my board and not socketed like usual so I was forced to remove all of them for dumping.Two of them gave different CRCs at each reading :

Specifically the ones marked ‘ROM1’ @1B and ‘ROM4’ @1L :

I replaced them with two 32 pin 1Mbit non-JEDEC EPROM devices.All seemed fine but while playing the game I noticed some sprites (like explosions) had lines through :

Looking at hardware I figured out that the sprite line buffer is made of four 6116 (2k x 8-bit) static RAMs:

Probing them with a scope revealed some dead outputs of the one @12L :

On the right no activity on some data lines of 6116 SRAM @12L Good signals on the left for comparison

The chip failed the out-of-circuit testing:

Installing a good RAM chip finished the job.Repair accomplished.

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

Reproductions 1 Response »

Dec 062018

The ‘UEC-01’ and ‘UEC-02’ are two custom ICs you can find on most Seibu/TAD Corporation PCBs also marked as ‘HB-1’ and ‘HB-2’.They are ceramic modules in SIL/SIP package.Here’s how they looks like:

The first handles I/O, the latter drives coin counters/lockouts.Reproducing them was straightforward given the simplicity of their internal circuit so for sake of completeness I took into account also the ‘UEC-02’ although nowadays few people use coin counters:

Testing on a Blood Bros PCB :

The ‘JK-03’ can be found, instead, on Jaleco MegaSystem1 hardware, it accomplishes the same function of the ‘UEC-01/HB-1’ handling the inputs.It comes in form of a SIL/SIP ceramic module as well (with different pin counting and pitch though)

Having no part to analyze I used some available schematics in order to reproduce it:

Due to the lack of a working PCB I could not test it hence volunteers are welcome!

Toki repair log #2

General, PCB Repair Logs 1 Response »

Dec 022018

I have two Toki pcbs in storage, both with sprite errors. I saw a video from lukemorse1 (who actually inspired me to start repairing arcade pcbs) on youtube where he worked on a Toki pcb, also with sprite errors.

Here’s how the error on board #1 looked like:

So there are blocks surrounding the sprites.

From Luke’s video (https://youtu.be/Czdt_yTNRTs) I identified the area responsible for sprite handling and I quickly found a 74LS273 with a stuck output at pin 19:

Checking with the multimeter, I found that this pin was almost shorted to ground:

I quickly desoldered the IC and tested it with my VP-398

Replacing it with a working 74LS273 made the sprites appear as they should:

So a big thanks to lukemorse1 and also as always to caius for always helping out 🙂

CK2605 Logic Diagram

General Comments Off

Nov 262018

While searching through some documents from Data I/O I came across a bunch of logic diagrams for various PLD’s. One of them was for the CK2605.
As I’ve not seen this in the wild before I thought I’d upload it.

*click the picture for PDF

Older Entries Newer Entries