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 :

Z80A audio CPU

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 :

Sprite 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 :

Faulty 1Mbit 28 pin MASK ROMs

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.

 Posted by at 9:17 pm

  4 Responses to “Out Zone repair log #7”

  1. Nice fix Caius, those Goldstar Z80’s seem to be a common point of failure. What exact EPROMs did you use to replace the two MASKs?

    I was under the impression that all the MASKs would need to be replaced due to a change in the strapping of the new EPROMs?

    I may have my wires crossed here though.

  2. I replaced the two bad MASK ROMs with 27C1000 from ST manufacturer, the board is already prepared to receive them, no need to set jumpers, etc…you can use also 27C301 from Hitachi as well other compatible non-JEDEC 32 pin ones, refer to this post for a complete list:

    Anyway, I designed a small adapter to use 1Mbit TSOP Flash ROMs as 28 pin MASK ROM but I didn’t yet the find the time to put all together.Here’s how it looks:

  3. Nice repair! What are the components that differ from Japan version of pcb? I suppose that Goldstat Z80 are one of those differences

    • For ‘korean’ I mean the poor manufacturing of the PCB (don’t know if actually is has been manufactured in Korea…).You can recognize it from the components choice, most of ICs are from Goldstar which is not a reliable brand IMHO.Then you can see the coin counters/lockouts circutry has been not populated to save costs.