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Heavy Unit repair log #1

Dec 142015

I got a dead Heavy Unit PCB with a white screen on boot:

hvyunit1

Looking at the MAME driver for that game I could see where the program roms were located (5C for the main program rom and 5P for the sub program rom).
I started probing around the CPUs and program roms. The CPUs (2 x Z80) seemed active and the program roms had pulsing signals on most of their pins. A few were inactive and connected to nearby GALs (labeled MD-500 and MD-501). All the I/O pins were stuck low on these two GALs while they had pulsing inputs.

There are 3 GALs in total on that board, MD-500 is connected to the main program rom, MD-501 is connected to the sub program rom and MD-502 is connected to the sound rom.
Surprisingly all these 3 GALs had inactive I/O pins. I got a working Heavy Unit PCB from a friend, compared the signals on the GALs and saw that almost every I/O pins were pulsing on the 3 GALs.

These GALs were not available online so I started desoldering them on both PCBs.
I put sockets on the dead PCB, socketed the GALs from the working board and the game booted ! …but with partially missing graphics (I had colored squares instead of sprites):

hvyunit2

Looking at the PCB I supposed the main program rom at 5C was not original as it had no label. Dumping it revealed it was from a US version. Looking at the MAME driver, I could see that every of the 4 versions dumped in MAME had a different ROM layout and my version was not dumped (the numbers on the labels were not in MAME). Particularly, there was a 512kb ROM at 2F on every versions in MAME that wasn’t soldered on my PCB, although I found its content spread on 4x128kb ROMs at other locations. The main program ROM was probably looking at the wrong location so I soldered a socket at 2F to put the 512kb ROM (from one of the MAME dumped versions and labeled B73_08) and the sprites were back. 🙂

hvyunit3

Here is my PCB with the added 512kb EPROM from MAME at 2F (equivalent to B73_17 + B73_18 + B73_19 + B73_20 on the left):

hvyunit0

ps: I’m still looking for the original program ROM for my PCB (labeled B73_24 and located at 5C) to be dumped so I could remove the 512kb at 2F and use the original 128kb ROMs already present on the board. I suppose it is a japanese version.

ps2: I wanted to dump the GALs from the working board but they were protected. To dump protected GALs I needed to use a method by Charles MacDonald. First, I used this adapter in order to read my GALs as 27C020 EPROMs: https://techno-junk.org/files/adapter-v2.png
Then, I used PD.EXE and WinCUPL to recreate the GALs from my raw dumps: https://dreamjam.co.uk/emuviews/readpal.php
These GALs are now available on https://www.jammarcade.net

Irem and Konami PAL dumps update

PAL Updates Comments Off

Dec 132015

In the past days the user ‘PJW’ sent in a couple of PAL dumps from an original IREM Ninjia Baseball Bat Man PCB.These PALs seems to be specific to this game and are located on the ROM board.Original devices were two PAL16L8 whose dumps have been converted by him into GAL16V8 with PALTOGAL utility and successfully tested on PCB.Thanks to him.

Yesterday I dumped the PALs from an original Konami Aliens PCB.The devices, two PAL16L8, were unsecured so I could read them in a programmer and then convert into GAL16V8.Both dumps have been successfully tested.

Space Invaders (Taito) 3-Layer repair log #1

PCB Repair Logs Comments Off

Dec 102015

I was recently given a Taito 3-Layer Space Invaders boardset by a friend to look over. The problem was that it was not running, completely dead with a clicking sound coming from speaker (sounds like watchdog barking to me).

I powered up the PCB stack on the bench and checked the status of the 8080 CPU. I could see right away from probing pin 19 (SYNC) that the clock circuit was not running.

On the ROM board, I could see that the crystal was intact, so I checked the 74S04 (IC1) which I was sure was drives the clock next to the crystal. I found that most of the pins were floating. Replaced it and I now have a clock (note to myself, 74HC04 will not work), watchdog no longer barking but still no display.

ace_si_1

On further probing, found a bad 74161 counter at location IC6 with pins 11 to 15 stuck HI. Replaced this and I now have a display, but it appears to be doubled up;

ace_si_3

Eventually located the problem to IC28 which is a 74LS83, pins 2, 6 & 9 were stuck LO. Replacing this restored the display;

ace_si_2

Note, I am using the composite input on my Plasma TV, as the PCB is composite only and not RGB.

Space Invaders live to invade another day!

Tatsujin repair log

PCB Repair Logs 4 Responses »

Dec 102015

I have this Tatsujin PCB in my collection :

Tatsujin_PCB

Some days ago I wanted to play it on my Astro City so, before rotating vertically the monitor, I tested the board on a supergun.Game was running absolutely fine but I noticed some wavy lines on screen as it was some kind of interference/noise:

I remembered I had same issue on some boards in the past and fault was due an electrolityc capacitor with increased ESR (the role of a capacitor is to block the DC filtering the AC ).So, with my ESR meter I went to test in-circuit the electrolytic capacitors and I came across a 470uF 16V one @C1 (the one that filters the +12V for the audio amplifier) with a high ESR :

bad_470uF16V@C1

You can see from ESR chart that a typical value for a 470Uf 16V electrolytic capacitor should be 0.2 Ohm while I measured 33 Ohm.So I desoldered and measured it out-of-circuit having confirm it was really bad (53 Ohm measured):

470uF16V@C1_out_or_circuit

With a good capacitor fitted no more wavy lines and finally I could enjoy this cool shoot ’em up on my Astro City.

Jungle King repair log

PCB Repair Logs 1 Response »

Dec 082015

I bought this faulty original Jungle King PCB from a JAMMA+ forums user last year but I never had time to look at :

The game itself is a classic, I remember I was used to play it during my childhood in arcade rooms and on home computer.So, I decided to fix it once and for all.Time to build the needed JAMMA adapter (board use a separate connector for power) and I got this scenario on first boot:

All the sprites were intact but background graphics were all messed up.The RAM test reported no problem :

But, since all the RAMs on CPU and VIDEO board were already socketed, I want to test the chips out of circuit anyway and I found a bad 2016 @IC56 on CPU board:

With a good RAM fitted, the graphics were perfect now but the background music was absent, I could hear only the sound FXs.After some research I found that the CPU board was missing a ROM @IC52:

This ROM is, indeed, responsible of the music and only few games on same Taito SJ hardware have it so probably my board was a conversion from another game which didn’t use it (Elevator Action seem to be the common donor board).Anyway, antoher great classic preserved!

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