PCB Repair Logs – Page 83

Edward Randy repair log

Sep 042015

I got an Edward Randy with a black screen (but partial sound).

After a few checks with my scope, I quickly found a PAL @ location N5 with no signals on all of its outputs (BUT signals on its inputs).

As PALs from this game are not available yet online, I looked for other games that possibly shared the same hardware/system in order to try using a similar PAL.

And yes, that system is listed as “Data East Caveman Ninja Hardware” in MAME and some of these games got their PALs dumped. It was the case of Caveman Ninja and Robocop 2 that shares an almost identical PCB layout than Edward Randy (there are only a few differences in the GFX ROMs part).

So I burned the PAL at location N5 from Robocop 2 and plugged it on my Ed Randy board and here is what I got:

Well, at that time I was thinking it was due to an incompatibility between Robocop 2 and Edward Randy PALs and I temporarily gave up, waiting to get a dump from a working Edward Randy to be sure…

Then Shoestring confirmed me Caveman Ninja and Robocop 2 PALs @ N5 were strictly identical. It leaded him to believe that perhaps they are all common to each other and maybe there is a different problem with my board, which pushed me to have a look back at my board for possible other faulty chips. And he did well…

I started looking for other issues on the PCB and noticed that bending the board made the garbled graphics changing, even making them better looking at some point.
So I suspected the two SMC Data East customs labeled “55” having bad solder joints and reflowed the solder on them.

It then went way better. I had clean backgrounds in game, full intro with clean texts and pictures, title and Data East logo appearing (didn’t have all of that before) but no sprites in game. I noticed a square on the bottom-right corner that seemed containing garbled parts of sprites.

I then managed to find where the sprites part was located on the board and found two 6116 RAMs @ locations N9 and M9 that had suspicious signals on their data lines (pulsing but weakly and at low voltage). Piggybacking a known good working compatible RAM made parts of garbled sprites randomly appearing on screen.

I then desoldered one of the two RAMs (at location N9). With no big surprise it was tested bad on my programmer. I soldered a socket and put a new RAM in place. There was still no sprites but the garbled square on the bottom-right corner was not there anymore. Data lines on the new RAM were looking pretty much better though with strong pulses at 5V. The RAM located at M9 still showed weak outputs so I replaced it with another good known RAM:

Then sprites magically appeared !

Only one thing was remaining: the voice generating chips (2x OKI M6295) were missing so I replaced them and got the sound fully working.

I played the game several times since that and it is working perfectly.

Lethal Enforcers 2 repair log

PCB Repair Logs, Repair Logs Comments Off

Sep 032015

Got this board as fully working

I immediately noticed some problems on the sprites

Transparent objects and shadows were solid and some sprites had glitches

Konami maskroms are known to be unreliable so I ran immediately the maskrom test reveling that rom @25g was faulty.

Before desoldering I checked also the custom underneath which sometims has pins lifted but it was good.

Upon a close inspection I saw some rust on 3 pins of the maskrom @25g which in my opinion could be the reason of the fault

Therefore I decided to desolder it and resolder a 27c160 programmed with the correct file

Board 100% fixed

Real Break – Billiard Accademy repair log

PCB Repair Logs, Repair Logs Comments Off

Aug 302015

Bought this board as fully working for 30 euros but turned out it had a problem on the audio.

All the music and sound effects were totally disturbed and garbled.

The TA8201AK amplifier was becoming so hot that you could smell it burning.

The pcb has a lot of smd capacitors that are reknown to be unreliable but I noticed that two of them were already changed with normal ones.

I was sure that it was the amplifier shorted internally because in some occasions my 2A fuse was blown so I bought from ebay a cheap one for 4 euros.

On the left side the original one dated 1997, on the right the one bought on ebay, dated 1991 😉

After soldering the new one, the problem remained.

This time I decided to go for more professional approach and downloaded the datasheet and checked all the caps and resistances according to the sample circuit.

To make a long story short, the two tiny caps (C28 and C29, one for the sound sfx and one for the music) connected to the input of the amp were somewhat faulty and leaking under the body.

After desoldering both of them , I noticed they were1nF each and not compliant to the suggested one of the datasheet which should be 4,7uF.

I decided to install only one cap of 4,7uF and shorted the resistances R55 and R74 to mix the sounds before the cap.

This solved completely the issues and got very clean sound with the amplifier running with a reasonable temperature.

Rastan repair log #2

PCB Repair Logs, Repair Logs 1 Response »

Aug 302015

I bought a dead Rastan PCB for a fair price on a forum.

All I got was a screen with garbled graphics on boot:

Luckily, schematics are available online for this board. Anyway, I spent hours with my scope trying to find why there was no activity at all in the CPU area. I desoldered the two RAMs and the 68000 (all were tested OK as well as the ROMs).

Next, I desoldered the 2 PALs that are involved in the address decoding (labeled B04-09 @ IC11 and B04-10 @ IC12) in order to check them and finally discovered that B04-10 was slightly cracked (it is the one at the bottom-left corner of the board, you could figure it was heavily bended there) and, with no surprise, it couldn’t be read on my programmer. See the crack in the middle of the chip, it was unnoticeable before removal:

Fortunately, PALs for this game are available on JAMMArcade.net so I took a blank GAL and burned the equivalent file but then got a black screen… Ok, that was my fault as the file was an untested dump from a PAL16L8 and needed to be converted to GAL16V8 in order to work properly. I did the conversion with PALTOGAL.EXE, reburned it then the game booted !

Great… But my enthusiasm quickly stopped as I noticed some issues:

1) The game sometimes crashed then rebooted, it happened 1/3 times when I started a game.

2) There was no sound (I could sometimes randomly hear a voice looping then fading away).

3) A few sprites were garbled.

It turned out that both issues 1) and 2) were related to a defective sound RAM chip @ IC50.

System11 reports the exact same problem on one of his Rastan repair logs (corrupted sound with main CPU crashing randomly due to a defective sound RAM).

This was not easy to troubleshoot because that RAM @ IC50 had seemingly “normal” pulsing signals on every pins and piggybacking didn’t worked at first. After reading that repair log from System11, I tried again piggybacking and that time it worked ! (well, it partially worked and not all the time)
So I’ve replaced the chip and got it working fine with sound and no freezes !

Only the issue 3) was remaining. The fault was most probably due to one of the gfx mask ROMs @ IC28 (1Mbit into a 28pins chip) that was replaced by an hacked 27C010 1Mbit 32pins EPROM. I could see things changing when touching a couple of pins on the EPROM. Here is a picture of it:

I could replace this bad looking hacked EPROM with a blank TC531000, LH531000 or a HN62331 mask ROM as they seems to have the exact same specs and size than the original mask ROM but it seems nearly impossible to find these chips nowadays.

After comparing the pinouts between 1Mbit 32pins EPROM and 1Mbit 28pins MASK ROM I found what was missing on that hack: pin #2 (A16) of the EPROM was not going anywhere and it should be connected to pin #22 on the socket. I soldered a thin wire on the EPROM and plugged it underneath the chip on the socket.

Plugged back the chip and the gfx were then fully fixed ! (as an example, this axe on the bottom-right corner was garbled before):

Alright, BUT… After playing the game for a few minutes, I noticed when dying that Rastan’s voice was suddenly cut and looped 3 times along with his jumping voice. If I had to replace what I heard with words that would make: DYING/cut/JUMPING/DYING/cut/JUMPING/DYING/cut.
Well, that sounded weird so a verification in the emulator confirmed that was not normal.

The test mode features a sound test so I compared all the voices between my board and the game in MAME and there was 3 voices replaced by this looping sound of Rastan’s dying/jumping.

Alright, had to look back at the schematics…

This was (most probably) related to the voice generating part which is pretty small fortunately as it involves only a few TTLs as well as the Z80, one EPROM and one M5205 (ADPCM sound generator).
Sound ROMs were tested OK and every address and data lines looked fine.

Checking the related TTLs with the scope, I noticed there was no pulsing signals on every of the 5 outputs of the 74LS193 @ IC60 while its inputs were pulsing. This chip is a counter and it is partially doing the link between the sound data bus and the voice address bus. There is another 74LS193 @ IC77 doing the same work for other address/data lines and outputs were pulsing when I pushed the button to generate one of Rastan’s voice in the sound test.

Piggybacking the chip at IC60 made the voices working fine with no weird loop. Also the other voices in the sound test were back. Replaced the chip and finally have now a perfectly working Rastan. (well, played it a few hours and it runs perfectly !)

Thanks to Porchy and Caius for their help on the PAL and hacked EPROM.

Super Contra repair log #2

PCB Repair Logs, Repair Logs 2 Responses »

Aug 292015

A friend asked me if I could take a look at his dead Super Contra PCB which was a 2 boards version (the same game exist in a single board version where all the small mask ROMs on the sub board are replaced by bigger mask ROMs on the main board).

All I got was a black screen with no sound. Checking with a scope around the CPU area revealed there was almost no activity. The CPU is a Konami custom 052001, hard to troubleshoot as I couldn’t find its pinout online.

While checking for possible loose connections on some chips. I found that bending a bit this small chip near the JAMMA connector (an electromagnetic interference filter) was booting the game:

It was a bit loose. I desoldered it and found one of its legs broken. This was hidden behind one of these two small black ferrites. I repaired the leg and resoldered it.

Well, the game was now booting but graphics were a bit messy:

scontra4

ROMs containing graphics and voices are located on the sub board.

I started checking this part as it has a pretty simple layout (basically mask ROMs with buffers) and noticed 3 mask ROMs with corrupted signals on their data lines. These 3 ROMs were all connected on the same bus to pins 2 to 9 (A bus) of a 74LS245 buffer @ location D1:

There are several other 74LS245 chips connected to other mask ROMs on the board and they all seemed to have “normal” activity signals. The B bus of the suspected chip (pins 11 to 18) seemed inactive and was connected to a custom chip on the main board.

I first tried piggybacking that 74LS245 @ D1 but nothing happened. The lines were still looking the same with garbage signal on bus A side, which could be caused by the possibly faulty chip itself. I desoldered it and it was tested bad on my IC programmer. I put a new one in place and the problem was resolved:

Here is what every signal on the A bus (pins 2 to 9) of the 74LS245 chip looked like with the faulty chip (left) then with a new chip in place (right). You can clearly see how bad the signal looked like on the left:

Older Entries Newer Entries