Repair Logs – Page 76 – JAMMArcade.net

Rastan repair log #3

Feb 122016

Here is a picture showing a recently repaired Rastan PCB with the replaced chips highlighted in red.

rastan2-5

I will explain every step of the repair process here:

1) When powered up, the game was starting but was constantly rebooting after about 5 seconds. I checked the reset pin on the CPU but it was constantly high so that seemed not related to that. I checked the signals on the 2 CPU RAMs @ IC10 and IC22 (2x TMM2063 – 64kb) but nothing seemed suspicious. Anyway, piggybacking the one @ IC10 made the game not rebooting after 5 seconds but after a longer time. That was sufficient to let me think it may be faulty so I desoldered the RAM and it was tested bad on my programmer. Replacing it by a new one made the game working and not rebooting again and again. Good.

2) Well, the game was now playable but there was no FM sound (so no music at all), only voices were audible. Schematics are available online so I could see that the FM sound is generated by the YM2151 @ IC63 then it goes to an YM3012 DAC @ IC78 then it goes to a TL074 op amp @ IC100 to finally going to the MB3731 amplifier @ IC101. Outputs signals looked healthy at the outputs of the YM2151 and I had correct sound for the voices so the issue should be located before the mix between FM and voices signals, so before the amplifier: more probably within the DAC or the op amp. The TL074 is composed of 4 operational amplifiers:

rastan2-6

I noticed that every of the 4 output signals on the TL074 @ IC100 were looking weird with a negative voltage (between -1 and -2 V). There is another TL074 chip on the board that is related to the voices and every outputs showed a positive signal of approximately 2.5 V. That was suspicious so I desoldered the TL074 @ IC100 and replaced it by a new one and the FM sound was back ! (the signals on every 4 outputs were now showing a positive analogic signal of approximately 2.5 V).

3) and 4) Ok, so then the game was fully playable with perfect sound but there was some graphical glitches on a few items, as seen here in the attract mode:

rastan2-3

I have a previously repaired Rastan PCB that had one of its gfx mask roms replaced by an hacked 27C010 EPROM so, due to the nature of the problem here (glitches on only a few particular items), I suspected one or multiple MASK ROMs to be faulty. I started replacing these ROMs with the ones from my working Rastan PCB and got the gfx working perfectly after replacing B04-07 @ IC14 and B07-08 @ IC27. As noticed in my previous Rastan repair log, the gfx ROMs on this board are 128kb fitted into 28 pins chips. Finding blank chips with these exact specs is hard nowadays so I used 128kb 32 pins 27C010/27C1001 EPROMs as replacement (I could use a 27C1000/27C301 EPROM to make the modification even easier but I didn’t have one remaining then). To fit them on the 28 pins sockets present on the Rastan board, you have to make the following modifications on every EPROM:

If you use a 27C301 or 27C1000 non-JEDEC EPROM (simplest way):

Connect pins #30, 31, 32 together and connect them to pin #1 with a small wire.
Connect pin #2 to pin #16 with a small wire.

If you use a 27C010 or 27C1001 JEDEC EPROM:

Connect pins #30, 31, 32 together and connect them to pin #1 with a small wire.
Gently bend pin #24 so it won’t plug into the socket and connect it to pin #16 with a small wire.
Solder a small wire on pin #2 that you will plug into pin #22 of the socket.

I did these connections on the underside of the chip. Here is how it looks on my 27C010:

rastan2-2

And this is how it looks after the 2 chips plugged in:

rastan2-1

Now the gfx are fully restored, as well as the rest:

rastan2-4

Heavy Unit repair log #2

PCB Repair Logs, Repair Logs Comments Off

Feb 062016

Got this pcb to be repaired from a friend.

The pcb was working perfect excepts that the screen was flickering at 1/2 of the vsync.

As usual I visually inspected the board to find loose legs on smd chips but the only one present was good.

I noticed that the pcb had 4x rams 4164 near the video custom chip which are known to be not very reliable.

I started to probe the rams until I found one which had all the signals very weaks.

After soldering a new one, the problem was fixed!

Heavy Unit

Super World Court repair log

PCB Repair Logs, Repair Logs Comments Off

Jan 312016

Another pcb which was part of the cheap deal.

It was completely dead. Given that it is not an interesting game I was about to use it for spare parts when I asked my friend Caius if he ever repaired a Namco NA-1

He told me he once repaired one with a capacitor connected to the reset circuit of the 68000 which faulty and didn’t produce the reset signal.

I tested mine and to my surprise the reset was stuck low.

I changed the capacitor smd 22uF @C5 with one 1uF which I had available and the game booted.

Unfortunately the sound was completely missing, so I probed with my portable amplifier some smd capacitors which are know to be leaking very easily and I found one which interrupted the sound to the main ampli.

After changing it, the sound was very low with lot of background noise.

To end a long story short, I recapped many small smd caps with new ones and restored full volume.

This is a common problem with Namco NA-1 pcbs

Foto 30-01-16 21 58 07

Mustache Boy repair log

PCB Repair Logs, Repair Logs Comments Off

Jan 312016

I got this pcb togheter with other games all untested as part of a very cheap deal

When I fired it up, I noticed that it worked except sound.

This game has a rare Toshiba sound cpu T5182 which is an embedded z80 with ram and rom inside the same package.

One trick to know if the problem lies in the sound cpu is to coin the game. If it works, than the cpu, which also handles the coin inputs, is fine.

That was the case with my pcb, so given that I could hear noise from the speakers, I troubleshooted the pre amps with my portable amplifier.

There are two op amps, one is a 4558 directly connected to the Ym3016 DAC, and the other is connected to the 4558, which is an LM324.

The latter had all the outputs dead, so exchanging it with a good one restored the sounds.

Foto 30-01-16 09 35 24

Wolf Fang: Kuhga 2001 repair log

PCB Repair Logs 6 Responses »

Jan 282016

Some days ago I had on the bench this Wolf Fang: Kuhga 2001 PCB (known outside Japan as “Rohga – Armor Force”) , a good-looking horizontally scrolling shoot ’em up manufactured by Data East in the 2001 :

Wolf_Fang_PCB

When I powered it up, I was greeted by this screen.

missing_SYNC

It was a clear lack on SYNC signal confirmed also by a measurement with a frequency counter on pin 13 solderside of the JAMMA connector.So, given the absence of schematics, I started to trace back the signal with a multimeter but couldn’t find where it was generated.Visually inspecting the board I found a suspicious crack over a trace :

RSCN1560

My multimeter confirmed the trace was really severed.After patching it, the SYNC signal was restored but there were jailbairs on the sprites:

jailbairs_sprites

Sprites are stored in some 42 pin MASK ROMs :

sprites_MASK_ROMs

I visually inspected the area and found another broken trace on solderside which lead to a data line of these MASK ROMs:

RSCN1570

I promptly patched it with some AWG30 wire:

RSCN1572

and sprites were restored:

sprites_fixed

But after this I realized that sound was missing at all.Diverting the audio signal to an external amplifier, I could hear both music and sounf FXs but there was no output from the TA8205AH amplifier on PCB :

TA8205AH_amplifier

So I decided to remove and replace it but , as for my previous Pitfall II repair, I was wrong, it was good.Looking at its datasheet, I could figured out how its mute circuit was made:

TA8205AH_mute_circuit

Checking the 220uF 16V electrolytic capacitor connected to pin 8 of the amplifier gave me a dead short across the terminals.So I desoldered and test it out of circuit having confirm it was really shorted:

220uF_16V_shorted

Replacing it restored full sound.End of job.

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