PCB Repair Logs – Page 81

Raiga – Strato Fighter repair log

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Sep 302015

I got on the bench this Raiga – Strato Fighter PCB for a repair:

Game is a horizontal side-scrolling space shooter developed by Tecmo in 1991.Two were the issues I got when I powered it up.Sound was completely missing ( I got only some samples played randomly) and there were missing vertical lines all over the screen like a sort of scanlines effect:

All video related circuitry is located on he bottom board.Since involved EPROMs and RAMs were socketed I could test them out-of-circuit and they were fine.Then I noticed some dynamic RAMs in form of 12 Sharp LH2464 (64K*4bit) chips.I went to probe them with my oscilloscope and I found weak signals on two data lines of a couple of them (good signal on left, bad on right of the below picture):

So, I removed the two chip and tested into my EPROM programmer where they both failed:

With two good DRAMs fitted, the graphics were completely restored:

So I went to troubleshoot the lack of sound.Main CPU of the audio digital section is a Z80 which commands two YM2203 FM sound synthesis chips for the music and one OKI 6295 for the voice samples.Probing the Z80 revealed random activity/pulsing on all its pins.Besides, chip was wery hot to the touch so I decided to replace it.This was the right move.Board 100% fixed.

Jigoku Meguri (Bonze Adventure) repair log #2

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Sep 282015

My friend ‘robotype’ sent me some boards for a repair.I hope this log will the first of a long row! 🙂

Let’s start with this Jigoku Meguri (the Japanese version of Bonze Adventure) :

all

Board played fine but was silent, no audio at all.Digital part of circuit was fine, Z80 CPU was active and healthy so the fault had to be in the analog section.Main amplifer was good producing some noise when I put my fingers on its pins.Other component involved in analog section were a YM3016 DAC , a couple of TL074 and a uPC4556 OP-AMPs:

As usual I went to probe the analog output (pin 13) of the YM3016 DAC and sound was present although scratchy and distorted:

So I decided to replaced this DAC :

In this way the sound from it was fine:

but board was obviously still silent.Following the path of the signal I came to the near uPC4556 OP-AMP.Sound was still present on its inputs not nothing came out from outputs.I replaced it with a compatible LM358 and this restored sound.End of job.

The Simpsons repair log #1

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Sep 282015

Got this The Simpson original Konami PCB from my friend ‘supermik’ for a repair:

He told me board didn’t boot showing an error on initial self-test, indeed I got this:

Check reported a bad IC @12 (screen upside down was due this fault) which is, in particular, a ER5911 EEPROM used to store game settings (you can find datasheet in our section):

I encountered this fault several times and the only option is to replace the IC (probing it confirmed that the only data output was stuck).So I took this EEPROM from a dead board and, after installed it, I performed the initialization procedure that is to hold down the test button while powering on the board and keep it pushed until a message will confirm the successful outcome :

Bart Simpson, eat my shorts! 🙂

Street Fighter II CE repair log

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Sep 282015

I picked up an original Street Fighter II CE PCB off eBay with minor video issues. The seller also claimed that the sound didn’t work but this turned out to be the volume pot turned all the way down.

Screen was full of jail bars and graphics corruption. Tested all mask roms and confirmed two bad ones ( s92-1M & s92-2M ). These chips appeared to have some liquid spilled on them ( coffee or some other warm drink ) at some point. Several pins on both mask roms were corroded badly. I replaced the bad mask roms & burned the correct data on two EPROMS ( 27c400s ). This cleared up the jail bars however graphics corruption was still present, see the following screen shots below.

After two or three minutes of playing corruption almost completely disappeared. The problem could only be reproduced by turning the unit off for a few minutes and back on again. I replaced three mask rom IC sockets which were also damaged from exposure to the moisture but there was no change in symptoms, this left me scratching my head.

I flexed the B board between at the mask rom area using some pressure from my index finger and the graphics came up better than before as I applied pressure. I knew I was dealing with a break somewhere on the component side of the PCB underneath the sockets. I put the game in test mode & probed the each pin on the mask roms. Eventually I reached pin 31 ( ByteVPP ) on s92-2M, as my probe made contact to it, the sprites transitioned/flickered between looking correct & then glitchy.

I turned the game off & set my DMM to continuity mode. I measured nothing between s92-1M & s92-2M on pin 31, an obvious break here. I patched the break with some AWG wire & hooked it up on the solder side. This fixed the video issue somewhat but I also detected another break on the solder side between s92-1M & s92-3M ( on pin 10 ) which I patched as well. This fixed the game and my graphics came back 100% complete.

Splatterhouse repair log #3

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Sep 262015

Another great game on the bench, it’s the turn of Splatterhouse.

It was told me that PCB didn’t boot at all giving only a black screen.First thing I do before powering up a faulty board is to check for shorts with a multimeter.Indeed, this PCB showed a dead short between VCC and GND.Since boardset is made of a CPU and ROM board, I separate them and could locate the short on the ROM board while CPU one was succesfully tested.

I removed all the EPROMs and MASK ROM but short was still here.Usually components prone to go shorted are ceramic capacitors and seminconductors like diodes, transistors.Inspecting the board I noticed a diode on the right of the JAMMA connector @D1.According the schematics it’s a 6.2 zener diode (type 1Z6.2 from Toshiba).Its datasheet says that it’s used as transient suppressor so to protect devices from voltage spikes:

https://www.jammarcade.net/files/Datasheets/1Z6.2.pdf

Obviously, since cathode of diode was tied to VCC and anode to GND (a zener diode must be polarized inversely in order to do its job) I read it in circuit as shorted.But, when I lifted one lead, the short on PCB was cleared :

So this diode was the culprit :

Once removed the short, the PCB booted stuck on this screen:

SInce I experienced similar issue on other Namco System 1 boards, I could quickly trace this to a bad custom ’64A1′ @M4:

Replacing it with a properly programmed HD63701 MCU (see article on our guide section) fixed the board:

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