Yesterday I dumped the four PALs from a Ken-Go PCB (an undumped revision on Irem M84 hardware, it will be included in the next MAME release).They differ to the ones already on database except for the one @IC5 which is the same.Dumps have been successfully tested on GAL16V8 targeting devices.
A while back it was identified that the replacement GAL I made for the Amstrad 6128 didn’t play nice with some/all memory expansions.
As I wasn’t able to test any expansions it was always a bit of a concern.
Anyway Gerald over on the CPCwiki forum has revised the equations and has fixed the issue. It was being caused by some improper use of the RAMDIS signal.
Thanks to Gerald for fixing this.
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.
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.
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! 🙂
