Received from Germany this mint Liquid Kids PCB (on Taito F2 hardware) for repair:
Board was working fine except for sprites, they had jailbars through:
First of all I dumped the two 4Mbit MASK ROMS which store sprites data, they turned out to be good.This part of graphics is almost entirely generated by a custom ASIC marked ‘TC0200OBJ’ which showed some sign of previous rework on my board :
We can see pinout and implementation of this custom in the Final Blow schematics :
Probing with a scope its outputs data pins revealed some unhealthy signals (shown on the right on the below snapshot, good on the left)
ReproductionsComments Off on Konami ‘503’ reproduction
Sep262018
The Konami ‘503’ is a custom chip we can find on some PCBs from this manufacturer.It comes in a DIP40 package with its part number scratched off in typical Konami style :
You can refer to this spreadsheet (courtesy of user ‘mattosborn’ on KLOV forums) for a list of boards (all with Konami Classic pinout) that carry this custom :
Technically speaking, the IC takes care of part of the sprites handling (along with the other custom ‘502’) as schematics shows :
We already have a modern replacement of the Konami ‘503’ thanks to the wonderful work of people over FPGAArcade forum, this is the thread of reference :
What I made is a “poor man’s” reproduction of this custom chip with no use of CPLD or other complex programmable logics but I simply re-engineered with surface mounted devices the replacement daughterboard (silkscreened ‘KC001’) that Konami used in place of the IC :
Here’s the result:
It works fine on my Track & Field and Kicker PCBs and should do the same in all other boards that use this custom IC.
Technical InfoComments Off on 1Mbit EPROM Confusion – JEDEC VS non-JEDEC
Sep232018
I’m unsure where this all started and who was the first to break the tradition but when it came to the 32 pin 1Mbit EPROM some manufacturers went rogue.
The difference between a JEDEC pinout and a non-JEDEC pinout is two pins swapped. The signals in question are /OE and A16 and the pins are pin 2 and pin 24.
Check out this picture for a visual description
Normally this information would be all we need to know. For example Macronix has the MX27C1000 eprom which has a JEDEC pinout. They also have the MX27C1001 which has a non-JEDEC pinout.
So far so good.
The confusion starts to creep in if you wanted to replace a Macronix MX27C1000 EPROM with say Sony’s CXK27C1000.
Its a natural assumption to make that these two are going to pin compatible but that is where we would be wrong.
Sony’s CXK27C1001 is actually the JEDEC pinout and the CXK27C1000 is the non-JEDEC pinout.
I believe that all manufacturers of the 27C010 use the JEDEC standard pinout.
Here is a table that we have put together that hopefully captures all the variants and their pinout type.
So if your replacing an EPROM of this type then make sure the EPROM you have is the correct pinout or your going to get problems.
Thanks to Caius and Simonden for their help putting the list together.
PCB Repair LogsComments Off on Air Buster : Trouble Speciality Raid Unit repair log #2
Sep172018
Another shoot’em up on the bench and still a PCB received from Portugal.This is the time of Air Buster – Trouble Speciality Raid Unit- released by Kaneko in 1990 .
Board booted to a static grey screen :
Touching the board while powered on I found the IC @D21 was really hot :
The IC is a Nec uPD41101C, a 910-word x 8-bit high-speed line buffer :
The data outputs pins were all stuck low:
I removed the chip and replaced it with a compatible uPD42101 :
The board sprang to life with the power on self test which reported all RAM/ROM devices as good:
But it kept to reset and restart again the POST in an endless loop.Randomly the board gave an error related to the SUB CPU which was generating a not maskable interrupt (NMI)
There are three PLDs on board and the one marked ‘PR-501A’ is involved in SUB CPU circuit :
Probing it revealed some of the outputs were stuck low, they showed few Ohms of resistance to GROUND compared to typical values:
I pulled the IC and read it in my programmer, although the device was protected this would have give me an idea about its functionality.I got a read error which confirmed that it was really bad :
Luckily we have dump of this PAL in our database so I burned the JED in a GAL16V8 and the board finally booted into game.But colors were wrong and sound absent :
The lack of audio was due to a missing OKI MSM6295 and YM3014 DAC:
As for colors issue, piggybacking the two 2k x 8bit palette RAMs lead to some improvement :
So , since the RAMs were also from Sanyo manufacturer (not really reliable in my experience) , I pulled and replaced them although the chips were tested good out-of-circuit.This fixed the issue and board completely.
Bought this game for personal collection with a problem on the RED colour which was completely missing.
Checking the schematics there are some 74541 chips which are sending the colour bits to a resistor network for Dac conversion. The one on the red colour @UC4 was correctly working so I checked the 74ls07@UA4 involved in the blanking circuit.
Pin 2 was always below 0.5V and muted the total red colour
