Got this Explosive Breaker PCB (an unusual shoot’em up from Kaneko) from Portugal for a repair.Board was in good condition but showed some sign of previous rework especially on SMT devices :
On power up the self-test seemed to be successully performed but then an error occured and the board resetted in an endless loop:
Inspecting the board I found that the custom IC marked ‘VU-001’ (involved in Serial EEPROM and dispwitches handling) was burning hot :
The IC seems to be used on very few other Kaneko PCBs but we looked around and found a donor (Magical Crystals, a maze game) which runs on identical hardware:
I replaced the custom with the spare :
Board finally booted into game but screen was blueish:
A predominance of the blue color means that red channel has troubles or is missing.The RGB colors come from the emitters of three NPN transistors:
Probing the base of the red transistor revealed no signal hence the problem was upstream:
The base is tied to the nearby custom marked ‘699205P’ .
As said before all the SMT devices were previously reworked, also this one showed signs of hot air reflow.Inspecting it with a microscope revealed a solder bridge shorting two pins:
I fired up my soldering iron and removed it, this restored the correct colors and fixed board competely.Job done.
I had this original Silkworm PCB (manufactured by Tecmo in 1988) in a trade some years ago :
I didn’t know the status of the board since I never looked at it.Quite confident I powered it up but I was immediately disappointed, a solid static blank screen was all I got:
While I was visually inspecting the board I noticed the 28 pin brown SIL hybrid module marked ‘MA7053’ was a bit wonky:
I slightly wiggled it and it fell off:
I installed some 1.778 female pin headers on the PCB:
and patiently soldered the component on a strip of correspondent male headers:
In this way I got the board booting but with severe graphic faults.Color were wrong, sprites flashing (it’s hard to capture this issue with a camera), vertical lines through screen :
I decided to troubleshoot the sprites issue for first.Studying the hardware I figured out that the line buffer is made of twenty 4164 (64K x 1-bit) dynamic RAMs located on VIDEO board :
Some of them were extremely hot to touch and many showed stuck bit on output:
I pulled them all one by one:
Nine of them failed the out-of-circuit testing:
The graphics were correctly drawn now but the colors still wrong :
Tracing the three colors back from JAMMA connector I figured out the final part of the RGB DAC circuit where I noticed the lack of three resistors @R10-R8-R12 :
I compared my PCB with some pictures online and I had confirm that the three resistors were really missing on my board:
I didn’t know the correct value of these resistors and schematics were not available so I looked at Rygar ones which runs on similar hardware, they were 120 Ohm as part of the R-2R resistor ladder circuits used as RGB DAC:
I installed the resistors :
This fixed board completely:
Mitsubishi ‘MA7053’ reproduction
After repaired the PCB I thought this was a good chance to study a replacement of the ‘MA7053’ custom SIL.As often I do in my reproductions I looked at how possibly the custom was re-engineered.I could find two replacement daughterboards.One used on a bootleg PCB :
The other one was from an original Tecmo board (pictures kindly provided by ‘monsterlair’, thanks again to him)
Design were slightly different but they both have same functionality.Technically speaking the ‘M7053’ provides interface between the Z80 main CPU data bus and video memory latching data too.After figured out schematics of the two daughterboards I re-engineered them with surface mounted devices ending up with this result :
Installed on PCB for testing:
Both designs perfectly works on my newly repaired Silkworm :
The ‘MA7053’ is used for sure on these PCBs:
Gemini Wing
Rygar
Silkworm/ Back Fire
But it could be present also on other Tehkan/Tecmo boards so any addition is welcome from all of you arcade collectors/enthusiasts.
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.
