August 2018 – Page 2 – JAMMArcade.net

Sunset Riders double repair log

PCB Repair Logs Comments Off

Aug 072018

Recently I had two faulty Sunset Riders (by Konami) PCBs on the bench for repair.The first board came from Portugal:

Board was watchdogging in an endless loop, sign that no valid code was executing by main CPU:

Doing the usual check on CPU/RAM/ROM circuit revealed that a data line of a WORK RAM was stuck low:

Pin was almost shorted to ground:

This is shared with main CPU (pin 1, data line D4) and other devices too.Using a short locator I measured resistance to GROUND of all common points:

The lowest resistance was on pin 7 of a 74LS253 @14B:

The IC failed the out-of-circuit testing:

The board booted up but failed the POST showing a bad device @15B on an upside down screen:

The device concerned is the ER5911 serial EEPROM :

Someone previously replaced and socketed it but managed to rip the rivet of the pad of its pin 4 (which is the data bit output) which lost connection with the rest of board :

Once restored the connection I had to re-initialize the EEPROM:

After this the board successfully booted into game with no further issue.First board fixed.

The second board was in a lot of faulty PCBs I bought:

It booted up but jailbars were present all over the screen:

Lines are a clear sign that something is wrong with the graphics data (in this case the tilemap).I launched a MASK ROM check which found a bad device @16K:

I was about to replace the device when I gave a look on its soldeside and found a deep scratch :

Under a microscope two traces appeared to be severed, they were indeed two data lines of the MASK ROM (pin 13 ‘D0’ and pin 28 ‘D7’).A quick check with a multimeter in continuity confirmed it.

I restored connections with some AWG30 wire:

No more complain of MASK ROM check :

Board 100% fixed and double repair accomplished.

Truxton II repair log

PCB Repair Logs Comments Off

Aug 032018

Yet another Truxton II PCB (overseas release of Tatsuin Oh) on the bench and always from Portugal :

The board was stuck on boot on a colored striped static screen :

Main 68000 CPU was not running, both data/address bus were inactive.For first I checked the ‘GP9001’ custom GFX controller (QFP 208 pin ) which is a common issue on hardware that use it:

I found some lifted pins:

Reflowing them didn’t lead to any improvement.The board uses the ‘infamous’ custom ‘HK-1000’ custom (the early fragile ceramic revision) which handes inputs :

A closer inspection revealed the IC was damaged, some pins were broken at package insertion so beyond repair:

As said, the ‘HK-1000’ handles inputs but a faulty one can prevent the game to boot because some CPU address lines are used to generate the enable signals for it.I removed it:

Without the custom the board successfully booted up but obviously game was not playable due not working controls:

So I installed two strips of 2.54mm female machined pin headers in order to host a reproduction of mine:

The last issue I had to fix was some rustling background noise:

With the help of my audio probe I quickly figured out the sound was clean before reaching the 2.2K sound potentiometer :

I replaced it and this restored a clear sound.As ‘icing on the cake’ I removed an ugly hack to use a quartz instead of an oscillator and installed the proper part:

Yes, yet another Truxton II PCB fixed!

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