I got a couple of Chequered Flag PCBs for a repair.Here’s the first:

The MASK ROM test reported an error on a character ROM at a certain location:

which caused some garbage on screen:

Launching MAME I could figure out the ROM reported as bad was the one @N16:

Device itself was a non 32 pin non-JEDEC 27C1000 mounted on a custom socket in place of the classic 1Mbit 28 pin MASK ROM.So I read it and it matched the one on MAME sets.Probing it I found that its pin 28 (A13) was silent,I traced it back to the a near custom marked ‘051316’ that addresses the entire character ROM :

A dead address line means that the IC has an internal fault so my only option was to replace it and this is what I did taking it from another dead board:

With a good custom the MASK ROMs test successfully passed and all GFX issues vanished:

The second PCB :

had slight sprites issue.Here’s a comparison with a MAME snapshot (on the left):

A visual inspection of the board revealed some lifted pins of the two ASICs sprites generators:

A reflow was enough to restore correct sprites:

End of (double) job.

I bought this pretty rare Exzisus PCB as faulty from our member Corrado:

For the uninitiated it’s horizontal scrolling shooter arcade game released by Taito Corporation in 1987.There are two PCB version, one not JAMMA with separate RGB outputs for background and sprites, the other with a single video outputs and is JAMMA compliant.The one I got was the latter.

Once powered the board up I immediately noticed two issues : all sprites were horizontal lines shifted and repeated on each half of screen :

and  sound was missing at all (although I could hear some noises sign that amplifier was  good).Studying a bit the hardware, I could figure out how sprites were drawed.The four sprite EPROMS are addressed by a custom, marked ‘TC0010VC’ (there is another one for the backgrounds) while the data were written on two 6116 RAMs which were addressed by the same custom but not directly but through two 74LS273 latches and four 74ALS169 counters:

Probing the latter with my logic comparator I got troubles on the outputs of three of them so, although false readings are quite common for this kind of device I decided to remove them.Tested in my BK560A they all failed:

Once replaced these counters, the sprites were correctly restored:

So I could focus on the sound lack.Connecting an external amplifier to the analog output of the YM3012 DAC I could hear all the sound as well as on the input of the near TL074CN OP-AMP but nothing on its output :

This was confimed also on my analog scope (good input on the left, no output on the right):

Fitted a new TL074CN @J21 restored full sound.End of job.

 

Not a real repair but just a quick “dirty” fix for this Konami Teenage Mutant Hero Turtles PCB :

All was fine but  the music played at the start of a game (when turtles jump from palace) was missing :

A usual I started my troubleshooting with a visual inspection and I found soon the culprit.One of the two 640KHz ceramic resonator was missing:

I took it from a dead donor board :

and once fitted the missing music was restored.End of (small…) job.