Golden Axe repair log #4

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Dec 292016
 

I received a Golden Axe system 16 boardset, advertised as untested. When it arrived, it booted to a black screen. It still had a custom Sega encrypted CPU on board,  which means it likely suicided. I swapped in a stock 68000 CPU and desuicided the rom board by reprogramming decrypted program roms. The board booted up with full audio and at a glance seemed to play fine… until I started a game. Immediately I noticed the backgrounds were fine, but all of the sprites were “squished” into a one-row column of pixels. Unfortunately I did not take a photo when the PCB was in this state. I was able to observe the column of pixels changing color, which told me this was likely a complex logic problem, and not ram/ TTL logic related.

I turned to the schematic and the mame source code. I quickly learned that the 315-5196 custom Sega IC was responsible for sprite generation. In my parts PCB inventory, I have a nice condition System 16 motherboard where the corners have been snapped clear off (25+ traces damaged).  It was perfect to pull the suspected faulty IC.

Using my hot air gun, I removed both the suspected bad IC, and the donor IC.

And then I prepped the board for install (also with hot air gun). The chip went in without a problem, I heated the area until the solder was liquid, and carefully dropped the donor chip into place.

The result… total SUCCESS! Graphics are fully restored, game plays 100%. Repair complete.

 

Vendetta repair log #4 – Bad Audio Samples

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Dec 292016
 

I received a “fully working” Vendetta PCB off of eBay for a reasonable price. Unfortunately when the board showed up, I immediately noticed there was something wrong with the audio. Any time a speech sample tried to play, it sounded like a static explosion! I unfortunately (maybe a good thing lol) did not capture the ear-splitting bad-audio state with video, but trust me, it was terrible!

Like most audio issues, I started with the basics. The capacitors checked out OK. Since the BGM was fine, I didn’t need to test the FM section of the audio circuit. I tested the Op Amps and observed the audio was bad at this stage as well (so that told me the amplification section of the audio circuit was likely OK).

I did not find a dedicated DAC chip on board, which is likely where the fault was going to be. I did some research and discovered the Konami 053260 IC is responsible for digital analogue conversion (DAC).

I was certain this chip was faulty, however I sadly did not have a donor on hand. After doing some research, it would seem Golfing Greats and Roller Games both have this IC on board, and they are both relatively inexpensive. I found a faulty Roller Games PCB for a reasonable price, and decided to purchase it to use as a donor for my Vendetta. I pulled out the hot air and swapped the IC:

 

SUCCESS! All audio has been restored and the digital samples are playing crystal clear!

Golden Axe 2 – The Revenge of Death Adder repair log #2 – No Sync

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Dec 292016
 

I received a faulty Golden Axe 2 PCB off of eBay. It arrived as advertised, very good condition, however the video sync is faulty. The seller said that he wasn’t sure if it was his equipment or if the PCB was faulty. The price was nice, so I decided to take a gamble. Unfortunately when the PCB showed up, it turned out the seller was correct – the sync was completely trashed regardless of the monitor used:

I traced the sync signal starting at the jamma edge. This was actually surprisingly difficult to do, largely due to the very small traces Sega used, not to mention the signal starts on the solder side and ends on the parts side (switching sides a few times). After some poking around, I found the sync signal goes DIRECTLY to IC73 (Sega 315-5388). Mame source notes describe this as a “sprite mixer”. Since the sync signal goes directly to pin 42 of this IC (with literally nothing but a ferrite cap in between), I decided this IC was likely faulty. Out comes the hot air…

I pulled a donor IC from another Sega System 32 motherboard that I have that has sustained damage to the PCB. It is beyond repair, but great for donating IC’s such as the 315-5388! I installed the freshly pulled IC to Golden Axe’s motherboard:

  

SUCCESS! The Sync signal has been restored, not other faults are observed. Game is now fixed, working 100%. Another great game has been saved!

 

Gradius II: Gofer no Yabou repair log #2 – Missing Drums

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Dec 292016
 

I received a very nice condition Gradius II: Gofer no Yabou pcb from my good friend Robotype. It was sold to me as faulty, described as “the drums are missing from the audio”. The game showed up, and YUP, the drums are certainly missing!

This was an ESPECIALLY odd fault. In my experience, the Background Music and Samples either work or they do not work. I have never seen working, but instruments missing! I started with the logical audio failure points… YM2151  FM synthesizer (tested OK), YM3012 Digital Analogue converter (tested OK) and finally the UPC324 Op Amps (also tested OK). With all of the major audio failure points checking out OK, I decided it was time to try a more aggressive strategy. I turned to the mame source, and determined Konami Custom ‘007232’ is responsible for audio generation. This seemed like a good starting point… luckily for me, my scrap X-Men PCB had this IC present. Time to remove and swap the IC!

SUCCESS! The newly fitted ‘007232’ custom Konami Audio IC did the trick, the drum line is fully restored and the BGM is back in all of its awesome glory. Job done!

SEGA ST-V repair log #2

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Dec 292016
 

I’ve had the same Sega ST-V motherboard in my collection for quite some time now. Randomly one day, the board booted up with completely scratchy / static audio. At first I suspected the capacitors since the fault developed in my possession, however they were not the culprit. I put the board in storage to return to it another day.

Fast forward a few months, my friend Jassen pinged me asking if I could look at his ST-V. He described his board was having scratchy audio (same fault my board is exhibiting). To my surprise, Jassen informed me he contacted Ken @ irepairsega.com, and was advised that the TDA138 DAC Audio IC was likely the culprit. We all know Ken is a GOD when it comes to Sega repairs, so this information was likely spot on…

We ordered a couple of IC’s (one for each ST-V). Once they arrived from China, I pulled out the hot air gun and went to work:

  

I successfully installed the DAC’s (one on each ST-V motherboard):

 

SUCCESS! The scratchy samples are now completely gone (on both boards), and the audio is nice again. Being that I repaired two boards with the exact same fault at the same time, if you experience and ST-V with bad audio, start with the DAC!

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