Repair Logs – Page 56 – JAMMArcade.net

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

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

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

PCB Repair Logs, Repair Logs Comments Off

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!

The Simpsons repair log #2

PCB Repair Logs, Repair Logs Comments Off

Dec 292016

Let me preface this by saying I’ve been really lazy about blogging my repairs this year. I found some free time today and decided now is a good time to post some of my accomplishments. All of the following repairs were performed through out 2016, but not documented until now. Enjoy!

I received a faulty Simpsons PCB off of ebay for a reasonably good price. It was sold simply as not working with the faults not described. Upon receiving the board, I observed it was in very good condition and a worthwhile repair candidate. When I fired t up, the graphics were REALLY bad! As you can see, the backgrounds and most of the sprites are missing:

I was able to run the rom test and self test, all IC’s reported as good (so I was confident there is not a ram or rom issue at hand). I turned to the mame source code to better understand what each of the Konami Hybrid IC’s are responsible for in the graphics section. I learned that 053247 and 053246 are responsible for sprite generation, and decided they would be a good starting point. Fortunately I had a dead XMen parts-PCB with both of these Custom IC’s present. I started by swapping 053246 with the donor from XMen. As you can see below, we’re getting better! But its still not fixed… Backgrounds are rendering but the sprites are now missing.

I decided to move on to the 053247 IC, and attempt swapping that next. I learned that these IC’s work in tandem, and if one is bad, there’s a chance the other is also bad.

With both IC’s changed from the donor Xmen board, all graphics are restored!!!

Repair complete, game now plays 100%. I don’t dare imagine the abuse this PCB received that took out BOTH custom IC’s, but I’m glad its ready to play on. Another gem saved from the scrap bin!

Thunder Dragon 2 repair log

PCB Repair Logs Comments Off

Dec 242016

Got this Thunder Dragon 2 for a repair :

According to the owner, the PCB has suddenly developed a graphic fault, this was confirmed once I powered up the board:

In this close up you can see better the kind of fault:

Some part of foregrounds had missing lines and they were flashing (see clouds in the above video to make an idea of).Not being schematics available, I started to study the hardware and found, that shorting some pins of a CXK5164P RAM @U136 (there are four of them) changed the way the fault appeared:

This is an unusual 22 pin static RAM of 64K x 1-bit manufactured by Sony (usually we encounter 1-bit RAM as dynamic ones) but I could find its datasheet and hence pinout:

All pins were correctly toggling but analyzing with a scope the DATA OUT (pin 9) I found discrepancies with the same signal from the other three RAMs ( good signal on the left, presumed bad one on the right of the below picture):

As you can see, transitions of the right waveform are not regular sign of bad data coming out the device.At this point, I had to order a spare since I had no stock of this unusual static RAM.I had to wait almost a month before getting the right part since at first the seller sent me by mistake some OTP EPROMs.But at the end I received it:

And it was worth the wait since I could finally fix this great shoot ’em up!

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