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channelmaniac

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Everything posted by channelmaniac

  1. If the outputs are blown badly then the game was plugged into a cabinet that is missing the isolation transformer on the monitor. Some monitors don't require an iso but if you replace the monitor with an older one you must install an isolation transformer. If not, you'll fry the video and sync outputs on the game boards you plug in.
  2. Green = 74LV273 (or HC273) video output latches (commonly blown if isolation transformer is needed but missing) Orange = Video output ladder resistors (commonly blown if isolation transformer is needed but missing) Pink = Stereo output DAC for all audio output The square BGA chip just to the left of the audio DAC is the Intel Atom CPU Just below the CPU and its silver crystal is U32, a serial EEPROM for holding configuration data Just above the CPU is U2, the system RAM U4 and U6 hold the OS and game code Now, IIRC... U7 is the voltage regulator for the core voltage. U36 is the 3.3v voltage regulator You'll want to read the chips carefully as different boards have different chip families. Some use HC, others LV, others LVT, etc... I think the Chinese just used whatever they had on-hand. These things also suffer from horrible soldering. Check the soldering carefully first.
  3. Lucky! I had one here with bad sync... the cheap logic chip was OK. The Altera chip next to it was bad. :( I've fixed a few of these with blown resistors in the video output section. Seems folks like to hook these up in cabs with monitors that require iso transformers, yet they can't be bothered to put one in the cab. It blows the sync and video output sections.
  4. Also, check the ROMs containing the data - in particular, their enable lines.
  5. It's an issue with the Sub CPU. That one controls the images.
  6. Then those 2 PROMs should be fine. Yes. Since you can read the ROMs OK, your data bus overall (/DBUS0-7) should be fine. Focus on the RAM at K3 (/DBUS7 input and the output going through the 74LS04 at J5 - pins 5 and 6 then through the LS367 at pins 6 and 7 to the data bus) If you're referring to pin 40, the CPU, you need to be concerned with the transition from low to high. the /RESET signal is active low - which is what the bar over the signal name means. It should stay low for at least 50ms when powering on the system the go and stay high when running normally. If the /RESET signal is pulsing repeatedly then the CPU cannot boot and the system is repeatedly activating the /RESET signal by means of a watchdog timer. This timer gets reset repeatedly by the CPU when it is running normally. You only see it in action when the CPU can't reset the timer and the timer hits its mark then resets the CPU.
  7. You can't test the 6400 and 6401 PROMs with the Fluke. How are you testing them and determining that they are bad? You would be missing the inputs to N2 which would affect the VBLANK*, /VBLANK*, VRESET, VBLANK, or VSYNC signals coming out of N2 if the 6400 PROM was bad. 6401 is the Address Decoding PROM and you can't read it either, but if you're able to access and read the PROGRAM ROMs successfully then it's working.
  8. You should use newer chips where possible. 9316 is very hard to find but the compatible 74161 is still easily available. - - - Updated - - - Instead of a 9312, perhaps a 74151 - but that one has a different pinout.
  9. There's a hybrid module in the sound section. It has gone bad. There are no replacements.
  10. Boot loop is because CPU 2 or CPU 3 isn't starting up.
  11. ECL runs from -5v and if they are all dead then there was either a catastrophic failure in the power supply or the wrong voltage was connected to the -5v supply to the board.
  12. Don't wait. Get it NOW. You'll hear a distinct difference with racing gates, weak outputs, and more. It'll greatly expand your troubleshooting.
  13. Thanks, I should have a first draft ready over the weekend. I'll just need an email address.
  14. Hey @Kaizen Would you be interested in reviewing a Midway 8080 doc I'm putting together?
  15. EEEEEK!!!! Please put some wire loom or heat shrink over those cap leads to insulate them.
  16. Nice fix! Make a mental note - the 7489 can also be replaced by a 74189 just fine. :)
  17. I cheated and pulled the trigger on a BK570 back when eBay was doing the 10% off, up to $200, coupons early this year. Saved $100 on it. It was still crazy expensive for a small hand-held tester at $900, but that's just 10 Galaga board repairs. :)
  18. If I see horizontal lines on the screen (vertical if you have the monitor oriented correctly for the game) then I start troubleshooting address lines. When you have address line issues you'll the the lines doing that on the screen. Sometimes when you touch the 74LS08s with your logic probe tip the game will boot and start running. Replaced the chip you just touched. :)
  19. Check for video ground missing. Look at the trace on the PCB going to that pin and see if it's missing or damaged. Same thing for the audio. 10 and L are the pins for audio. Both pins should go back to the amp if it's a bridged amplifier. One pin to the amp and one to ground if it's not.
  20. FG terminal is isolated a bit from the foot. I've always been told to connect AC ground to FG and not the foot. It's to protect you in case you get a hot/neutral or hot/ground wiring reversal.
  21. You may need to adjust the capacitors at C33 and C34 - they are connected to between the chip and crystal and ground and C25. The datasheet for the 5205 shows them to be 220pf each, but the value will vary depending on the ceramic oscillator brand you use. It doesn't show to use a cap like the one at C25 so try to remove that one first if the other 2 are 220pf already. I'm assuming you're using a 384KHz ceramic oscillator and not a crystal. If you're using a crystal then you'll need to drop those caps way down in value.
  22. Normal for signal on one but not the other. One drives it and the other receives it.
  23. Make sure the ROM you are using has the sound clip inside and the code to use the OKI chip. You may need to change out the ROMs on the sound board with ones programmed with Williams code.
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