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w00tguy

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About w00tguy

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    Combat Commando
  1. If I understand correctly, the Vcc test (pins 3 & 4 on U38) indicated the chip was outputting 0.2v instead of 5v. Still strange that it looked completely fine. After browsing these forums I was expecting to see burn marks on the chip or a blown capacitor.
  2. The diagnosis was correct. Replacing the voltage regulator fixed this console! I used a hot air rework station and had no trouble at all (after practicing on a dead motherboard a few times).
  3. I did order one already, but luckily LM78L05 is outputting 5v as expected.
  4. After looking at the circuit diagram I found R168 and followed the trace from pin 2 on U38 to the same resistor I tested earlier. Still getting 9v there. You're correct that I tested the wrong place for Vcc. Looking at the schematic now, pins 3 and 4 on U38 should work for a proper Vcc test. I'm getting 0.2v there, not 5v. This is the exact same reading I get across C150 (the biggest cap next to L29). That must mean something is wrong with U38. I think the bad-solder-joint thread you're remembering is this one. The OP was able to get their Jaguar to power on by shorting pins 9+10 or 15+16 on U38. I've tried shorting 8+9, 9+10, 10+11, and 15+16 with no positive results. I also tried shorting each pin on U38 to their PCB pads and applying pressure to the chip but the system never powered up. Continuity between pins 8-11 and from 8+10 to R169 is fine. I think it's safe to say my U38 is dead. I don't yet have any soldering tools or skills to replace the chip, but I'll report back when the job is done. Thanks again for the help.
  5. Good to know those resistors capacitors and wire are officially done. I'll get that RAM chip cleaned up later. I've got a cartridge inserted and I assume it's connected properly since the cart-related voltage test (U38 pin 2 & 4) passed. I admit I didn't know these systems needed a cart to turn on at first.
  6. Thanks for the info. I wasn't sure where to begin. I think you're right about the extra resistors and wire. While searching I saw that someone else has a motherboard with the same connections. I'm still worried about the mystery gunk on the pins and PCB around the RAM chip though. 1) The power supply is good. 9v and 1.45 amps. It works on my genesis. 2) The switch appears to be working, but I'm not sure how to test it. I get 0.5v, 3v, 5v, 6v, and 9v when testing random combinations of the 6 pins. 3) Nothing seems visually wrong with the IC or C134, but here are the results of some tests you said to try in other threads: From this thread: I get 0v between pin 2 (CART_IN) and 4 (GND) on U38, and a near-zero reading for continuity between pin 2 of U38 and the anode of SD1. I guess this confirms that the switch and cart are OK. Later in the thread you say to check the voltage across C150. I'm getting 0.2v across this and you say it should be around 5v. Does this alone mean the U38 is bad? In another thread you suggest some other tests: 1) Where is R168? If it's the one directly under U38 with "103" written on it then I'm getting 9v across that. 2) 9v 3) 9v 4) 5v (REG1) according to a later post, those voltages are expected. So, it looks like the only test that failed was the C150 one. Time to replace the U38 chip? What about C150 and C134?
  7. This is embarrassing. I recently bought a Jaguar on ebay thinking it was working (for a great price!) but it turns out I didn't read the listing carefully. It doesn't power on. Anyway, I opened it up to look for anything obviously wrong and I see someone has worked on this thing before. One of the RAM chips has a couple of resistors bridging the Vss pins to the UWE/LWE pins (read enable/write enable). This chip has some corrosion/gunk on and around it. I also see a blue wire connecting one of the pins on U11 to TP3 (no idea what either of these are for). I don't know why either of these modifications were done (neither does the seller). Maybe those chips were failing and that happened to fix them for a while? Maybe this is a normal mod people do to these consoles? I'm new to jaguar and I've never done any hardware troubleshooting like this before. I'm guessing the RAM chip needs replacement, but I don't know how to prove that. Any ideas on what I should do? >Image of the board<
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