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About Tut

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    Combat Commando
  1. Hi SainT, please add me to the list. Many thanks
  2. Hi all, I just got a Neo Geo CD that didn't read discs. After close inspection I soon realised that something on the CD-drive board was burnt. It was a transistor in DPAK package labelled D1758. I've basically replaced this and retraced some burnt traces around it. There's also a diode next to it that looks burnt as well (I've checked with the multimeter and it definitely looks blown). The thing is I don't know what kind of diode should I be looking for as a replacement. On the PCB, the diode is labelled as ZD101, and the diode itself has a "J2" written on top. I've done some research but I haven't found any info relating to this "J2" nomenclature. I assume it's a zener? Could anyone please give me some more info on what I should buy to replace it? That'd be much appreciated. Thanks so much.
  3. I suppose that swapping the ROM shouldn't be a problem (I recently changed the cartridge slot of another Jag without problems). I just wanted to know if its worth the try. I think I'll test all the GNDs, do a general reflow and, if it doesn't change anything, I'll try the ROM swap. I know it's difficult with just a multimeter, but I always hate it when I have to trash old glories! So I'll try my best. I'll keep you posted. Thanks a lot.
  4. Is it possible to narrow down the ICs that might be involved? Do you think it's worth trying a Bios swap? I can desolder u35 from another jaguar that has the same Cpu version (1.0) and try it on this one. Cheers
  5. Hi, thanks very much. I'll post a picture of the pcb, but I can assure you that it looks like new. I've checked traces with magnifier and I just retraced one thing that I found suspicious next to the DB15 ports, but there isn't the slightest trace of rust in this pcb. The PSU I am using works well with other Jaguars, so that shouldn't be a problem. I've tested all the Vcc on all the chips and all have their 5v+. Since it took a while to test, both Tom & Jerry got warm but not the kind of temperatures that could hint at a short (the DSP got warmer than the CPU, I hope that's normal). I noticed, though, that U35 was not outputting anything at pins 2,3,4,6,7,8,9,10,11 and others (the other Jaguar that I'm using as a reference outputs voltages around 2v in these pins). Does anyone know what these pins are? Or what the cause of these pins not outputting anything might be? I've taken a look at the schematics, but, apart from tracing circuits, I don't know much about what each signal is doing. Thanks again T
  6. Hi, thanks for your answers. Sorry, yes, the RGB are before the encoder. There doesn't seem to be any sound when the system boots (at least that I can hear when plugged into my TV). All I get is the kind of "spark" noise when I fire it up and the rest is white noise. Where could I start looking at? Maybe U35 to see if the system boots at all? Any measures that you think I could test first? I don't have an osc, just a multimeter. Thanks again T
  7. Hello everyone, Now it's been a week that I've been tinkering with a Jag that wouldn't start. After trying all the basics, checking traces, caps and testing all the regulators, I came to the conclusion that the machine was working but that the LED wasn't (I could even hear the coil hissing). Today I soldered a new LED and it lit on. I also changed U38 and cap 134 just in case. There are no chips getting extremely hot or anything that would lead me to think there's a short. The thing is that I don't get any video output (I use the Scart cable). I've checked all the pins of the MC13077DW encoder and I've compared the readings with those of another working Jag that I've got at home. All the readings are OK except for the composite output (pin 2); the S-Luma output (pin 3);and the "clam" pins (that is, pins 5,15 and 16). The Chroma out (pin 17) also seems a bit low compared to the working one (1,5v instead of 2,1v). The RGB inputs, clk, sync etc seem fine (I just can check voltages), so I assume that Tom & Jerry are working properly. Before I buy a new encoder and change it, do you think that the encoder is the culprit? Or have you come across similar cases with something else being the problem? (I've taken a look at the encoder datasheet but I'm not very familiar with this stuff so any opinions will be more than welcome). Thanks very much in advance! T
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