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About eDoc

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    Space Invader
  1. That looks great, especially on the digital TV. Would you be able to take a picture on the actual board where you made the mod?
  2. Thanks for offering! I would also appreciate pictures of your system.
  3. Unfortunately, my multimeter does not measure frequency. But I kind of have a feel for where the optimal signal for the variable transformer is. As far as the white inductor goes, I cannot get it to budge inside, so pursuing AV mod might be the best thing, unless there’s a way to bypass the bad inductor like I did with the reset switch. I will try to see if I can get a signal now with AV by resoldering the cable. I’ll report back the results.
  4. @ChildOfCv It’s not perfect, but we have a breakthrough! I cleaned up the solder, removed reset switch, and soldered wires on there instead. Plugged in the system, touched the wires and boom! I got sound in the speaker, sound when I push the fire buttons and I have a visual! As you suggested, the system was in a continuous state of reset. This system has definitely been messed with before. The only thing is, I can’t seemed to tune in the signal (i desoldered av cable and i’m back with using RF to test this). I’m making small adjustments with the variable transformer and the orange inductor, but can’t seem to get a clear picture. The best I get is when game 4 is selected (last pic), but game 1-3 all have bad static.
  5. Well, I believe I have a faulty reset button. I slowly cycled through the entire range of the variable transformer while pressing the reset button and nothing happened. No flicker of the tv, nothing. I tried it through both RF and AV cable. That said, the reset button never seemed to do anything initially when I was getting a flickering signal. Also, it looks corroded around the top and actually has a broken off prong (it’s only soldered to the board by 1 prong). I tested its continuity to the chip and that’s fine, so it may just be bad. (I attached photos to see for your self).
  6. Ah, yes, I am missing that from my board. Although, there’s no evidence of solder there so it’s hard to believe I ever had one on my board unless someone did an exceptional job of cleaning the solder up. I am beginning to suspect the issue is power related or is a bad chip. I first thought the reason I wasn’t getting sound from the internal speakers was because the audio signal was first going into the (faulty) RF modulator, then going to the speakers. And because the modulator was faulty, there would be no audio output from the modulator. But, according to your (very awesome) schematic, it looks like the speakers are entirely separate from the RF modulator. Because the speaker makes some noise when I first turn the system on, it seems like it’s getting power. It seems to me like it’s the chip not outputting any signals across the board. I’ll reflow the chip’s solder and see if that does anything.
  7. Do you mean the small box with the flathead screw adjuster circles in red. If so, then yes I have it. As far as sound goes, no. When I plug the system in, the speaker makes a soft pop like it’s on, but no other sound. It used to when it would show static, but there’s nothing now.
  8. Also, where I have the yellow cable soldered in the photo, I am reading 0.95 volts.
  9. Ah gotcha. Doing that I get 6.86 volts (using power supply w/ system on)
  10. No need to apologize! You and @ChildOfCv have already helped me out immensely and I’ve already learned a lot from this I guess if this was a wider known system, there would be more info on it but there’s just not that much info out there. What are you using to amplify your system in the picture? Did you add something to the board or are you using something already on the board? I also just don’t want to have to put a lot of money into this system because it has some other issues like the reset button looks corroded and it’s missing one of the internal speakers. And I obviously haven’t been able to test the joysticks so they may have issues too. Ok, so on my board I really dont see a single junction point for those 4 resistors (picture attached). Using my multimeter I put the prongs on the points of R2 and C2 where the yellow arrows are pointing and got 0.6 volts.
  11. This is all starting to sound a bit out of my knowledge/skill zone. I was hoping this would be a simple fix like reflowing solder or a simple part replacement. I may just put it off until I come across another cheap junker and switch some parts around.
  12. I believe so. There’s a mode called night battle where it looks like the black tank is hidden.
  13. Thanks for the photos! That all makes sense. So that point which you circled in blue is where the video outputs meet after going through their resistors. I soldered a yellow A.V. cable directly to that spot and soldered ground to the Vss on the chip and nothing appeared on screen (likely due to the amplification issue). I already desoldered that back panel when I was examining the broken RF inductor, so it’s all open. What kind of thing am I looking for to be the amp transistor?
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