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ChildOfCv

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  1. The audio transformer uses a flat screwdriver but the channel tuner uses a hex head. You would be best off to get a set of tools made for tuning. The tools are plastic so that they don't throw off the tuning while the metal is near the transformer. And they are also less likely to chew up the tuning slug.
  2. Well, one thing I can say is that Motorola's early chip marking SUCKS. I can't look up exact info on what your existing chip is. That said, your specimen is pin-compatible with it. The only remaining question is if it's fast enough. They make a MCM6665-20 and a MCM6665-15. Okay, I see another board that used Mostek (pronounced "mistake") memory. It has a -20 suffix. So that lends some confidence that your -20 memory should work.
  3. Looks like outside interference. Most likely the ground inside of the cable has separated and no longer conducts. If you open the case, use a multimeter to test continuity of the outside conductor where it plugs in, to the RF adapter.
  4. The audio tuning is that hole in the upper right, and the overall channel tuning is in the lower middle. Theoretically you should get the channel tuned correctly until the picture is good. But if the audio is tuned wrong it can still screw up the video too. So it's a game of looking for best quality as you switch between the two. That said, the channel tuner especially has a tuning slug that can be destroyed from using the wrong tool or from excessive wear. Make sure it's complete and not cracked. Either way, it should be fine to send for RGB modding, as the RF part is not required for that.
  5. It is possible at least. You'd likely want to use serial or at least nibble input for each key code. Pins 5 and 8 can be used for clocking. They are inverts of each other. So the scheme could be, toggle pin 5, then read the 4 directions. Then toggle pin 5 and read the 4 directions again, then you have a full byte. You'd need an Arduino or something to act as the USB hub and keycode buffer though.
  6. I wonder if it was heated at all. You can still see the individual grains of solder in that. Well, I guess if the chips are still hanging on, something must have melted though.
  7. The difficult part there is that the final video output amplifier on the EM1 uses +12V. While 5V would provide plenty of room for a video output signal, the amplifier is optimized for +12V, and may need some parts replaced if you wanted to run it on +5V instead (and then it would no longer be compatible with the CV). The -5V may be optional, but it's hard to know without removing it and testing. As for generating a clock signal, there are some blank spots on the board where a NAND gate chip, a crystal, and some resistors and capacitors could be soldered in. Theoretically, this is an onboard clock circuit. There is a jumper that connects the expansion port's clock into the system, but it can be moved to the jumper spot at the output of this circuit. Or you can just forget about all that and do the full replacement like another poster did.
  8. I suspect that the zeners were added because the Coleco controllers may have had different trigger points than the Atari controllers. They're supposed to be somewhat compatible, at least pinout-wise. But maybe these were added to fix potential problems that were caused by the CV controller's diode maze. Come to think of it, I wonder if the number pad on the CV controller has any compatibility with Atari's keypad controller? That said, I still don't understand ZD1's existence, not even in that context. Maybe it's an anti-static measure from plugging the module in.
  9. The next question (after power) is if you're on the correct channel. Usually 3 or 4 for NTSC systems, or 3,4, 35, or 36 for PAL systems. If you're sure you're on the correct channel, and if the cable is fine, the problem could be a bad connection on the ADAM's RF output. Check if it wobbles, which would indicate that its press fit is loose. Another possibility is that the connection from RF board to center pin has broken its connection.
  10. Hmmm. Other than finding a local person who has the tools to look at it, I'd suggest looking for a replacement RIOT then.
  11. Do you happen to have a multi-cart such as Harmony or Ultimate SD? If so, you could load up the Atari test cartridge and see if there's any sign of life.
  12. Well at least the picture is clear. Is this at least an improvement over before? You didn't really describe what was actually showing up before. The pattern shows that the TIA seems to be working like it's supposed to. If left alone, it will copy the same pattern vertically and will mirror the left to the right. It also appears that the clock circuit is working. So what's left is either the CPU, RIOT, or cartridge connector. Did you use sockets as you swapped the chips out?
  13. This virtual strip board should explain what I'm talking about.
  14. The pair of resistors needs to be connected to the same row as the video input and the transistor base. It looks to me like they are both connected to the emitter and output instead. BTW, proper output impedance requires another 68 ohm resistor from emitter to video out. A 470uF capacitor would also be helpful. That "futurewas8bit" article that added the 75 ohm resistor for impedance matching did it wrong.
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