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ChildOfCv

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About ChildOfCv

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  1. I see (now). So I guess the choice of games is limited to using a common banking scheme then. Unless you patch the ROM. Anyway, the banking is almost certainly different from the game selection.
  2. I'm surprised it needs any ICs for banking. If it's a 32K chip, it only needs 2 lines connected to switches. The rest of them connect as usual to the Atari. So it would be interesting to find out what the ICs are there for.
  3. Cool. I guess the power supplies you tried have a shutdown mode if they think they are being over-taxed, and your game selection was right on that border.
  4. Not good. Even the main power supply is pulled down to 3V? Just to make sure, C26 should be that huge capacitor. The smaller, tall one nearby is C37. How many amps can your meter measure? Assuming it can measure a good amount, like, say, 10A: Place the meter in amps mode and connect the input power + side through the meter. + would connect to the power supply wire and - would connect to the power input for the Atari. Turn it on with a good vs bad game and see what the input current peaks at.
  5. Q4 is the audio modulator transistor. The LED power comes straight after the power switch. R57 keeps it from blowing up from 9V+ input. You should keep the meter on C26's hot side to see if the voltage fluctuates while the system keeps resetting. If it's holding solid, try the higher voltage side of R57. If the voltage is unstable at R57, it could be that the power switch is dirty.
  6. Well according to Kevtris's 2600 Jr schematics, the LED comes straight off the power input. So if it's dimming, you have power problems. As far as the capacitors go, bulges are one sign of failure but another is fluid stains underneath. Do you see anything like that? It may sound strange, but if you have a mechanical volt meter, it may shed some light on the power issue since the meter's movement is instantaneous. Of course, if you have a virtual analog or fast response meter like what comes on a Meterman, that's potentially good too. But I would expect to see some wild voltage swings while the system is doing its LED dimming.
  7. It would be useful to see a high res picture of the board where the work was done too. Assuming that soldering isn't the issue, there doesn't seem to be a correlation between ROM size and whether or not it works, so the next best issue may be the RAM (which is contained in the 6532).
  8. From what you've noted so far, it seems that replacing the 6532 is the first order of business. And since its port B also affects the pull-ups for 2600 mode, it may be the entire problem.
  9. TTL spec says anything 2V or above is high. And for the joystick inputs, the multiplexer doesn't identify the voltage as high or low. It's merely a relay that simulates connects plugging in one joystick or the other. That's what makes this a nice design, if it is made to work. But still, the 6532 of the 2600 has internal pull-ups on each line in input mode. So it should be reading near 5V on the joystick inputs at least. Then the 2600 adds a 10K pull-up resistor for the button. The 7800 should also have that pull-up on the joystick lines since it also uses the 6532.
  10. That looks like the Ben Heck hack with a couple of components to attempt to compensate for the additional power draw. Its biggest issue was that the transistor works too hard. The new board looks like an op-amp, which the original circuit should hardly even notice, and it handles the power better.
  11. Do you implement the SN76489AN access delay correctly? When you first raise CS for the chip, it raises WAIT for a number of clock cycles. The CPU will wait until that line goes inactive again before it finishes the data write cycle.
  12. If the programmer takes direct control of the output, then the programmer sets the pitch implicitly by the alternation of the volume. If you cycle the volume 1000x per second, then you output a 1000Hz signal. That's just inherent to sound generation. The driving controller uses the quadrature inputs for the steering wheel. The foot pedal is just the button. Roller Controller uses both players' quadrature inputs. Off the top of my head, horizontal goes to player 1 and vertical to player 2. The two buttons on the RC correspond to the 2 buttons on the standard controller. Well, Roller Controller actually has 2 modes: In one mode, it does as said above. In the other, it emulates joystick inputs based on direction of roll. I've heard that some do, but I couldn't tell you which ones. RAM, like any other IC, starts up in indeterminate states. Each chip manufactured may have preferences for certain bits at startup, but some bits will still be random. Between chips, there will be no commonality. Some games rely on randomness to give you a different game each time, such as a casino cartridge. And one infamous home-brew checks if memory is randomized to its taste, as a form of DRM.
  13. And question 2: Does the RF connector need to be plugged in on both sides, or is it just sufficient to have something plugged into the CV? If the latter, then it may be a mechanical stress issue.
  14. Anyway, looking at the failure, it seems that U11 is the biggest culprit since everything that's wrong is only off by 1. But it's also not consistent which off-by-1 it is. For instance, "BEFORE" replaces only the first E with a D. That seems to indicate that the Q output is floating rather than shorted. The connection is not making it back to the VDP. Oh wait.... TI, for some reason, reversed the order of the lines so that the least significant bit is D7. It's hard to remember which ones are compensated for, so it could actually be U16 that's the problem. And U16 also has a dedicated Q output to the 9928 which is not multiplexed with an address line. Well, D0 connects to CD7. AD7 connects to VA0. So yeah, it's probably U11 that is suspect. Make sure pin 2 of U11 has continuity with pin 5, and nothing else. On all the other DRAMs, it should only connect to pin 2. On the 9928, it should only connect to pin 3.
  15. Regarding A7: 4164 is a 64Kb chip, but the VDP only uses 16K. The 4116's that came with it use the A7 pin as VCC. It's way easier to just let it be +5V than to change that. A7 needs to be tied to some constant value--0 or +5V. Either one works, but as I say, +5V is easier. I guess it's okay for pin 1 to stay at -5 since it's supposedly not connected inside of the chip. As for A7 (pin 9), it's fine to just tie it to a voltage. It already has meg-ohms of resistance internally anyway. BTW, did you add sockets to the CV board?
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