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About ChildOfCv

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  1. that was the price of owning a PC, we just learned to deal with it. Yep. I remember changing the jumpers to choose ports, IRQs, and DMAs, especially on the Sound Blaster. Early attempts at PnP were a disaster too. We used to call it "Plug and Pray". It took several generations to get that down to a usable level.
  2. Judging by the fact that your chip is getting hot in spite of getting correct voltages (I assume that's searing and not just a little warm?), it is possible that your STIC (AY-3-8900-1) is the problem. The service manual also mentions that as a possible cause of video problems. And wavy text with a vertical line definitely sounds like it's in that category.
  3. Yeah I only got my Colecovision. I don't own an Adam at the moment, but there is a service manual that has the schematics in it, which is of fax quality. In other words, it may still do you some good to continue reversing it yourself, but there is something available for you to compare notes with too. http://adamarchive.org/archive/Adam/Technical/Coleco_ADAM_Technical_Reference_Manual.pdf
  4. I believe it has 2 purposes. 1) Disconnect the VDP completely when external video is activated. 2) Add bias that's necessary for the LM1889 to function properly. The 1889 has the quadrature encoder that sums the two 90-degree-phase-different sine waves after multiplying them by the color difference signals. It's a differential amp that adds Y to R-Y and B-Y and multiplies by their respective sine waves. The internal circuitry of the quadrature encoder requires positive voltages at all times, which it gets from the regulated DC voltage returning on pin 5. And the 1889 also needs the negative bump of B-Y to generate the NTSC color burst signal of 180 degrees. In other words, the 9928's output is tailored specifically to run the LM1889.
  5. I think it's for SCART. They seem to put a resistor beween +5V and pin 16 to choose RGB mode on the TV.
  6. The service manual says that the voltage at pin 2 of the modulator should be 6V. So that sounds normal. So you're using the traditional mod. Did you order it or build it yourself? You should probably check it for solder blobs and such. Also, if the tracks are bare and on the bottom, make sure it's not touching anything metal. And of course the most important question: Without the mod hooked up, does the video distort?
  7. Yeah that's the video chip. It has some special power requirements, apparently. Pin 40 should be -2.25V, pin 17 is ground, and pin 20 is 5.7V. Neither of those should greatly affect the 12V power, but if it's pulling excessive power, it could be affecting all rails. https://console5.com/techwiki/images/c/c3/Intellivision_II_Service_Manual%2C_Model_5872.pdf is the service manual. The allowed voltage ranges on the power board for each output are: TP1,TP2 - 16V-20V TP3 - Ground TP4 - -2.10V to -2.40V TP5 - +5.45V to +5.95V TP6 - +11.5V to +12.5V TP7 - +4.86V to +5.15V TP8 - +21V when off, +5V when on, and 0V while reset held
  8. The real cause of loss of voltage is that the power supply can't keep up with the demands of its load. In a formerly working system, that typically means that something went wrong. But the question is, is it due to something pulling too much power? Or is the supply too weak? Electrolytic capacitors can go bad and short out. But typically when they do, it's because the electrolyte has leaked out. When it does, it stains and corrodes the board. So look closely at the board to see if solder joints or pins are corroded around it, or if there is an odd "spill" around any of them. If so, remove the cap, clean off all of the electrolyte and corrosion, then add a new one. But if a chip is getting hot, it likely pulling power and is the cause of the trouble. Which one?
  9. It does sound like your mod board has a short on it somewhere. What are you using for the mod?
  10. While writing processor tests for my diag board, I was wondering, how much of the chip needs to be tested to clear it of suspicion? Have you encountered a case where some functions worked but others didn't? Or was it always a working or not kind of thing? I am currently testing the address lines, the NMI, INT (with or without interrupts enabled), and HALT modes. The data lines are necessarily tested as part of the process, since bad data lines will give incorrect execution. Beginning CPU test Testing address lines JR 0002 JR 0004 JR 0008 JR 0010 JR 0020 JR 0040 JR 0080 JR 0100 JP 0200 JP 0400 JP 0800 JP 1000 JP 2000 JP 4000 JP 8000 Testing non-maskable interrupts LD SP, 1234 Testing HALT mode HALT <-halt ->int <-halt ->nmi NOP (CPU must ignore this instruction) NOP (CPU must ignore this instruction) RETN Testing maskable interrupts IM 1 EI HALT <-halt ->int NOP (CPU must ignore this instruction) Interrupt acknowledge RETI All CPU tests passed
  11. No, 256 of each. The page register is a full byte.
  12. Okay, I refreshed my memory, then reread my post from the other thread, re-checked the emulator source code, and now I see where wires got crossed. First, all 8 bits of port 42 are significant and select a page, so 16MB is automatically on the table. The confusion comes from discussion of port 60. The lower niyble of port 60 selects which memory is mapped to the upper and the lower half of 64K. The lowest 2 bits specify the lower half of memory and the next 2 bits specify the upper half. The rest of the 4 bits of a write to port 60 are ignored. But I say again, the entire 8 bits of a write to port 42 are used to page memory.
  13. Looks like you shouldn't look exclusively at the 9902 datasheet anyway. You're talking to an entire RS232 card with supporting hardware, not just a chip. Well, not unless you're experimenting with the chip directly. http://www.unige.ch/medecine/nouspikel/ti99/cru.htm#rs232 The 9902 itself only has a CTS input from the terminal. It doesn't enforce any of its own flow control.
  14. The internal pixel clock is actually a division by 2 of the input 10.7MHz clock. So a pixel is 5.3MHz wide, not 3.58MHz. At least according to the VDP datasheet which is known to have many typos and factual errors. So you should key off of the 10.7MHz clock with your own divide-by-2, and also sync with... something. I'd attempt the Hsync signal just to make sure you're on the right step.
  15. Maybe you could synchronize with the sync pulse on the Y output. That should give you a pretty strong indication of which clock cycle gives you the best chance at a clean conversion.
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