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About DocSchlock

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    Combat Commando
  1. I was able to do some clock measuring on an oscilloscope and got the following after adjusting C2 (see also attached images): Crystal Output: 7.15814Mhz (xtal-output.bmp) Clock Output from Color chip: 3.57954MHz square wave (color-chip-clk-outout.bmp) Clock Input to STIC chip: 3.57954MHz square wave (stic-clk-input.bmp) Clock output at Cartridge Slot pin 10: 3.57954MHz triangle wave (cart-slot-pin-10.bmp) Is it normal for the cart slot to have a triangle wave form? From the service manual it looks like there's a 5.8K (R4) resistor between the cart pin and clk signal so not sure if that's affecting it.
  2. Thanks, mthompson. I just replaced Q1, Q2 and also C26 (bi-polar) for good measure. Unfortunately, it still has the same black screen output. Continuity between the ROM cartridge and socket pin/board traces appear to be good. It's probably to the point now where I'll need to locate a known good unit and start swapping out chips. I also have access to an oscilloscope but am no expert with it and am not sure what all can be tested other than the clock signal (which is next on the list).
  3. I have an Intellivision INTV System III that doesn't seem to output any video and I'm looking for suggestions of things to try. Here's what I've done so far (part names based on the Console5 Schematic here ) Replaced power supply capacitors: C1, C2 and C3 Replaced main board capacitors: C27, C28, C30 and C40 Before replacing the above components, i would get no video output whatsoever. Only static. After replacing the components, I get a clean black screen and static "blip" if I hit reset. Additional things I've tried and tested: Used contact cleaner on cartridge slot Cleaned the contacts of two games (Poker & BlackJack and Space Armada) but get black screen for both Tried inserting cartridges at various depths for possible better contact Tested voltage for all test points based on this diagram. All were correct except for TP-4 which is supposed to read 16V but was actually 25v (no load) and 18V (when connected to main board). TP-6 which is supposed to read 5.65V was 12V (no load) and 5.9V under load from main board. Are there any ideas on other things to try or is this thing toast?
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