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techknight

68LC040
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  1. techknight

    Apple Color Plus 14" Display - Switch Problem

    you have to look at the original switch and get a part number, its the only way to find out if there are any cross references or availability of existing components. What fails is the plastic. there is a pin on the top of the switch that rides in the groove of the plunger itself, and it is a latch/unlatch mechanism. Sometimes the pin breaks and disappears, or the plastic cracks and breaks so the pin just falls straight through in the lastched position causing it to unlatch.
  2. techknight

    Mac Classic Oscillator needs to be jump started

    +1 you have a bad crystal or capacitor likely. Another thing is potential cap goo adding parasitics to the circuit causing a problem. the chip itself should have enough kick to start the oscillation unless it cant overcome the parisitics.
  3. I wonder if you had an unstable power supply and that caused the weird cascade failure. That is strange.
  4. definitely capacitor related issues in the vertical deflection circuitry. you have a bad one, or multiple bad ones. If you dont take care of it soon, you risk damaging the vertical output IC.
  5. techknight

    DuoDock power supply issue

    One thing: You missed 3 other caps in the primary side of the power supply. This will cause your issue too. Especially the one to the left of the heatsink below the power transformer. Otherwise, power supplies that fail to start, or start and then shut down, take a look at the 6-pin opto-coupler in the center of your picture there. if there are no other bad caps or detected shorts on the secondary side of the PCB (like rectifiers, etc) then change out that optoisolator. Common problem with the TAM anyways. that, and the 3-pin standby switcher.
  6. techknight

    Portable 26-pin monitor cable broken

    If only we could do the backlit cables this way. I know the chinese offer flat flex cable services, so maybe I or Bolle could redesign the cable and have the Chinese run it. Just move your connectors over from the old cable to the new.
  7. techknight

    SE/30 project

    its probably broken traces between ICs within the vicinity of UE8
  8. techknight

    Portable 26-pin monitor cable broken

    ultra-ata style PATA cable. (not so modern anymore) will work here. youll have to carefully pull the connectors apart and recrimp. At least its not the backlit version, otherwise you would be hosed.
  9. techknight

    Challenging SE/30 logic repair.

    Yea, I feel you there. I had to get out of it honestly due to life changes and work.
  10. techknight

    SE/30 video issue that has ME stumped!

    No problem! At least the issue is resolved. I can finally get this board back to its owner.
  11. techknight

    Challenging SE/30 logic repair.

    Hard to say, it will all determine where its at in ROM. the CPU is attempting to execute code. But its dying off somewhere. Probably trying to initialize a hardware peripheral and keeps running into the address error or bus error trap handler exception. if you remove the ROM, it should attempt to walk the bus. so monitor the address lines and make sure. It should treat it as an OR.I instruction so itll just keep going. However if not, then see below: You can also make a nop-inserter ROM Simm, (basically hardwiring $4E71 on the data bus, but driving with only pull-up resistors to prevent bus contention when others are selected) and watch the address lines like a counter. they should all be div/2 from each other. you would check these at all peripherals. Also watch these lines with an oscilloscope. you need to make sure each data bit and address lines are able to drive to the full bus voltage without contention issues.
  12. techknight

    Macintosh 128K - no video and humming sound

    LS166 seems to be a super common problem in vintage arcade hardware too. Must have had a bad run of those ICs.
  13. techknight

    Portable Trackball and Keyboard Pinout

    Only the trackball is ADB. the Keyboard is scancode based and requires a controller to be used on something else.
  14. techknight

    Challenging SE/30 logic repair.

    Check the traces between the ROM and back to the ADC/SWIM/SCSI. As well as check the ASC between the GLU. Also, Check D-line to D-line for shorts, as well as A-line to A-line for shorts. as well as to both VCC and GND If that fails, grab an oscilloscope and probe the data lines for activity, and more importantly, bus contention. Also if the SWIM goes bad, it will hold up the boot process. Same with the ASC if it cant be communicated to properly. SCC wont matter, it would just freeze system 7 before it reaches the desktop. Last but not least, check the interrupt lines on the VIA as well as all 3 IPL lines into the CPU to make sure they arnt being held in a stuck interrupt state.
  15. techknight

    SE/30 video issue that has ME stumped!

    Not in all cases. See below: Guys, I can finally put this thread to rest. Should be pinned because its something I overlooked in the beginning and this is one of those times when TTL vs CMOS is hyper critical. In some cases, I have used these parts interchangeably for years and never had an issue, but this is the one case where it became an issue. I removed the HC166 that was on the PCB from a previous attempted repair, and replaced it with the correct LS166 and the issue is now RESOLVED. It is fixed. Works perfect. So thanks for the idea, I thought I had already looked and checked for that beforehand, but guess not. haha This is the one time where TTL vs CMOS had gotten me, and its super important information for others to know. So finally after all these years, I can bring this thread to a close.
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