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techknight

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  1. techknight

    SE/30 video issue that has ME stumped!

    You cant swap in an HC for an LS, because that is TTL vs CMOS, they have very different logic level High and Low thresholds. And yes, I checked for that, although its been a very long time, I can check again as if I recall, I dont know if I was the one who changed the IC.
  2. I use a cheapo ultrasonic chinese special with distilled water (all I can get locally) and I have had ZERO issues. And this is with production PCBs at work. Never once have mineral deposits have been a thing or residues, etc. After it comes out of the ultrasonic cleaner, it gets a dip in the IPA to displace the water, and then it goes into the oven. Works every time.
  3. techknight

    SE/30 Logic Board Resurrection

    if the sound is clear, then we know all the address and data lines are getting to the ASC. So if there are any breaks on the SCSI/SWIM, they are going to be at the junction VIAs. So you should test from the SCSI/SWM back to the ASC, or GLU/CPU/ROM. The breaks typically occur right around the 3 capacitor block in front of the molex, there are no good pics of that area.
  4. Before you fire that thing up, you must reconnect all the grounds back on the CRT board if you want to run it without the shield for troubleshooting. Otherwise you must reinstall and resolder the shield. From looking at the design, the ground shield is the ground that connects everything together, once removed, it will fail to work right.
  5. the noise is indeed caused by the flyback transformer, more specifically, the ferrite core is loose. it actually vibrates and creates the audible tone. has to be shimmed out and siliconed/sealed to prevent it from resonating.
  6. techknight

    Macintosh Classic II display horizontal thin lines

    Yea the blowdryer method is a real good way to troubleshoot bad dried out caps. Just be careful as to not overheat everything. Plenty of heat, but not overheat.
  7. techknight

    Repairing broken plastic spacers on Macintosh SE

    Ahh ok, so the original stuff and not the "plastic weld" stuff they offer. So many options and not a clear cut answer from companies like that, as I see alot of product "overlap" Anyways, Need something for powerbook hinges, and i am sure everyone else does as well.
  8. techknight

    Repairing broken plastic spacers on Macintosh SE

    Which particular one by chance? There are many.
  9. techknight

    Macintosh classic brightness issue

    Classics almost always have to have the caps changed. But variable brightness is usually noise on the control signal, Could be caused by leaking electrolyte, could be caused by bad solder connections on the connector itself, on either end. The brightness signal for the analog board comes from the Logic board, so it could even be that! especially if there is cap goo everywhere. you have to inspect everything.
  10. techknight

    My SE/30 died!

    the initial failure wasnt resolved that took out the first flyback. So I would hate to think about this, but you may have taken out the 2nd one. Not sure what the Hissing sound your describing is, could be many things. Could be diodes, capacitors, anything on the horizontal section, Up until, and including the sync gate logic IC. Without a scope, no way to know what the horizontal drive signal looks like to know if its correct or not. It has to be chased through the stages to find out where it gets screwed up. Because "hissing" means noise, and ALOT of it... Also a broken, gone to air CRT will do that too, but it would be more arcing than hissing.
  11. techknight

    Macintosh Classic II display horizontal thin lines

    Caps are starting to fail in the CRTs too, the 12" RGB version has a known issue with this in the horizontal drive stage. For future reference, the issue you describe are whats known as "retrace lines" The fact that your screen looks like that (Referring to classic II), means your video signal is driven full on. So the CRT is literally biased well into the hot range, as retrace lines are usually blanked by the beam killer. (or blanking interval). So, you either have a video amp IC thats on the classic II analog board thats bad, or the video IC on the logic board is bad. its one of the two. So unless you simply want to go on a parts swapping exercize, you need an oscilloscope to trace the video signal back through to figure out at which point its dying off. The Monochrome LC monitor, it could be anything. My immediate thought is the contrast is way up. Again, biasing the CRT well beyond its range. Also, you could have a video amplifier issue. This almost screams caps, or dirty/bad brightness/contrast pots. Also, much more rarely, and only if someone has messed with it, the G2 (screen) drive on the flyback could be turned way too far and cause the issue as well on CRT monitors. To sniff out bad capacitors, you could simply take the back off, grab a blowdryer, and start heating up the analog board in various areas. Even the CRT neck board if that fails, if the picture begins to improve drastically, then it needs a cap job. Also look for wet/corroded/crusty areas near caps, this gives it away sometimes, but not always.
  12. techknight

    Mac Classic II starts to grey screen

    But... not without fresh caps!
  13. techknight

    SE/30 Logic Board Resurrection

    Yes, but thats how the schematic was laid out. Testing between the SCSI and SWIM is an absolute waste of time, because once you know the PCB like I do, they both connect to each other back to the same vias. You need to test all the way back to the GLU/CPU/ROM section. The other thing is, the ASC and SCC share alof of the same bus connections and traces, How does it sound when its powered on? is the chime clean? or does it sound kinda "dirty"? This is a big clue!
  14. techknight

    Powerbook 3400c Logic Board Help

    well theres a difference between artifacts on the screen (graphics glitches) versus actual backlight brightness. Check the voltage going to the inverter board, it may be low. Also check the control signal to the inverter with an oscilloscope and make sure you have a clean PWM signal and not grounded (That will make it dim too)
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