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Everything posted by techknight

  1. techknight

    SE/30 video issue that has ME stumped!

    So, I pulled out that board, I had to remember where it was as its been a couple years. Sure enough, it has an HC166 in there. Didnt even think about it honestly. I checked my stashed that I was using and all of mine are LS166s like they are supposed to be.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. techknight

    Repairing broken plastic spacers on Macintosh SE

    Which particular one by chance? There are many.
  10. 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.
  11. 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.
  12. 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.
  13. techknight

    Mac Classic II starts to grey screen

    But... not without fresh caps!
  14. 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!
  15. 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)
  16. techknight

    Dead Powerbook 170 - Help about the resistor

    Looks like a 220 ohm. But, I would have to double-check some of my parts boards to be sure. However, I would follow what circuitry that resistor goes to, if I were you. However, I fear the outcome will be grim at best. Resistors dont burn up like that unless something shorts and fails.
  17. techknight

    Powerbook 3400c Logic Board Help

    Display artifacts is almost always bad RAM/VRAM.
  18. techknight

    PBD 270c shuts down mid startup

    Probably the power brick. Bet it needs new caps. Also, make sure the battery is removed out of the unit. This can cause issues as well.
  19. techknight

    My SE/30 died!

    just a couple years ago they were only maybe 10 to 20 bucks. the demand probably sent the prices soaring through the roof. The "lightning bolt" effect you saw was a sudden loss of scan voltage without the beam killer circuit activating. Aka, the horizontal stage failed in some weird way. Or even the power supply's 12v rail disappeared.
  20. techknight

    Color Classic VGA Mod. the CORRECT way

    Because this method was discovered on a prototype analog board that Apple's engineers themselves did to achieve 640x480
  21. I documented the changes to the Color Classic Analog Board to allow the board to operate at 640x480 without the transformer trace cut mod! Here are the CORRECT changes, this allows for full width without any distortions. CL9: Change from 3.3uF to 2.2uF 160V CL10: Change from 3.3uF to 1.8uF 160V DL21 and DL22 get removed and replaced with single 18V Zener at DL21. BZX85C18 RL62 Changes from 47Ohm to 100Ohm RP61 gets 7.5K 3Watt resistor added. J104 jumper gets removed and replaced with a 10 ohm resistor, 2 Watt. RL70 changes from 33K to 22K. RL54 changes from 33Ohms to 15Ohms RP8 Changes from 15K to 33K RP23 Changes from 22K to 33K RF14 Changes from 236K to 216K 1% Precision resistor. J78 moves to J79. (SMD) RP6 changes from 4.52K to 5.11K (SMD) I have yet to try these modifications on my CC board, HOWEVER these changes were performed on a DVT board by one of the head engineers, and the board is working properly at 640x480 without any distortions or width problems. These were the ONLY changes found between the two boards. Also, DL21/22 does NOT overheat on the DVT board either with these changes, the changes never made it into production on the CC, but have on the LC5XX+ When i complete the restoration on the DVT board, I will post photos of a stock, and DVT. you will clearly see the changes.
  22. techknight

    68K (no Mac) Designs OK?

    Thanks for the advice, Yea going forward I will need a standard C library. Appears from research that it requires a board support package at minimum, Which of course it will need since it isnt gonna know what bus it has, where everything is, how to initialize everything, etc. So, I am thinking I almost need a skeleton of a BSP package.
  23. techknight

    SE/30 Logic Board Resurrection

    I know on the Portable if the SWIM is removed or bad, you get the same results. Either way, cap goo loves to eat the traces going into the SCSI IC so check that as well.
  24. techknight

    This Does Not Compute SE/30

    RAM will get ya every time. But that still doesnt explain the lack of audio. Not being able to hear the death chimes kinda sorta led me thinking down the wrong path.