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techknight

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  1. techknight

    Anyone have a 12" Monochrome Display?

    Ok, I get it now. seems as if this monitor and the Classic analog board were probably engineered, if not manufactured by the same company. and your right, the 18V zener supplies the necessary VCC for the switching IC. if the 18V zener is shorted, it was either caused by a surge, or the failure of the 4605. Either way, the 4605 probably took some damage. Keep an eye on Pin 1 because its waveform vs the internal reference voltage is critical for the circuit to go into regulation. anything there out of the norm will tell you if its going into undervolt, overvolt, overcurrent, loop loss, etc... Set your scope on dual trace mode as you have it, and reference each channel to pins 1 and 7. See whats going on, compare against operation details of the TDA4605 datasheet. Only way your going to nail this sucker. Obviously safety first since your on the hot side of the system, isolation transformer on the scope is a must. Also the VCC input has undervolt protection as well, so when the supply cycles up, if the VCC doesn't come up to a certain point, it locks out as well. I like the datasheet of these older ICs because they explain paragraph by paragraph setp by step exactly how the IC works and what you should expect during normal, and overload/no load abnormal operations. One other thought, have you done some basic troubleshooting in the secondaries? Such as making sure the HOT isnt shorted? things like that to rule out overcurrent/undervolt cycling?
  2. techknight

    Recapped Macintosh II will not boot

    Its no surprise it doesnt work. it has quite a bit of trace rot in key areas. Its not chiming or booting because it cannot read ROM. The likely reason it cannot read ROM is the trace rot nearby one of the ROM ICs by the batts. Theres a bunch of it there.
  3. The picture above is a damaged LCD. the glass is physically cracked in the corner = trash. Dont pull used caps. replace them with new. if you replace them with one from another LCDs your stuffing in bad for bad.
  4. I love the initiative, But, in my world I have learned that if I have to go through all the effort/labor of removing the ICs, I just change them.
  5. The fact that you rigged in a 3rd party power supply has me suspicious. For S&G, I would hardwire the soft power and see if it stays up and actually boots up. Or if it shuts down again (not enough power)
  6. They are most certainly NOT tantalums. they are plastic encased aluminum electrolytics. you can see the corrosion where they need changed.
  7. did you change UE8 on the logic board? As much as I like Dead Mac Scrolls, its 25 years + out of date and doesnt help with modern day failures due to simply age and cap leakage.
  8. techknight

    SE/30 - ceramic recap causing distorted audio?

    Needs cleaned, and the Address/Data lines need checked on the ASC. the ASC itself could be bad, but I havent seen one personally being bad. Check to see if you have serial port issues too, try and form a localtalk network if you have another machine and a cable.
  9. techknight

    Anyone have a 12" Monochrome Display?

    No this was circa 2005 or so, bak when I was first expiramenting with trying to run VGA on an SE. (which didnt work obviously, but the lower resolutions did).
  10. techknight

    Anyone have a 12" Monochrome Display?

    I have had the original neck board in an SE showing grayscale pretty decently. I have to jog my memory on how I did it, but I did.
  11. techknight

    Anyone have a 12" Monochrome Display?

    I have never seen a schematic or this monitor at all, or know its design. But if RP13 is a pass resistor for a zener diode, its in the Ohms, not K ohms. But that all depends on the current requirement, and the wattage of the original zener. You also need to figure out why that zener shorted, Can you tell me what circuit the 18V Zener is in?
  12. techknight

    what causes LCD rot?

    How would you apply new adhesive without imperfections/bubbles? Then you would need sheet adhesive that bonds clear.
  13. techknight

    Radius pivot 0379 Monitor Issue

    caps caps caps. Vertical circuit caps are usually the first to go due to the high stresses they see. those high current ramp pulses cause a bit of heating in the caps. You need to fix it now rather than later, because I have seen these exact failures actually take out the vertical output IC, and it pops the fuse (if there is one) that feeds it via the flyback transformer. If it doesnt have a fuse, it can take out the whole horiz stage from overcurrent. Depends on how its designed.
  14. It is a known issue for these machines. Any time you get phantom disk drives popping up wanting to be formatted, thats the cause of it.
  15. techknight

    what causes LCD rot?

    You can purchase it online. youll need to get multiple samples and figure which ones work the best. Once the old stuff is off, you can lay the new stuff on behind, and in front. just lay it on there. Eyeball it. check contrast, brightness, etc.. Once you find the best one, then stick with it
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