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Mc128k

6502
  • Content Count

    29
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  • Gender
    Male
  • Location
    127.0.0.1
  • Interests
    Everything that thinks with logic and has a screen and a keyboard.
  1. Mc128k

    Macintosh Portable power regulation

    I did not add diodes, they were pre-built in the cable, an official "Apple Hack". They are for both protection and voltage dropping, I can't remember their type, but any rectifier I think will do fine, they don't need special features. They were the black type, not the glass ones.
  2. Mc128k

    Macintosh Portable power regulation

    Weird, I thought I had the first version. As you can see here, the two wires on the right are soldered together and they go directly to the board. I presume that if you had them separated there could be issues when the main battery was connected without a backup battery (the frying you were talking about), so they had them joined while keeping a hot wire and a smaller one. Just a thought. This is the rebuilt cable, as before both wires are soldered at the switch.
  3. Mc128k

    Macintosh Portable power regulation

    No, the wires are soldered together at the microswitch, any failure of the switch shouldn't impact this, the cables remain shorted. They both give 6.5V from the lead acid battery OR the 9V battery when flipping the switch. The 9V voltage is dropped by two diodes on the wire.
  4. Mc128k

    Macintosh Portable power regulation

    Can you post some details on your workbench setup? How are you powering the mac? What voltage exactly? Using the original wires? The portable is a bitch with power control and regulation, most problems can be hunted down to incorrect usage I think.
  5. Mc128k

    Macintosh Portable power regulation

    Another thing, just to update the topic. The lead-acid cells have arrived and I reassembled the battery pack. It just works perfectly, so absolutely no IC/FET/Transistor was harmed during my awful experiments. So... it is done now. Everything in full working order, just like new. I also see that using the bench power supply the computer actually asks for more than 1.5A, so a limiting power brick is mandatory in every case. Like somebody wiser said.. do not use the gray brick. Ever.
  6. Mc128k

    Macintosh Portable power regulation

    About the floppy I would start a new thread, as this isn't related to power regulation. I haven't investigated on it, but if you follow the first scheme I posted you should be able to check if there is power first. 16-18 as you can read from techknight's posts is a hack that kickstarts the IC chip into oscillating. As this is a power-saving IC, it compares the values periodically, and not in a continuous mode. Sometimes it gets stuck it seems, and this trick gets it back to checking the input values. Check out the datasheet if you need more info.
  7. Also try to trace all components from the power plug to the transformer primary coil. I'm not an expert on this, but I suppose that if the power mosfet gets toasted every time maybe it's because it's drawing too much current, and that could be because it's not oscillating. Try to backtrace the gate driver, and debug that part of the circuit.
  8. Mc128k

    Macintosh Classic II Questions

    I have a classic II that needed the recapping. It also happened that some electrolyte corroded a few VIAs and the board had to be lightly bent to make it temporarily work, so make extra attention to the damage BEFORE recapping, take some photos, these could come useful after. Also try to "divide et impera", the mac is composed of two boards, the analog and the digital. First you make sure that the power is good (measure it from the power cable with the logic board disconnected. Then you recap and try searching for issues until you hear the startup chime, and AFTER THAT you debug the screen. And moreover, do some searches for larry pina's books. They are truly fantastic for troubleshooting.
  9. Mc128k

    Macintosh Portable power regulation

    Never followed any guide, I just made it up of pieces I found in the lab. Not-so-much-clean now, I just used it for the damn hard drive. Oh, the white brick works, I'll order the replacement caps anyway.
  10. Mc128k

    Macintosh Portable power regulation

    Guys, I was wrong. I have the white brick, and I'm going to use this of course.
  11. Mc128k

    Macintosh Portable power regulation

    Mine had a gray brick for sure, I just confused it with the others. Didn't know there was a white one. Or maybe it was a replacement
  12. Mc128k

    Macintosh Portable power regulation

    Hoping this could come useful, this is how I fixed the hard drive.
  13. Mc128k

    Macintosh Portable power regulation

    Don't worry, I just removed the heatsinks to check the fet temperature, they are back now. And it wasn't just the switch, when I first connected the lab power supply I attached the wire to the "end" of the switch, bypassing it. It was actually the entire cable that made the mac believe the battery was discharging, it had a high internal resistance. I'm buying the lead-acid cells now, and if I get the right parts I'll repair the power supply. I have many of those around, was it the 1.5A or 2A version?
  14. Mc128k

    Macintosh Portable power regulation

    FOUND THE ORIGINAL PROBLEM THAT WAS THE CAUSE OF EVERYTHING. The power cable. ...yep, corrosion does that too. The switch has some internal resistance. Maybe the wire too. I'll rebuild it from scratch. Likely the computer saw this as a rapidly-discharging battery.
  15. Mc128k

    Macintosh Portable power regulation

    The hard drive had a leaky liquid from the border and a rotten rubber near the magnets. Opened in my homemade clean room, removed the goop and cleaned with alcohol, replaced the rubber with tape, sealed with hot glue. It works beautifully. About the serial port, it was the rightmost, and it suffered injuries from the leaky battery. Four VIAs were destroyed along with some traces, had to rebuild them up, and now it sees LocalTalk and (or) the printer. Also cleaned the floppy and started washing all non-electronic parts. I'll reassemble it soon. If it could be useful for somebody else (as rotten VIAs are very common), to perforate the VIA I used a modified needle (made it thinner with a drill) and inserted it into the hole. Just use it as a drill bit, rotate and press lightly. Very useful in the case of holes filled up with oxide or battery goo. This can perforate solder if at the other side there is a contact pad. After making the hole, use an insulated copper wire (take it from a transformer) to connect the sides. Scratch the traces and solder the wire to them.
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