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Mc128k

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Everything posted by Mc128k

  1. 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. 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. 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. 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. 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. 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. 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.
  9. 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. Guys, I was wrong. I have the white brick, and I'm going to use this of course.
  11. 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. Hoping this could come useful, this is how I fixed the hard drive.
  13. 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. 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. 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 ro
  16. Haven't posted an answer for a while. The little bitch is now working. I was going to start making the tests you mentioned and after connecting the power supply with a slight higher voltage it actually started remaining on! ...and it holds the hard disk... ...and it boots... ...asks for the additional ram card... it works... So.. that spoiled all the fun for now 6.8V seems to be good for him. If I go back to 6.5V the system tells that it's going into stop mode after a few seconds (and it does), I guess that voltage is too low for the mac. I don't know if everything else is allr
  17. Hair (yup, still awake..). I read about your 16-18 solution, but I was hesitating. I'll try that one.
  18. Yeah, the logic looks intact. Low power? That could really be the case! About fried stuff I am referring to the power circuitry. I know how these old machines behave with bad digital ICs (repaired two classics and an LC a few years ago), luckily this doesn't seem the case. [Now, that PDF is rather interesting..! I believed Apple Schematics were as real as unicorns or honest people] Anyway, I did the tests, and indeed the voltage drops immediately. It maybe reaches 2V but only for a fraction of a second, it drops to zero in no time. I measured the top left pin of U1M. The second
  19. Further testing revealed something rather interesting: If I discharge C26 and C27 (C25 consequently too), and then start right after powering up (6.5V), the mac actually starts and stays in the boot screen! It shuts down after five to ten seconds. If a hard disk is connected it spins up and dies after one second. The 5V line works fine. Tried afterwards with 6V and it shuts off after like 500ms. Back to 6.5V... same. Techknight, I don't want to stress you with my problems, do you just have an idea about what these caps actually do?
  20. Then probably I did fry some components. I kinda imagined it later on, but it's nice to have your confirmation. Using both pins brings the board to the quasi-initial state, which is: Board off If I give power to the MOLEX connector and then immediately press a button, the computer will turn on for less than a second and then die Successive presses give absolutely no signs of life Even if I disconnect and reconnect the plug and/or reset the PMU. The only way to get it back is to discharge C27, and then it's back again to step 1 This was what the board did before using the single pin (the
  21. Hi everybody I recently obtained from a friend a Macintosh Portable in perfect conditions, and I am currently trying to bring it to life (even if it's useless! Yes, I am wasting my time, got a problem?). It's the very first model, the one with no backlight. First thing first, I disassembled it, and it was a joy. Found immediately a huge leak from the 9V battery, that hurted the logic board underneath a bit. Washed, cleaned with isopropyl alcohol and fully recapped. About the power supply, I am using the lower right connections (the test pads) to deliver about 6.5V with a lab po
  22. Hmmm.... close the topic. I'll answer to myself. IT WORKS! The flyback of the mac classic works on the Plus. Mind that there are multiple models of the classic and classic II, but this one is perfectly identical. No more whine noise.
  23. Hi all I have a mac plus that is making a "zzzz" noise and emits ozone. It's the flyback for sure. What I have is a Macintosh Classic analog board with a quite good flyback that seems almost identical. The marking in the Plus is: 157-0042B Mac Classic: 157-0121 I'm about to desolder them both and test with a tool, but I wanted to ask here if there is a way to be absolutely sure that these two are the same thing (or if anybody already tried). I don't want to burn a card I just repaired. Thank you all
  24. I FIXED IT! You were right I suppose, tried remaking the solder points on the small PCB, tested the transistor.. fine. The potentiometers work outside the board, but apparently they were broken anyway because after turning them many times it actually started displaying with a good brightness!! So I suppose the upper pot was the culprit. I don't have any fluid for cleaning it, do you suggest something? Also I think I spotted the problem with the MLB: the RAM seems defective, the computer powers on fine without it (using the integrated).
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