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RodCastler

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  1. RodCastler

    Mac classic blows MOSFET

    Similar issue, and yes: same board: 630-0560-240V.
  2. RodCastler

    Mac classic blows MOSFET

    Not sure which type of connector you're referring to but I can tell you that mine looks like this: http://www.nightfallcrew.com/wp-content/gallery/swapping-crt-tube-apple-macintosh-classic-se30/20150724_083127.jpg
  3. RodCastler

    Boot Floppy for Powerbook 145

    That helped, thank you. Although the images I could find were non-bootable ones. The only bootable image I could find for System 7 was in http://www.emaculation.com/doku.php/basilisk_ii Thank you!!
  4. RodCastler

    Boot Floppy for Powerbook 145

    Hi, the hard drive on my powerbook just died. I was hoping to boot it from floppy but I can't seem to find a System 7 image to boot it with. Any ideas where I can download it from? I have a system 6 image but of course the 145 spits it out complaining about the release not being compatible to its taste. Many thanks in advance, Rod
  5. RodCastler

    Mac classic blows MOSFET

    Another Mac has been liberated! Symptom was: Low voltages at the 5v and 12v rail. When under load, the rails went all the way down to 4v and 9.9v respectively. Cure: Re-capped every electrolytic, replaced TDA4605, CP23, IFBC40 and CY17G (4N36 used as replacement). Thank you so much for your help!!
  6. RodCastler

    Mac classic blows MOSFET

    Thank you for such a comprehensive reply, apm. Yes, I had check the voltage and it is close to 300V and everything seems correctly set-up for a 220v machine. Actually the previous state of this mac was that it could remain powered for ever but would show garbage on screen and the HDD would not spin (low voltages). I double checked the components you suggested and CP23 would be the only one out of spec. I have not found a local store that carries a replacement. As soon as I get my hands on a new 270pF capacitor will let you know. (I'll have to replace the mosfet and the driver as well, but I have found those). Thanks!
  7. RodCastler

    Mac classic blows MOSFET

    I am re-testing some components. CP23 reads 560pF on the multimeter. It's a 271J, should read 270pF. This is a new suspect. I removed it and the oscilloscope shows a strange behavior when under a square wave, like it's open circuit. It's clearly NOT shorted. Assuming it's defective (maybe open or heavily out of spec), could this cap be the responsible of the MOSFET being fried? I'll try to replace it with something else and will let you know.
  8. RodCastler

    Mac classic blows MOSFET

    Hi all, Thanks to the valuable material found on these forums I have been able to *almost* liberate my mac classic. Looking for the source of the voltage drop at both 12V and 5V rails, I began with the routinary full re-cap of the leaky ones. Finally, after replacing the mosfet, the mosfet driver, the opto-isolator and *every* electrolytic cap, I was able to get rock-solid voltages from the power supply, and the machine booted from the HDD with a sharp and great-looking image on screen. Happy Mac! The problem now is that after almost a minute into the boot sequence, boom!: fuse blown and I could measure right away that the MOSFET got dead shorted. After the event, - I've looked for shorts in the transformer and it all looks good. - I Measured for shorts coming from any potential solder bridge or shorted diode, but all looks good. - DP7 and DP5 measure OK although they are both identical (which I'm not sure if it's correct) and also differ from the models stated on some other forum threads. They may have been replaced previously although I didn't see any signs of previous intervention on the AB. I trust them even though one shows signs of overheating on the exterior. - I've tested every cap including ceramic and boxed ones: No shorts. - Rectifier, transformers they all measure okay. - Mosfet measures fine when compared to some spares I have although I'll replace it along the mosfet anyways. What should I look for? What might be frying the MOSFET? I can't seem to find signs of overload on the circuit. I have been unable to find a replacement for CP23, DP7 and DP5. They are my current suspects but with no real reason: They all test functional. * RP1 surgistor launched a small high-voltage arc on one of its sides that actually burned the surface, but still works. Haven't been able to find a replacement for it either. This arc might be a sign of something wrong. Has happened only twice, right on power on. Thank you so much in advance for any help you could provide, My board is a 220v, but almost identical to this one:
  9. RodCastler

    Macintosh Classic (one) Analog Board Trouble

    Thanks! Actually the optocoupler is the very first thing I replaced after the re-cap. I used a 4n36 since I'll have to wait a few months before the exact part makes it to where I live: no local stores carry such part. I wonder if a 4n36 is at least a good replacement for testing purposes...
  10. RodCastler

    Macintosh Classic (one) Analog Board Trouble

    I'm running out of suspects. All of the resistors and remaining caps measure OK, as well as the diodes, the voltage regulator and several other main components. ... and I still have the voltage-out of spec issue, that drops under load. This is measured without the motherboard installed. Today I performed a test: While powered with the defective smps, I artificially injected +5 and +12 to the board and my friend wakes up with a VERY wobbly and noisy screen. Next step: "Classic Mac Repair Notes" mentions a crowbar SCR Q8 that I will check tomorrow, although I don't think the issue is there.
  11. RodCastler

    Macintosh Classic (one) Analog Board Trouble

    Hi there, Please allow me to join you since I'm on a similar situation with a mac classic and I'm currently troubleshooting the analog board as well. Symptom: 5 volt line reads 5.00v but drops to 4.1v under 1A load. 12 volt line reads 11.54v and drops to 9.47 under 1A load. (I'm using an electronic load for testing. Using the Hard Drive as a load doesn't drop the voltage that much but is surely not enough to even spin the drive) HDD was tested to be OK on another mac. What I have done: - I have recapped the suggested CP line (after which, power-up time went down from 80 seconds to 3 seconds. This was the original symptom). - Large 200v cap measures spot on. - I have already tested the mosfet to be not-shorted. - Temporarily replaced a suspect optocoupler (with a 4n36) but results won't vary. - Diodes measure OK. Next step: Measure every resistor in the RP line as suggested above. Any other suggestions?
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