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Thread: Tried repairing mac classic analogue board but now its blowing fuses

  1. #11

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    There is a difference on the schematic not shown for 220V compared to 110V. The 220V would use a capacitor rated for about 450V while the 110V would be two capacitors of 250V as shown in the schematic.
    You are running 220V is my first question? If your line is 110V it will blow the switcher transistor. Also, make sure the line voltage does not drop too low. When I was in the Azores, at night the line voltage would drop to about 160V. That much under voltage will often blow the switching transistor. These power supplies are not happy with under voltage.
    I'm looking at your two original pictures. The optical isolator looks different. It is hard to tell if it is just a lighting difference or possibly it is upside down.
    Dwight
    Last edited by Dwight Elvey; August 10th, 2020 at 07:37 AM.

  2. #12
    Join Date
    Apr 2020
    Location
    Belfast, Northern Ireland
    Posts
    33

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    Dwight, I'm in the UK so its 230v. Our voltages are stable (well generally run about 236 up to about 248 dependant on region). Interesting comment on Azores with voltage fluctuating so wildly down to 160V, I assume their normal domestic supply is 230. Don't suppose you know how they generate electricity at Azores being in the middle of the Atlantic, Solar or Hydro? I'm sure it would be a fantastic place to visit though.

    I replaced the optical isolator when reassembling the board. I had read its one component liable to failure from spilt electrolytic so thought it would be worth doing while at it. Its an equal package according to the site I ordered it from. I still have the old part, perhaps I should just reuse it.

  3. #13

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    Quote Originally Posted by Glen M View Post
    Dwight, I'm in the UK so its 230v. Our voltages are stable (well generally run about 236 up to about 248 dependant on region). Interesting comment on Azores with voltage fluctuating so wildly down to 160V, I assume their normal domestic supply is 230. Don't suppose you know how they generate electricity at Azores being in the middle of the Atlantic, Solar or Hydro? I'm sure it would be a fantastic place to visit though.

    I replaced the optical isolator when reassembling the board. I had read its one component liable to failure from spilt electrolytic so thought it would be worth doing while at it. Its an equal package according to the site I ordered it from. I still have the old part, perhaps I should just reuse it.
    I was there in the early 1970s. I'm sure things have changed since then. I orders a couple 12V CT transformers and used them as boost auto transformers. I then used a Variac to fine tune. It worked well with my HiFi. I was in the Navy while there. It was a little crazy. The air force ran most of the ground logistics, the navy flew most of the planes and the army ran the boats in the habor.
    Dwight

  4. #14
    Join Date
    Apr 2020
    Location
    Belfast, Northern Ireland
    Posts
    33

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    Well the new components arrived today (DP2 and QP2) fitted switched on and... its working 100%. Nice solid 5V and 11.7v which I suppose might be a bit low but that could be the lack of load on the 12v rail.

    Time to get it in the machine and fingers crossed it boots.

    Much thanks for the help guys.

  5. #15

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    Quote Originally Posted by Glen M View Post
    Time to get it in the machine and fingers crossed it boots.
    ....
    And?????

    Enquiring minds want to know!!!!

  6. #16
    Join Date
    Apr 2020
    Location
    Belfast, Northern Ireland
    Posts
    33

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    Quote Originally Posted by desiv View Post
    ....
    And?????

    Enquiring minds want to know!!!!
    Sorry, I should have updated this.

    Yep she fired up straight away and booted off the old HDD all be it, its not making nice noises and occasionally throws an error so I think its on its way out. The drive is full of the last owners documents some of which are dated 2018 so it wasn't that long ago that this system was someones presumed main computer.

  7. #17

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    Set it up to boot from ROM and forget about the hard disk. Most games you can run on it will fit a single floppy disk anyway.

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