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Thread: Apple ii europlus

  1. #1
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    Default Apple ii europlus

    Well, might have taken on a bit. Not only have I just got a TRS-80 model 4 ive not been brave enough to switch on, I have just received an Apple II europlus that needs a bit of tender care.

    Opened up the PSU for an inspection and its decorated with capacitor remains ! so some work before I even turn it on.

    Anyone have a good circuit diagram for the PSU

  2. #2
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    post pictures of the damage!

  3. #3
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  4. #4
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    Quote Originally Posted by VERAULT View Post
    post pictures of the damage!
    Will do, working night shift this week though, so will be awhile

  5. #5
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    Quote Originally Posted by Gary C View Post
    Will do, working night shift this week though, so will be awhile
    A recap will solve most problems on the apple2 supplies. The other common problems can be quickly found with a multimeter.

  6. #6
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    Quote Originally Posted by David_M View Post
    A recap will solve most problems on the apple2 supplies. The other common problems can be quickly found with a multimeter.
    The failure of C6 was enough not only to blow the 2.5A fuse but to actually crack the glass ! (never seen that before)

    Recap is in order but where to get them.

    Found an apple spec that lists the 47F caps as +100% / -10% and they seem hard to find in the correct format. Have some nichicon 47F caps on order of the correct mechanical spec and electrical spec other than a tollerance of 20% (and ESR is a bit marginal on another spec i found, but thats not listed in the apple spec)

    Anyone have a source ?

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  8. #8
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    The capacitor that blew isn't the rifa cap that normally blows without killing the fuse

    The one that blew is not critical and doesn't need to be low ESR simply increasing the max voltage rating will give a lower ESR.
    I typically replace the mains filter caps with ones from ebay rated at 400v.
    Just like these ones
    https://www.ebay.com.au/itm/5PC-47uF...AAAOSwomVbFQlP

    Because it was a mains filter cap that blew and took out the fuse due to a short it might have taken out the bridge rectifier also, so check that with your multimeter before you power it up again.
    As I said none of the caps are critical for value, rather than the expense of paying for low ESR I just use higher voltage rated caps to get the lower ESR with a larger safety margin. The output filter caps can all be 1000uF 25v and it will work fine.
    The only one that needs the correct value is C7 and I generally replace that with a 220uF 16v cap.

    You can get away with using the higher voltage rating because modern capacitors are smaller than their 80's counterparts.

  9. #9
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    Got some 400v caps with the advantage that they are virtually the same size and colour as the originals, also got a replacement c7 at 25v on the way, but need to get a new fuse. Looks like a T2.5 20mm ? (as the glass had split, the cap pinged out of the holder and sailed into the deeper recesses of the garage) and have lots of those at work.

    Rectifier seems ok on a quick check, though is showing a short N to neg, which the diagram is showing a cap across, so prob need to leave the fluke on for longer for a true reading.

    Think the previous owner must have recently turned it on, cap blew and flogged it on cheap to me as each of the big caps were wet underneath so didn't look like it had been long since the failure.

  10. #10
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    Quote Originally Posted by Gary C View Post
    Got some 400v caps with the advantage that they are virtually the same size and colour as the originals, also got a replacement c7 at 25v on the way, but need to get a new fuse. Looks like a T2.5 20mm ? (as the glass had split, the cap pinged out of the holder and sailed into the deeper recesses of the garage) and have lots of those at work.

    Rectifier seems ok on a quick check, though is showing a short N to neg, which the diagram is showing a cap across, so prob need to leave the fluke on for longer for a true reading.

    Think the previous owner must have recently turned it on, cap blew and flogged it on cheap to me as each of the big caps were wet underneath so didn't look like it had been long since the failure.
    From memory its a 2.5A fuse.. all my apply parts are currently packed in a box somewhere (moving house soon).

    Pull the bridge and test it out of circuit. Your multimeter will just charge/discharge the caps so you wont get a valid read on it in circuit.

    Yes, its not uncommon. People pull them from storage with the intention to sell them as a working machine, so the first thing they do is plug them in and turn them on, which of course is when the caps are most likely to blow.
    They don't realise old capacitors degrade when not used and need to be powered up slowly with a variac to recondition them. I'm too impatient for that though, plus its cheaper for me to recap than it is to buy a variac.

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