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Thread: Silver and gold Apple IIe power supplies blowing the transformer

  1. #1

    Default Silver and gold Apple IIe power supplies blowing the transformer

    Hi there, I've had two IIe power supplies (a gold one and a silver one) go on two different machines which were both in storage since the early 90s. The failure mode is the same in both - the supplies work and power the machine successfully but after a short while (20s in one case, 60 mins in another), the transformer lightly catches fire, producing a paper burning smell. In both cases I've powered down the machine within seconds.

    I haven't been able to find much about this failure mode. Has anyone else seen this? I have one more IIe supply that I dare not use for fear of the same thing occurring. It also doesn't look like this is a standard component - does anyone have a source for them? I'd love to repair them if possible. I'm willing to buy the reactivemicro kits to rebuild them but I'd rather keep them original if possible.

    JH

  2. #2
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    Transformers don't normally have a shelf life, so if they are just seemingly going up in flames for no reason they are being overloaded or overdriven.
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  3. #3
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    Are you sure its the transformer and not the filter caps? have you opened the psu and can you share some photos? This all sounds very odd. I have worked on a lot of Apple II and IIgs power supplies. Never once has a transformer given me issue let alone caught fire.

  4. #4

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    Burnt paper smell sounds like those nasty RFI input line filters. The transformers are switchers and don't usually have that much paper in them. Those filters produce lots of smoke and burnt paper smell.
    Dwight

  5. #5

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    I guess the OP is using like synonyms transformer and power supply...

  6. #6

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    Quote Originally Posted by george View Post
    I guess the OP is using like synonyms transformer and power supply...
    If it is the RFI filters, open the supply up and cut the RFI filters out. They provide little function purpose. They do offer some protection from line spikes but not much. You can replace them with new ones but I'll admit, I've not bothered to do it. The supply may emit more RFI to things like radio receivers and TV that still use antennas.
    They were made with a plastic case that shrinks over time. It then cracks open and lets moisture in. This causes the paper insulation to become leaky. The last one I had go took about 3 hours before letting out its smoke.
    You can do a search for post on the proper type of replacement to use. The new ones will last a little longer as they are in better cases. They come in two types, I forget which is which. Capacitance value is not to critical but the voltage is.
    Dwight

  7. #7
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    Quote Originally Posted by Dwight Elvey View Post
    If it is the RFI filters, open the supply up and cut the RFI filters out. They provide little function purpose. They do offer some protection from line spikes but not much. You can replace them with new ones but I'll admit, I've not bothered to do it. The supply may emit more RFI to things like radio receivers and TV that still use antennas.
    They were made with a plastic case that shrinks over time. It then cracks open and lets moisture in. This causes the paper insulation to become leaky. The last one I had go took about 3 hours before letting out its smoke.
    You can do a search for post on the proper type of replacement to use. The new ones will last a little longer as they are in better cases. They come in two types, I forget which is which. Capacitance value is not to critical but the voltage is.
    Dwight
    Thanks Dwight, I had no idea thats why they cracked over time. I have heard that you dont have to replace them, but I usually do. They are pretty cheap when bought in bulk.

  8. #8

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    Quote Originally Posted by VERAULT View Post
    Are you sure its the transformer and not the filter caps? have you opened the psu and can you share some photos? This all sounds very odd. I have worked on a lot of Apple II and IIgs power supplies. Never once has a transformer given me issue let alone caught fire.
    It looks like it may just have been the filter caps after all, C1 is definitely cracked. I'm going to cut it out and see if it works. I saw this transformer and was sure it was cooked, but I guess that's just the way the coating looks. Thank you for the guidance! transformer2.jpg

  9. #9
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    I got my first (untested - for parts/not working) Apple II yesterday. - Within 10 seconds of power up the RIFA filter caps cracked and gave off the paper burning smell smoke puff. I was quite happy to let it continue to run. Now that the cap has given up the ghost it no longer smells. I'll probably get around to replacing it at some point - as Dwight mentioned, they are not important for core PSU function.

    My machine now works perfectly.
    It came with a floppy drive but without software. I love the ability to bootstrap it from a mobile phone connected to the cassette audio input and create a new DOS boot floppy.

  10. #10
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    Quote Originally Posted by JonathanHunt View Post
    It looks like it may just have been the filter caps after all, C1 is definitely cracked. I'm going to cut it out and see if it works. I saw this transformer and was sure it was cooked, but I guess that's just the way the coating looks. Thank you for the guidance! transformer2.jpg
    Now thats just the proper enamel coating. It looks fine. Im sure its just the filter caps.

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