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  1. #1
    Kevin Caulfield's Avatar
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    Enlarger transformer repair Melbourne

    I recently bought a Durst L1200 colour enlarger. The TRA 450 transformer didn't work at first. It had a 5A fuse instead of a 2.5A fuse. I checked the inside and made sure it was set to 240 V and replaced the fuse with a 2.5 A one. It then worked, at least for a little while but blew the fuse after several on/off cycles. I have since gone through several more fuses in the same manner. These are ceramic fuses which I found at Jaycar.

    Can somebody please suggest a repair place where they would be able to check out the transformer to work out why it keeps blowing fuses?

    Thanks for your help.

  2. #2
    polyglot's Avatar
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    Make sure you use a slow-blow fuse. A fast-blow fuse on the primary of a transformer will be destroyed by inrush current, as you've found.

    Edit: you don't need ceramic (sand-filled) fuses for this application, that's total overkill in terms of blocking. They're meant for use with hugely inductive loads and high-power applications, e.g. where the fault-current might be much larger than the operational current. The idea is that the gas in a glass fuse can form a plasma but that sand will not. Edit 2: ceramic fuses are not slow-blow, therefore they *will* fail early.
    Last edited by polyglot; 02-06-2012 at 01:32 AM. Click to view previous post history.

  3. #3
    Steve Smith's Avatar
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    As Polyglot says, use a slow blow fuse. These are usually marked with a 'T' (for time) so you need one marked 'T2.5A'.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  4. #4
    Kevin Caulfield's Avatar
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    Thanks, guys. I'll try a slow-blow fuse in the next day or two and will report back.

  5. #5
    polyglot's Avatar
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    Also easily recognised because they tend to contain a spring-like heatsink instead of just a tiny tiny straight wire.

    Quote Originally Posted by Steve Smith View Post
    As Polyglot says, use a slow blow fuse. These are usually marked with a 'T' (for time) so you need one marked 'T2.5A'.

    Steve.

  6. #6

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    There are three versions of that unit, post a pic of the inside and I can probably email you a circuit diagram for it.
    Bob

  7. #7

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    I have had a voltage stabiliser(Devere 504) repaired expertly in the Croydon area recently. Very happy with the service. If you want I can let you know the business name.

  8. #8
    Kevin Caulfield's Avatar
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    Thanks for the posts. I bought some slow-blow fuses today and will give them a go later today. They are actually ceramic like the other ones, but this time they are marked "T 2.5A", so they should be fine. I checked the other ones and they were "F" instead of "T".



 

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