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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

McIntosh C28 With Bad Transformer
McIntosh C28 With Bad Transformer
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Old 20th November 2012, 05:51 PM   #1
bighodad808 is offline bighodad808
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Default McIntosh C28 With Bad Transformer

I have owned my C28 for about 4 years now but recently had to take it in to my audio tech for repairs. He has diagnosed a bad transformer and states that it needs to either be replaced or re-wound. He told me that to have it rewound, it would cost about $800 and otherwise doesn't know where to find an original transformer to replace it with (None available through McIntosh). This unit is in excellent condition with a perfect faceplate...near museum quality so I would really like to have it repaired but $800 to have the transformer re-wound is more than what the unit is worth. Anyone with any ideas on how to proceed?

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Old 20th November 2012, 05:57 PM   #2
Pano is offline Pano  United States
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McIntosh C28 With Bad Transformer
Moved to analog line level section.
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Old 29th November 2012, 05:55 PM   #3
Ian Finch is offline Ian Finch  Australia
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The options for keeping it original have already be covered by your repairer. Short of someone having a unit with a working transformer that they are prepared to sell as a donor preamp, rewinding is all that's possible, though $800 seems err..inflated.

If you are prepared to fit other parts, the necessary voltages could be supplied by standard transformers that fit in the available space. Only 12-0-12V AC and 5V AC windings are needed from that but a low current, 150V or even a 75V winding transformer (which is likely the blown winding) would be necessary whether the original transformer remains in place or not. That should still be obtainable from any transformer manufacturer in a low enough current rating to keep it small. Alternatively, a complete substitute transformer could be made for less money.
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Old 29th November 2012, 06:13 PM   #4
bighodad808 is offline bighodad808
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Default Economical Transformer Rewinding Service

After not receiving any replies here for several days to my query, I contacted several reputable McIntosh restorers with my problem. Received a very useful referral from Terry DeWick who told me he had a C-28's transformer re-wound by this company last year and that they do quality work. I'll be sending mine to them. $155 to rewind the C-28s transformer. Here is the link :

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Old 30th November 2012, 07:46 PM   #5
techbiker is offline techbiker  United States
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Are you sure that the transformer is the only thing that is bad? It is very unusual for a transformer to die. I have a bunch from decades ago that have been through a ton of stress that are still chugging along happily.

If your transformer is really bad, I would double check everything else in your amplifier because other things are probably broken too. Imagine what would have to happen to damage a solid rod wound with copper... very unusual.
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Old 1st December 2012, 06:30 PM   #6
bighodad808 is offline bighodad808
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Thanks Techbiker,

I'll keep that in mind and make sure that the whole thing is looked at carefully before powering it up with the newly re-wound transformer.

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Old 1st March 2013, 09:11 AM   #7
Petr1951 is offline Petr1951
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I understand the booster transformer is used in auto mode to match the load. If your speakers are 8 ohms or more, then the transformer is probably not necessary. In an extreme case, to increase the load capacity can try to upgrade and install additional output transistors.
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