Denon AVC-3800

This Denon AVC-3800 A/V amplifier was listed on ebay as 'faulty no sound output' however it did power up. So i made the seller an offer and secured the amp for £20. These Denon amplifiers are superbly built and heavily fused so i was hoping that a quick fuse change would solve the problem. Well obviously that would have been way too easy!

After checking all the fuses and having a good poke around with the multimeter i discovered that one of the 2 main transformers only had a voltage output on one of it's secondaries. It's the transformer the top of which you can see to the left in the picture.

Once the transformer was removed i discovered that one of the secondary windings was open circuit. I managed to find an service manual for the amp online, it had detailed schematics so i was able to work out what the secondary voltages should be. Problem is these transformers were almost certainly specially made for Denon, howvever the output voltages were not anything unusual. So i decided to see if i could replace the conventional transformer with 2 toroidal transformer with the right secondary voltages. Electrically i was sure it would work fine, the question was could i fit the 2 toroidal transfomers in the space vacated by the U/S original transformer?

The answer was yes, just! If you look carefully you can see the second toridal transformer underneath the first one. So does it work? Yes, it sounds superb, the toroidal transformers were not cheap as they have fairly high VA ratings but it still works out that i got an awful lot of amplifier for the money.

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