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"Repairing a Kenwood KA3700 Amplifier That Produces No Sound (di Vincenzo75)

 

Got a vintage Kenwood KA3700 amplifier that powers on but produces no sound? In this article, a fellow electronics enthusiast walks us through the steps they took to diagnose and fix the issue. A practical guide for anyone looking to bring their old hi-fi system back to life with some patience and a bit of troubleshooting.

Appliance:
Kenwood KA3700 Amplifier

Issue:
The amplifier only displayed a red LED light and did not perform any functions.

Repair:
Upon opening the cover, I immediately noticed discoloured resistors, with one completely burnt out. I began by replacing R17, R39, R18, and two C1827 audio output transistors. However, when I tested the amplifier, the two audio output transistors burned out again, and the resistors started to smoke.
I restarted the process and discovered that the CI318 transistor was also short-circuited. After replacing it, I tested the amplifier again, and it worked perfectly.

Kenwood KA3700 amplifier detail of changed components

Kenwood KA3700 amplifier internal detail

Thank you
Vincenzo75.

Warning!

The advice and instructions provided on this site come from hobbyists rather than professional technicians, meaning there is no guarantee that they are accurate or represent the best solution.
Additionally, using the tools and techniques described here should be done with careful consideration of one’s own abilities.
These articles assume that the tasks will be performed by individuals with the necessary skills and knowledge to use the required tools safely, without risking harm to themselves, others, or property.
Therefore, the owners of this site cannot be held responsible for any direct or indirect damages resulting from the application of the content found here.
Before undertaking any DIY activity, it is strongly recommended to read the Safety Notice, which provide a basic (though non-exhaustive) list of precautions to follow.

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