The PA module for this radio became faulty, and it turned out to be a relatively easy fix thanks for some Google searches.
It turns out that on some early radios Kenwood was somewhat prone to not putting any thermal transfer compound between the PA block and the heat-sink. This meant that the PA device would heat up beyond specification and over time the substrate would start to deform with the heat. This meant that the PCB tracks could crack, which is what happened to my unit.
I wasn’t able to take any pictures of the actual crack as it was so small I needed a magnifier to see it, but it was there. Soldering over the track where it had broken created a bridge that was ample to restore the radio to full working condition. The photos here show what needs to be done, but it was certainly worth half an hour in my time vs. buying a replacement radio or PA block.
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- The PA block is at the rear under the metal can.
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- Uncovered ready for removal. 2 screws and 4 pins to de-solder.
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- Remove the PA block, this is shown after heat-sink compound was added.
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- The plastic cover pops off the block quite easily, you can see the individual components.
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- One of these tracks had a hairline fracture, a magnifier and multi-meter were used to find it. Once repaired the radio returned to normal operation.