A customer recently asked me to service and align his latest acquisition – a stunning Kenwood KT-3300D FM analogue stereo tuner.
Due to other repair commitments, it took me longer than I would have liked to get to this gorgeous KT-3300D. The wait was worth it though. As you’ll see, aligning a tuner like this is time-consuming but critically important.
The Kenwood KT-3300D is an FM stereo tuner from the end of the golden age of engineering in Japan. The KT-3300D is what many refer to as a ‘super-tuner’. This is because of its very high specs – distortion is vanishingly low and sensitivity and separation are very high. The tuner is capable of distortion down below 0.01% in mono, and only a little more than that on stereo signals – astonishing figures.
This particular KT-3300D, like most older tuners, was not performing optimally. Distortion was very high on test signals, up around 1%, which is unacceptable. The only way to restore the performance was to perform a complete RF alignment. Luckily, my customer is a smart guy and likes to own the service manuals for his equipment. True to form, Terry had tracked down an original hard-copy service manual and this made the alignment process easier.
Aligning a tuner is often a challenging job and a tuner this complex, with this much sensitive circuitry was one of the biggest alignments I’ve ever done. The KT-3300D has a five-gang front end and some tricky distortion-cancelling circuits to align, plus several pilot-cancelling stages, adding up to around 25 adjustments in total – each one different from the one before. This is alignment madness and it took me two complete runs through the process to get distortion down to a level I was happy with, and to get the sensitivity up to a satisfactory level.
Of course, you don’t just need the service manual and some time to align a beast of a tuner like this – you need a selection of premium test and measurement equipment and the right tools to be able to successfully work on a tuner like this one. Just to align the front lend for example, you need a set of proper radio alignment hand tools or you will certainly break fragile ferrite cores. Then you need a low-distortion signal generator, distortion analyzer, cables, impedance adapters and more.
In the end, though, the hard work and dedicated test equipment paid off. I was able to reduce distortion down to a tiny 0.0178% in mono, a truly excellent result. I was not able to get the stereo distortion down as low as the specs said was possible, but specifications were often a little ‘optimistic’ during the 80s.
This was still an improvement of epic proportions, given the high 1% original distortion! You can read more about how one KT-3300D performed in one of the legendary ‘shootouts‘ performed by the Tuner Information Center.