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Kenwood KT-3300D FM Stereo Super-Tuner Service & Alignment

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.

Super Tuner

The Kenwood KT-3300D is an FM stereo tuner from 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.

Alignment

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 hand 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.

Results

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 80’s.

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.

From the outside, the KT-3300D is fairly nondescript, typically 80’s Kenwood in terms of styling.
However, this hides a really serious heart – the KT-3300D is a very advanced tuner, with complex distortion cancelling circuitry and an advanced detector and discriminator circuit.
Five-gang front end, in copper screening box

Some of the many, interacting distortion-cancelling adjustments
Power supply rectification and filtering
Here’s the potted transformer. This runs HOT, suggesting it is perhaps marginally rated for this application.
The ‘brains’ of the unit – an LSI capable of tuning LW, MW and FM bands, complete with PLL and control circuits
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Starting the alignment process, with some band-edge measurement and adjustment
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Working on tuners, you simply must use a proper set of alignment tools like these. Anything else will likely wreck the delicate ferrite slugs inside the inductors of any tuner.
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You also need a high-quality, low distortion FM signal generator, like my Panasonic VP-8175A. Here, I am outputting a 98MHz test signal into the KT-3300D.
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You also need to be able to accurately measure distortion of the signal output by the tuner. Anything else is guesswork and forget trying to do something like this ‘by ear’. It’s impossible, and I mean actually impossible, like time travel at this point. Here, I am using my trusty Tektronix A501 distortion analyser. This shows the incredibly low 0.0178% distortion on a mono test signal – very impressive, perhaps the best I’ve seen.
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And of course, you have to have the service manual if you are ever going to be able to figure out what each adjustment does, let alone the correct way to perform all 25 adjustments.
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Finished Kenwood duo – KT-3300D and D-3300P