Author's Description:

Kenwood KX-990SR is perhaps the rarest deck from the series that included many models – from KX440, through 660, 770, and 880, to the top model KX1100. Certainly, over the years, KX880 in all its iterations was the most popular.

This model was produced from 1985 to 1987, and the nomenclature was chosen quite high for a dual-head, auto-reverse deck – i.e., KX990 SR was positioned between KX880 and KX1100. Realistically, the whole series looks like peas in a pod, and 990 SR represents KX880 with added options. It cost around 450 EUR (900 DEM), about 100 DEM more than the KX-880G, for example, which was not little at all – for around 1,000 DEM you could get a good three-head deck, for example, the Technics RS-M253X, which even had a dBX expander.

The build quality is very good, it hides a very good three-motor mechanism, and the recording/playback head is amorphous. To remind you, an amorphous head material should have a lifespan about five times longer than ordinary permalloy heads. There are also two displays, as seen in my earlier descriptions of KX-880 and 1100. The KX-990 SR deck is quite slim, and the two displays represent a truly intelligent and useful solution: the horizontal one for operational status even shows when the deck is rewinding in either direction, it has a real-time counter, the tape type is displayed, Dolby status, track search, etc. Truly comprehensive, I would say. Additional options include index display of tracks, cassette space search, and some others, for which Kenwood was a specialist, obtained by a combination of buttons, e.g., during playback, if you hold down the play button and press the rewind button, the deck will rewind to the beginning of the tape, but then start fast forwarding to the first track and continue playback from there.

One thing I don’t like about the whole series is the overly simple recording initiation – pressing the Rec button next to the rewind button, of the same size and shape, just slightly apart. Pressing the wrong button or accidental press will activate erasure and recording of new material, which can be disastrous if the cassette has already been recorded and intended for playback only, without the recording tab removed.

But that’s just a minor issue. Let me get back to the description: the peaks of the KX-990 SR are some of the most beautiful and practical for my eyes that I have ever encountered – it’s nice that Kenwood didn’t skimp on that at all.

Probably, when Kenwood created this deck, they targeted consumers who weren’t passionately involved in recording, so they omitted to include bias and sensitivity controls for tape response, as on some versions of the KX-880. A real shame.

Another interesting thing is the front transport control keyboard, slightly slanted at the bottom, everything is made properly, but it was taken from other models and reconfigured because of the additional reverse playback button. In fact, the wide stop button that stands in the lower row on other decks in the series is divided into three buttons here, two for playback, while the Play button, which was above on other models, has now become the Stop button. Here’s an example in the pictures:

The result is one unused button, between the playback buttons. Kenwood decided to duplicate the Stop button, so although unmarked, this button in the middle of the lower row has exactly the same function as the upper one, which has a regular Stop label. In fact, this deck has one large Stop button in two parts.

Technical description:

The Kenwood KX-990SR is essentially an 880 model in one of the poorer versions, without dynamic bias, later HX Pro, TLLE, and other delights, but the basic electronics are almost identical.

The power section is elaborate and fair, the boards are similar, it is clear that the same team developed both decks.

The mechanism is auto-reverse, with three motors and basically the same as on the KX-880 and KX-1100, but with a conventional DC motor instead of direct drive… what a shame, it would have been almost perfect… but maybe Sankyo as a supplier didn’t offer that option.

What fascinates are the massive flywheels with traces of additional balancing. Each of them would be more than enough for an ordinary one-way deck, and these two together really look more than enough. The transport itself is sturdy, strong, and more than capable – if you compare it with, for example, the Technics RS-BX501 model from the last series, you’ll see what I’m talking about – the Technics transport looks like a child compared to the one in Kenwood.

Service:

The deck came to me with working transport functions but produced no sound output nor did the meters show any signal, although they were obviously turned on. Going through the schematic, I first suspected the Dolby circuit power or the line amplifier right after the input because the meters didn’t light up even during playback, and more importantly, not even during pause.

When I opened it up, the deck looked in good condition, but removing the cover left me speechless: soldering everywhere, printed lines marked with markers, glue residues, and damaged traces… there was everything. The technician who tried to repair the deck before me obviously struggled, even suspected that the problem might be with the glue becoming conductive… the deck looked so bad that I simply thought it wasn’t worth fixing.

Also, some solder joints were terrible:

First, I removed the remnants of removed glue and markers from the board to have a better view, and then just in case, I went through all the joints that the previous technician refreshed. This did not yield any positive result other than my confidence in the solder joints being okay.

Then I started to follow the input signal with an oscilloscope: the line amplifier had both input and output and sent the signal from the front panel all the way to the back, to the board with the Dolby B/C circuits. The Dolby ICs had input but no output, and there could be several reasons for that, but usually, the power supply is checked first. It turned out that one of the two voltages (+/- 7.6 V) was missing, the negative one, -7.6 V. Fortunately, I had the service manual and found that this voltage is created from a stabilized 10 V supply, which was present. At first, I suspected an 8.2 V zener diode, found a similar one, but the result was the same. Checking the capacitor connected in parallel showed that it had partially shorted. I had checked it earlier, but the buzzer on my instrument works up to about 20-30 ohms, and the resistance of the capacitor was a fixed 44 ohms and it didn’t trigger it. I replaced that tiny electrolytic capacitor, the -7.6 V voltage appeared, and I got a signal and sound output.

Although it sounds simple, it took me about 5 hours of work. Here’s the problematic electrolytic capacitor in the picture – C8:

The second problem that arose was that the deck refused to record in reverse mode, i.e., when the tape moves in the opposite direction. It simply refused to activate recording, so I thought there might be some problem with the recording protection switch, but everything was fine. I spent more time and found one damaged trace, due to glue removal, so I repaired it and… nothing. I was puzzled about what was happening, so I started to trace the recording protection communication lines on the board and… I saw something. Someone (the previous technician?) completely severed a jumper on the board, so that from the side of the components it looked as if it had never been there, while from the bottom side, the pins were sticking out neatly and everything looked fine. Why did they do that? I have no idea. Why didn’t they just cut it, so they could solder it back later? I don’t know.

Anyway, since there was no jumper, the processor couldn’t receive a signal through the switch that everything was okay and recording could be done on the cassette. I put in a new jumper and solved the problem.

That took me a few more hours, although it was a minor thing, and the deck recorded properly on one side, and I could set it fixed to always record on the other side regardless of whether the cassette had a recording tab or not, I didn’t want to give up.

The mechanism was mostly untouched, but there were also some bad things there: the belt had been replaced but the grease at the bottom of the flywheels had become sticky and stuck one of the copper flat springs that the flywheel shaft had eaten over time, see in the picture:

Fortunately, I had the same one in the parts collection, I disassembled everything, washed, additionally cleaned, and lubricated. As I had to disassemble the right flywheel to remove it, I also cleaned and lubricated the so-called mode switch.

By the way, one wire from the multipin connector broke off, probably weakened from previous repairs, so I repaired that too.

In the end, the deck worked properly. Adjustments using the test cassette and software were minimal, and it functioned completely normally, with a response up to 17 kHz on a normal tape (TDK D).

Just in case, I replaced about 9 capacitors around two larger resistors because the resistors surely heated them. I put in others with a higher maximum voltage and working temperature up to 105°C.

I must admit that I am glad to have breathed new life into this device.

Sound:

The KX-990SR model is a good deck, with a sound that has a lot of detail in the high frequencies and generally maintains the neutral stamp that Kenwood decks from those generations had. It’s not terribly dynamic, nor transparent, nor extremely detailed, but it’s simply honest and just what you’d expect from an upper-middle-range auto-reverse deck in terms of sound.

The recordings it makes are more than acceptable for cassette enthusiasts. With a KX-880D or HX version, you’ll get more information in the high frequencies using even cheap normal tapes, besides, they also have variable bias adjustment. However, the KX-990SR is such that you won’t be ashamed of it, with stable sound and good compatibility compared to recordings made on other machines.

Switching to chrome (more precisely pseudo-chrome) TDK SA90 cassette gave a clearly better result primarily in cleaner, more transparent, and detailed sound, even better than I expected.

Conclusion:

A rare, fairly unknown, well-made deck, primarily good for cassette enthusiasts who have an old collection they’d like to listen to without flutter and other annoyances, but with the ability to make a decent recording if needed.

I would add that if I were to choose for myself an inexpensive but quality combination, maybe the Kenwood KX-880 in one of the versions, intended for recording, and the KX-990SR model intended for playback, would be one of the better combinations.

Excluding the Nakamichi Dragon and TEAC R999X, I also have an interesting older Sansui auto-reverse deck in my collection that has been sitting for years: D-770R. I’m really curious to see how it will sound compared to the Kenwood.

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