Comments on the Kenwood TS-590S Transceiver

Robert Stampfli / KD8WK — November 2011
Kenwood TS-590S HF Transceiver
The Kenwood TS-590S HF Transceiver

In 2011 had the opportunity to acquire a Kenwood TS-590S transceiver. This rig has generated high acclaim in ham radio circles, and for good reasons. It has an excellent receiver with tons of bells and whistles, mated with a superb human interface.

It's Hard to list all the TS-590S's Positives

Before I get into the particulars, I have to confess that I'm a Kenwood fan, and have been since I got my ticket back in the mid-1980s. My first rig was a Kenwood TS-430S. (A quarter century later, I still have that rig, and still enjoy operating it.) Thus, from the start, the TS-590 just seemed to fit me like a glove.

Kenwood has shown remarkable restraint over the years with changing the human and external interfaces on its rigs. When I unboxed the 590, I simply unplugged all the cables from my 430 and plugged them into the 590 and I was up and running. It all just worked. (Well, almost, as will be explained below.)

Kenwood has spent a lot of time over the years perfecting the ergonomics on its ham gear and it shows. The controls are well placed and their operation makes logical sense. The switch gear (buttons and knobs) on the rig exude quality in both look and feel — let's hope they are as good on the 590 as they were on my 430, where after a quarter century not one switch or pot has malfunctioned or become intermittent. Furthermore, the TS-590S is a handsome rig.

Most controls on the 590 are dual-function: Pressing a button quickly controls one function, whereas pressing-and-holding it causes some other action, usually related to the first. All the front-panel pots are dual-concentric.

Other plusses:

Kenwood TS-590S HF Transceiver
The Kenwood TS-590S HF Transceiver — Back Panel

Using the TS-590S with a Computer

With the increasing popularity of digital communications, Kenwood has paid close attention to the TS-590's computer interfaces. Yes, two are provided: a conventional (and increasingly dated in today's world) serial port, and a USB port. The USB port is the more useful of the two, presenting both a virtual control port and a built-in sound card to the computer. What this means is that no external box or other cables are required to use the digital modes on the TS-590. Just load Kenwood's virtual port software and the digital software of your choice onto your PC, connect a USB cable to the rig, and you're good to go. The serial port may be used for rig control only. (Either may be used to update the TS-590's firmware.) One neat feature: Both the real serial port and the virtual device that the USB presents may be used simultaneously to control the rig. Thus, you can run Kenwood's control program concurrently with an independent digital communications suite without the need for any "glue" software.

I've used the Fldigi program with the TS-590, and it works well. For control of the rig, I have not ventured beyond using Kenwood's own ARCP-590 software. The ARCP-590 does the job quite competently, although it can be made to lock-up under Windows XP and Windows 7 by invoking the right sequence of events. But avoid these uncommon sequences and you find that the ARCP-590 software provides a very nice interface to the rig.

I especially like the ARCP-590's software bandscope. Like the real-time equivalents found in some rigs, this software scans the band and produces a display of the signal intensity it finds, graphed against frequency, but the rig is not otherwise usable while the scan is in progress. However, simply clicking on some portion of the readout will cause the 590 to jump to that frequency. It's quite efficient for finding nearby conversations. Some may claim the 590's lack of IF output for an external panadapter is a liability, but consider: One of the rig's main selling points is its two-stage down-conversion superhet design, with excellent roofing filtering on the very front end for close in signal rejection. In this environment, it would seem a panadapter interface would require it's own dedicated IF chain to produce anything usable and that would add cost with no other value. The built-in bandscopes found on other rigs may be a useful novelty, but they do come at the price of limiting where the designer can place the roofing filters.

Dealing with Electret Mics

One problem I encountered with my new TS-590 occurred when I tried to interface a headset containing an electret mic to the rig. Electrets require a small DC voltage to work, and the 590 (like other Kenwood rigs) conveniently supplies 8V on one of the mic connector pins. The interface is straight-forward, and I had several laying around that I had built for other Kenwood rigs. However, when I attempted to use one of them, which, incidentally, had been working just fine on my TS-430, it sounded terrible over the air — like RF was getting into the mic — and the VOX would consistently false-trigger. Fortunately, W1AEX has come up with a workaround, which consists of adding a bypass capacitor to the Vcc line. Using 1/8 watt resistors and a bit of legerdemain, I was able to construct this interface on the back of of an 8-pin mic plug, allowing it to be completely self-contained within the shell of the plug once assembled. I did not include W1AEX's pre-emphasis network in what I built, electing instead to use the 590's speech processor which by design adds emphasis to the highs. With his electret circuit (sans pre-emphasis network) combined with a $20 GE headset with boom mic from Walmart (product code 38974), and running the processor with a PRO.I setting of 25 and a PRO.O setting of 55, I have had people who know me say that I sound just like I do in person. And VOX operation is velvety smooth. It remains a mystery to me why the additional bypass capacitor is required with the 590, but adding it does completely resolve the issues with using an electret mic.

Power Overshoot Problems

Unfortunately, the TS-590S, like a distressingly high number of modern ham transceivers, exhibits symptoms of power overshoot that can cause problems with some power amplifiers, in particular solid-state amps which are the most sensitive to short power spikes. The degree of power overshoot seems to vary from unit to unit. On my PEP wattmeters, I definitely see some power spikes on the leading edges of my transmissions. It would take a scope to quantify them precisely, but my best guess is that amount of overshoot in my rig is around 3db. (And, in all honesty, I own other rigs which are worse in this regard.) My TS-590 does not exhibit enough of an overshoot to affect its operations with my primary amp, an AL-80B, which by the way is a good amp to use with rigs exhibiting this problem, since it is capable of absorbing up to 100W of input power without damage.

Some 590 owners claim that allowing the amp to provide ALC feedback helps to mitigate the problem, and fine tuning the CAR control may help on CW. Others have gone so far as to build an attenuator pad for their rigs. Kenwood has issued a firmware patch which partially addresses this problem and stated that this is all they intend to do. However, rumors continue to circulate that a more comprehensive hardware fix will eventually be forthcoming.

Problems with SMD Fuses

The TS-590S contains several internal fuses designed to contain the damage in the event of a fault. However, rather than using conventional user-replaceable fuses, in some cases the Kenwood engineers elected to use SMD fuses — surface-mounted devices — which require specialized equipment to replace. One such fuse, F901, has proven itself particularly problematic, opening for no apparent reason. The symptom is sudden loss of audio on receive. In an internal poll conducted in 2011 in the TS-590S Yahoogroup, about 10% of those responding indicated they had experienced an F901 failure in their TS-590. Most of these failures were seen in units manufactured in October, 2010 (serial number B0A...). A few owners have managed to replace the SMD fuse themselves or tack another fuse across the blown device, but this procedure is not for the faint of heart and most have elected to return their rig to Kenwood for repair. Interestingly, earlier TS-590s do not seem to exhibit this problem, leading some to speculate that Kenwood received a batch of bad fuses. Starting in November, 2010, Kenwood substituted a .500 amp fuse, denoted by the letter 'F' stamped on the SMD part, for the original .375 amp component (denoted by the letter 'E'). This change was made in the 590 production line and in units which came back for repair with a blown F901, and it appears to resolve the problem.

Some Other Nits with the TS-590

Here are some other things about the TS-590S I find annoying. Bear in mind, though, that Kenwood is still actively updating the TS-590S's firmware, both to fix bugs and in response to the input it receives from the TS-590S user community, so view this list a somewhat fluid.

Failed Finals!

After two and a half years of use, the MOSFET finals in my TS-590 suddenly bit the dust. I was operating in a contest, using the 590 to excite an AL-80B amp when the power output dropped to nearly zero and I received reports that my signal had suddenly "dropped 30db and become distorted". Investigation revealed the 590, as opposed to the amp or the antenna, to be a fault. The problem occurred while I was at the mic and I observed no other anomalies at the time — no pops, sizzles, changes in SWR, or other indication of a problem.

The 590 has two MOSFET power output transistors arranged in a push-pull configuration. One of these probably failed, taking the other with it. These transistors are not cheap, but I have never heard of another 590 failing this way.

The rig was sent to Kenwood East for repairs. They confirmed the finals were blown and quoted $164.80 for a replacement pair. They also diagnosed a bad T/R relay ($10.61). They upgraded the infamous F901 fuse ($1.01 for the part) (see above) while they had my unit open on the bench, although the original had never failed. Finally, they installed the latest firmware. The labor charge was $195. Adding the two-way shipping brought the total cost to around $455. All told, the rig was out of commission for about 7 weeks while we waited for the backordered MOSFETs and relay to arrive, but the final results were good: My TS-590 is now back in service and performs as competently as it did before the fault.

When something like this happens, it of course makes one wonder what provoked the failure in the first place. Kenwood East thought that the problem was externally induced. However, the amp never showed any indication of a problem, either at the time of the failure or afterwards, and continued to work well with my backup rig, and now with my newly repaired 590. I was operating everything in the configuration I normally use, except that I was on 75 meters when it failed, a band I rarely use. I tend to believe that the failed T/R relay was somehow the culprit, although I cannot explain why the protection circuitry didn't protect the finals. Some people have speculated that the odd duty cycle of the fans in this rig (see above) may have provoked the failure. A short poll of other 590 owners I know revealed that their TS-590s do not exhibit the this behavior. However, I find it difficult to believe that this alone would be sufficient to cause the finals to overheat. In any event, I hope there are no latent gremlins left in the rig, awaiting the opportunity to pounce once again.

TS-590 Owners Net

There is a 40-meter HF net for TS-590 owners which meets every Wednesday evening. The most current information about the time and frequency for this net, along with any special skeds, may be found at http://groups.yahoo.com/group/TS-590Net/.

Conclusions

No rig is perfect in all situations, but the Kenwood TS-590S is an excellent performer that presents enormous value at its price point in the $1500 range. It outperforms competing rigs that cost several times its price. It has a comfortable human interface and a receiver that can compete with the best of today's rigs. If it can live up to the reliability of its predecessors, it would appear Kenwood has another winner here!