From a recent discussion on the TS-590 about firmware upgrades, I just got aware of one upgrade, which revised the TS-590SG slow speed startup issue of the cooling fans. With the power supply voltage set to the nominal voltage of 13.8 volts, the cooling fans seem to not start reliable at slow speed, when the TS-590SG gets warm. At one point, when a certain temperature has been reached, the fans kick in at mid-speed suddenly. This affects also the TS-590S. A quick workaround is to set the power supply voltage to something close to 15 volts, which causes the cooling fans to start also at slow speeds, but this is no durable solution and might not be suitable, if other devices are connected to the same power supply, which can’t handle higher voltages than 13.8 volts.

Andy K3WYC wrote a report to Kenwood that suggested low speed fans should be started with a short period of high fan command to ensure they start OK, but he never received any feedback that this proposal had been accepted.

But in June 2020 he wrote this at

It’s now hot in Arizona and I’ve been working 30 m band without my KPA500. Several times low fans have tripped and, each time, there is a short burst of higher speed as the fans start. It seems that Kenwood adopted the high pulse proposal but kept quiet about it.

Frank G0GSR proved the undocumented fan fix was included in firmware version 2.04 for the TS-590S and Gary AC6EG said later, the firmware version 1.05 for the TS-590SG was released on the very same date.

So these are the firmware versions, which included the fan fix:

TS-590SG: Firmware 1.05 (release date January 30, 2019)
TS-590S : Firmware 2.04 (release date January 30, 2019)

In the Worked All Germany Contest 2020 I noticed the same, Andy K3WYC has already observed during this summer. After about 15 minutes of running CQ with a decent rate at 100 W, the fans started at low speed with a short high speed burst first. The case temperature after long CQ runs with the latest firmware version is definitely lower than in previous contest participations with firmware version 1.04, which I had on my TS-590SG until last week. So every TS-590S and TS-590SG owner, who’s into contesting or has in general high TX duty cycles, should have installed at least the above mentioned firmware versions. If you don’t have it, install the lastest version. As of now (Oct 2020) they are:

TS-590SG: Firmware 1.07 (release date March 12, 2020)
TS-590S : Firmware 2.05 (release date March 12, 2020)

The TS-590SG firmware can be found here. The TS-590S firmware can be found here.

It’s great to see Kenwood fixing issues found out and reported by the customers, but I don’t really understand, why they are just not able to mention this in the firmware release notes. At least that this issue has been fixed is worth a note, even if Kenwood don’t like to mention it has been reported by a loyal customer instead of being found out by their own engineers. Kenwood still has to learn much about customer relationship …

My most profound thanks go to Andy K3WYC, Gary AC6EG and Frank G0GSR.