We have created a power supply interface board for the TS-940S that allows you to use a 28V DIN Rail power supply to provide all of the voltages you need for the TS-940S. We initially called the upgrade the TS Resurrection Upgrade but as we all know, these awesome radios have issues other than the power supplies. It is not the total repair solution for the TS-940S but it will certainly resolve the power supply issues. This new board completely replaces the original AVR Board. There are 5 header cables and a set of 28V wires for the PA you remove when you take out the original power supply and these 5 interface cables plug directly into the new power supply upgrade board. See the Gallery Photos Section.
If you are pretty good with a soldering iron, and have some basic understanding of electronics, you should be able to perform this upgrade pretty easily. Here at our offices, we can normally upgrade a TS-940S power supply in about 1 hour.
There are a couple of videos on our site that you can watch that will explain the entire process. Please keep in mind that the videos are not yet completed and will be changed a bit but watching them now will give you a great understanding of the process.
This upgrade is available now. We made a special purchase and have 260 of the Phoenix 20A supplies in stock for this project with another 250 coming. More information is available in the Kenwood Upgrade Videos Section.
To clear up some questions about the Phoenix supplies and RFI, we have detected no RFI issue at all. They are quiet and really well designed with a failure rate of 500,000 hours between failures!. The model we use is the Quint Phoenix Model 2866776 24 VDC 20 Amp Power Supply. This 24V supply can be easily be adjusted up to 28V and will deliver 20A continuous with boost (additional) current available if you need it. The TS-940S should require 14A @ 28 volts key down if aligned properly which should produce 110 watts. (The TS-940S can be pushed to over 150W but the final stages won't last long if you do!) So this particular supply is perfect for this application. The supply fits perfectly into the TS-940S case with plenty of room for cooling. These supplies are designed to be mounted vertically on a DIN rail but we mount them horizontally in the TS-940S case. They run about 90 degrees F mounted this way which is no problem at all but in order to keep them nice and cool, we also supply a small cooling fan that easily mounts on the original rear panel cover. This small amount of air keeps the supply at room temperature, even while transmitting.
The TS-940S and TS-930 require 28V for the final stage, 21V for the control board, 9V for the LCD display and logic boards, and 5V for the processor and logic. In order to provide these 4 output voltages, the upgrade requires an outboard buck converter for 21 volts. The upgrade board has 2 switching power supplies on board for 9V and 5V. And we are using a 12A buck converter for 21V. Our upgrade board allows you to place the power supply inside of the TS-940S cabinet easily or, you can use any 28V power supply externally.
Feel free to go to the groups.io TS-930 and TS-940 Tech Forum to track some of the problems and solutions that have been found so far.
Let me know your thoughts and thanks for your comments! Jeff AK6OK