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Customer Comments

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Being the designer of the Kenwood TS Series upgrade kits, it can sometimes be a tough task to keep up with it all. The TS-940 kits went through 5 different revisions before we released it as a product. Getting parts, scheduling assembly, testing each and every one and just making sure that everything comes together is challenging. 


Receiving your comments just makes my job easier! It gives me direction when we have made something not quite as easy as it should be. And it is truly satisfying to see these radios put back into service. Thank you for your encouragement! I will continue to share your thoughts to give others the courage to give it all a try! Jeff AK6OK

From Craig, W3CRR

Hello Jeff, I just made my first SSB and CW contacts with my "new and improved" TS-940SAT "Plus" and am a happy guy. The power supply upgrade went very smoothly thanks to your terrific kit, instructions and videos. After installing the power supply and upgrade board, I mounted the included power supply fan inside the back "vent panel" behind the now discarded heat sink. It's running off one of the two 9-volt auxiliary outputs on your upgrade board. The other 9-volt line runs directly to the 940's PA fan for continuous cooling per your recommendation. I simply detached the appropriate small shielded cable feeding the fan and spliced the 9-volt lead from your board into it. (For those who wish to replicate this mod, the PA fan power cable is located on terminal 6 of the LPF board near the bottom right hand side as viewed from the rear. The "block" on which the final amp board and fan assembly are mounted must be removed from the rear of the transceiver to access the LPF board, but that's an easy job). I am extremely pleased with the results of your very worthwhile upgrade, Jeff. As you promised, the rig now operates in a perfect room-temperature-cool and welcome worry-free manner, even during a lengthy CW ragchew QSO. As a bonus, I'm getting about ten additional "feel good" watts output. This, I figure, is probably due to a lack of voltage/current "sag" in transmit mode thanks to the new and better power supply components. So, Jeff, here's my endorsement: "I encourage all TS-930/940 fans to invest in this easy-to-accomplish and actually enjoyable power supply upgrade project. Sure, you'll be a little nervous as you cut away the old wiring and toss the attached components but, trust me, follow the written instructions and video presentations and all will be well. In fact, your fine old Kenwood will be better than ever. VY 73, Craig, W3CRR

Ralph NA6D

I have had both my TS 930 and 940 receive the power supply mod. Instead of the wicked heat put out by the stock power supply, both rigs now run cool. The heat sink is room temperature even running the rigs all day! Once the stock power supply gives out, it’s likely to blow out the finals, which are no longer available. I recommend Jeff’s P/S without reservation! 

Ralph, NA6D

From Tom Goodfellow (WU6Q)

 You folks have done a tremendous job .....fantastic design .....I've owned two 940's and rebuilt the AVR board but it's still a poor approach ....I have several radios .... probably my favorate is the Yaesu FT-1000D .... but my 'daily' working radio is the 940. I have an additional fan blowing on the back of the PS to assist in keeping it cool. I have one question, does the PS fan run continuously ? I assume so ....I understand a 12Vdc fan running with 9Vdc but is it necessary to stay cool ? I understand the horizontal mounting issue, could it have a temp 'sensor' like the original 940 design to only come on as needed. I do 80 percent listening to 20 percent transmitting ....and QRP type CW late at night ...really don't want to hear a fan going (that's one draw back in the FT-1000, although I have modifed it to run as needed at lower RPM and kick up when necessary). Thank you and I looking forward to scrapping up the dough to get the PS ....73 

From K6GHR

This is just a short note to say THANK YOU SO MUCH for making the TS-930 & 940 upgrade kits a reality. I've visit W3AFC's website, I have two 776 Quint Power Supply but I was scared to take the plunge. I own a TS-930 and a TS-940. The 930 runs great, the 940 is sick with power supply problems. You're the first to show how to upgrade the 940's power supply. After reading the instructions and watching your videos, it's almost plug and play. I will order the 940 upgrade kit in a couple of days. When the 940 is up and running again, I will upgrade the 930 as well. Once again, Thanks for your time and Let's resurrect some radios! Cheers & 73, Gwendolyn - K6GRH

From KD4LYH

Its about time someone stepped up to the plate . Theres alot of 930s Kenwoods with blown finals because of the original supply failing. I wonder if the finals can be found or a substitute. Perhaps a tutorial added to your website on replacing the bad finals . Great job on the upgrades for these radios.

From John - W3AFC - Check him out at w3afc.com

If you need to rebuild your Kenwood TS-930S power supply, but you don't want want to modify your old AVR board, you can buy a ready made kit from Jeff Hilliard of Compudigital that will simplify the process for you. The kit has a replacement AVR board that eliminates the need for the various sub-voltage regulators, resistors, Zener diodes, and even the 5-watt PA current sense resistor. For $199, you get a BRAND NEW 20/26-amp Phoenix Contact Quint, the AVR/power board, and electrical and mounting hardware. The board contains circuitry to provide all the necessary voltages, reduced-voltage fan outputs, and the Ic and Vc voltages for the IcA and IcB  ("sense") circuit. Trust me, it's worth it.


I'll provide many more photos and information in my write-up. And yes, there IS a glow from the top when the radio is on. But it looks cool and works great. And the glow serves as a diagnostic light. But you might not see it because your radio will run so cool that you will be able to stack other radios, external antenna tuners, or even magazines on top. 

NOTE: My 930S has been on all day for the NAQP contest, and it's STONE COLD. No heat whatsoever. As in zero!

From WA4ZYN

Hey, Jeff!   I just soldered in the LED upgrade for the subdisplay of my TS-940S.  Lookin’ great!  Sure is an improvement over that murky green color.   Thank you so much for the upgrade. 73, Tnx agn. Francis WA4ZYN

From Jamie - VK3PKY

Good Morning Jeff, mate just to advise the TS 940S power supply upgrade arrived safely, and packaged perfectly. Great work by you and your company.


Ok, installation was a breeze, followed your information via the online Compudigital video’s, thanks for that, a great initiative. Initial testing confirmed all voltages were set perfectly, but I did have 1 issue that I had me scratching my head and wondering if the radio had suffered some damage after the existing supply had expired,,,,,, when powered up after the conversion was done, the radio clock display was oscillating at 1 second intervals changing from displayed time to displayed ATU ready, really weird, also Audio was dropping out in tempo with the display change.


After some thought, I remembered that while I had the radio on the bench, preparing for the delivery of the upgrade, I replaced the clock battery, then I remembered reading about the reset switch, behind the clock, any way carefully lowered the front panel, and hit the reset, bingo oscillation stopped, thank God.


Once radio was tested and all functions operating, it was time to have a go at the PLL unlock, and replace the second battery at the same time.


Got the PLL board out, and discovered the foam block, removed the block, got to work on the bottom of the board where the foam block had attached itself to the tracks, spent 2 hours removing the garbage from the traces, re soldering dodgy soldering, and upon completion, the radio now initiates from switch on with the PLL unlock now history.


Well done to your company on giving us all an opportunity to “resurrect” these radios.

I have two 930SAT’s that I will be changing out the old supply’s as well. I hate the feeling of trepidation every time I switch on or off these radios, the Upgrades will let me enjoy usage of these great radios once again.

Kind Regards,

Jamie Frencham.

VK3PKY

What is this project all about?

Kenwood TS-940/TS-930 Supply Upgrade Project

After being a Ham for over 50 years, I have finally decided that one of the best transceivers ever made is the Kenwood TS-940. One of the biggest problems with the TS-940 has been the power supply. The supply on a working radio can tend to run at very high temperatures even in receive mode. 


Compudigital Industries has designed a full power supply upgrade that is  available now for purchase. We have finished the final testing on the TS-940 Supply upgrade and plan to release the TS-930 upgrade and make it available as well. The replacement of the supply allows the radio to run at room temperature instead of self destructing because the supply is so hot! 


To see videos regarding the upgrades, click on the Videos button at the top of the page.

Jeff - AK6OK

Big Schematics

Ham Radio schematics are really tough to follow, especially when our old eyes can't quite follow small lines on the page like we used to. If you are a Collins kind of guy, Compudigital has a full line of large schematics for most Collins models. You can check out our site at www.bigschematics.com to see what we have so far to offer! We will soon be producing large schematics for the entire Kenwood radio line as well. 


One of the unique additions we have made to the Collins schematics is color annotation. Our team has added different colors to the different signal paths allowing you to easily follow signals through the diagram. If the demand is 


If you would like to see a diagram that we do not offer, please contact me using the Send a Message link below.


West Coast Swap Service LIVE!

The West Coast Swap Service happens almost every weekend on 7.240Mhz covering Northern California at 12:30PM PST. You can listen to the swap live by clicking on the link above. soon, you will be able to email your listings into the swap administrator and your listing will be read live here on this site. The world of the West Coast Swap Service has just gotten a bit bigger!


The receiver for the Swap Net is in Auburn, California and the antenna is a 540 foot loop. The receiver is a TS-940S that has been modified with the new 20A switching power supply and interface kit  that is being sold on this site. 

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TS-940 Supply Upgrade - FAQ

NEW TS-940S Supply Upgrade Board

How much current does a TS-940 need?

In extensive testing using the TS0940 upgrade board, the radio requires 28V @ 14A, 21V @ 1.5A, 9V@ 250ma, and 5V at under 1A. The 28V supply is used exclusively for the final output stage. The switching power supply should be able to supply 28V @ about 15A peak. 

When is the upgrade for the TS-940 going to be ready?

The latest board is working perfectly and will be ready to ship by 2-1-2018. You can order the boards now. Use the Order Now link above to place your order.

Can I use an external power supply for the TS-940?

Yes! - Using just our supply upgrade board and a single buck converter for 21V, you can use your external 28V supply to run your TS-940. The board will be available as a kit and assembled so you can use your own 28V external power supply to run the radio.

Are we building a supply upgrade for the TS-930?

Yes! We are in development on the TS-930 supply upgrade board at this time and will be entering the testing stages in a few weeks. That process take about 30-45 days and then we should begin production. 

Why are these internal power supplies such a problem?

The original TS-940 uses a linear power supply that outputs 28V, 21V, 10V, and 5V. The power transformer and bridge output combination starts with almost 40 volts which feeds all of the other circuits to drop the various voltages accordingly. When you start with 40 volts and drop it to 28V at 14A, things are going to get hot. The TS-940 can easily run 150 degrees when in receive mode. And when you transmit, it will get hotter. These excessive temps cause component failures. A shorted power supply pass transistor can easily destroy all of the boards in the radio. This supply upgrade normally runs at room temperature and can prevent a future catastrophic failure.

What is the supply upgrade for the TS-940 going to cost?

The Quint 20A power supplies retail at over $400. We have made a special purchase of 250 supplies and will be offering a New Quint supply and upgrade board assembled and tested for around $300. If you wish to use your own external power supply, the Board alone with all components and cables assembled will be sold for about $165. The store is online now and we are accepting new orders.. 

What we have learned about the TS-940

The Kenwood TS-940 is the best HF radio ever made!

The receiver is amazing, and the transmitter puts out more power than your average transceiver these days. It our testing, we can hear signals as low as .05 microvolts! I have never seen a radio that can perform that well. The design is amazing based on the age of the radio. But new technologies allow us to replace the power supply with a much more efficient option. The new Quint Phoenix switching power supplies have very little noise and an expected life of 500,000 hours. There are other power supplies and other brands that will work just fine as well. But the Quint supply fits perfectly within the case and leaves plenty of room to install an interface board to wrap the project up easily. 

There are a few common issues with the TS-940

Common issues include:

1. A complete power supply failure which can damage the entire radio. 

2. A shorted output transistor in the original power supply puts up to 40V through the entire radio and can render it useless. 

3. Low output power is common and much of the time caused by an RF output driver transistor that is no longer available. 

4. A faulty attenuator resistor commonly shows up when the receiver hears better when the attenuation control is in the -10db or -20db range instead of the 0db selection. 

5. The display produces dots instead of the normal frequency displayed numbers.

6. When you turn on the radio, the only thing that happens is the LCD backlight comes on.

7. The radio is completely dead... We love this problem. Might just have a dead power supply!

8. There are some modifications that can be made to enhance the receiver

9. The soldering technology back then was pretty bad and many of the problems today can be associated with cold solder joints. 

Can these common problems be solved?

Most of these problems can be resolved by a technician with the proper tools,  test equipment, and of course the knowledge. There might be hams in your area that have the ability to make these repairs as well. As a part of the services we plan to provide, we will be posting not only these issues but also will be providing links to other sites that address these issues with some clarity.