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Author Topic: TS-930/TS-940 Power Supply "Crowbar" addition to protect final unit?  (Read 4291 times)
WA1RNE
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« Reply #30 on: November 30, 2017, 10:56:33 AM »


Quote
I did lube the fans yearly and increased the speed of the fan on that more than adequate heat sink.

 Today if a linear power supply were being designed for this application and expected it to pass an FMEA, the heat sink in this radio would not make the cut - especially with the level of protection available to the downstream hardware.

 With all the heavy use I think you've been a lucky guy - or you keep your contesting shack on the cool side.

 ...WA1RNE


 
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WA1RNE
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« Reply #31 on: November 30, 2017, 01:24:11 PM »

 
 By the way, "heavy CW and SSB contesting" still amounts to an intermittent duty cycle versus continuous key down or RTTY.

 Since the operating manual doesn't specify a duty cycle percentage for the transmitter, the power supply should be designed properly for continuous key down operation - which it is not - at least with the heat sink Kenwood chose for the PA DC supply.


 ...WA1RNE
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KM1H
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« Reply #32 on: November 30, 2017, 02:39:06 PM »

Quote
Today if a linear power supply were being designed for this application and expected it to pass an FMEA, the heat sink in this radio would not make the cut - especially with the level of protection available to the downstream hardware.

The 940 goes back to around 1985 and the 930 a few years earlier, long before FMEA was applied to the consumer radios.

Quote
With all the heavy use I think you've been a lucky guy - or you keep your contesting shack on the cool side.

Typical basement with some electric heat used in the winter.

By the way, "heavy CW and SSB contesting" still amounts to an intermittent duty cycle versus continuous key down or RTTY.

 
Quote
Since the operating manual doesn't specify a duty cycle percentage for the transmitter, the power supply should be designed properly for continuous key down operation - which it is not - at least with the heat sink Kenwood chose for the PA DC supply.

The 940 is now on the second station which is used mainly for DXpeditions and light contesting. The other one is on a shelf for backup and gets woke up a few times a year just to keep electrolytics happy.

OTOH it does get regular use as an AM driver into the Alpha 76PA (3 holer) at around 1200W PEP.

None of my rigs are in cramped areas and get plenty of ventilation.
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VE7DQ
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« Reply #33 on: November 30, 2017, 03:13:55 PM »

Every radio is a compromise.

Once upon a time (statute of limitations applies) I accidentally left a '930 transmitting 105W into a dummy load during lunch.  It was keyed up for over an hour before I got back and the heat sinks and transformer were really toasty.  The transformer was starting to smell a bit, but the fans had kept the radio cool enough that it was still outputting 100W when I turned it off.  It took the transformer several hours to make it back to room temperature.

I don't recommend that anyone try this.  Ever.  I had a storage area full of spare Kenwood parts at my disposal, even a transformer.

The power supply and heat sinks in the '930 are adequate for what the radio was designed to do.  Had the radio been designed for 100% duty cycle, it would have weighed a whole bunch more, would have been much more costly and, as a result, wouldn't have sold as well as it did! 
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WA1RNE
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« Reply #34 on: December 01, 2017, 10:30:28 AM »

Quote
The 940 goes back to around 1985 and the 930 a few years earlier, long before FMEA was applied to the consumer radios.

 I'm not sure today's commercial gear does through an FMEA or similar process. But a basic design review for a linear power supply should have caught this blatant issue.


Quote
The power supply and heat sinks in the '930 are adequate for what the radio was designed to do.  Had the radio been designed for 100% duty cycle, it would have weighed a whole bunch more, would have been much more costly and, as a result, wouldn't have sold as well as it did!  

 "Adequate" in the realm of power supplies doesn't give me a warm fuzzy feeling, especially when an expensive portion of the downstream hardware is at risk. Kenwood has designed some really awesome gear but even their stand alone linear power supplies are IMO poorly/cheaply designed, and personally I wouldn't trust them to power my gear.

 The specifications for the 930 and 940 don't specify a duty cycle limitation for the transmitter so one has to assume the duty cycle is 100% over the operating temperature range.

 I don't know what the specifications are for the power transformer, but installation of a heat sink with larger fins will amount to a negligible weight increase.

 Another change I would consider is junking the original fan and modifying that useless perforated fan cover by cutting a round hole in the middle and mounting a modern axial fan right on the back it, then reinstall it on the new heat sink. The original thermistor and control circuit could still be used but the fan will likely be off more than its on with a correctly designed heat sink!

 ...WA1RNE
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KM1H
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« Reply #35 on: December 01, 2017, 01:03:10 PM »

I could see going into Hammy Hambone Hackorama mode if it was actually a real problem.

OTOH by simply speeding up the fan, as I and others regularly did when those rigs were mainline contest competitive, the heat problem disappeared...... .even in RTTY contests where probably 99% ran at lower power since the amps were the real weak link, think Heath, Dentron, Ameritron, etc besides the TL-922 which was the only decent amp Kenwood made and they still have a high resale value.
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WA1RNE
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« Reply #36 on: December 02, 2017, 08:01:09 AM »


 Compared with all the Harbach mods and re-capping that goes on, some of which is probably completely unnecessary (but hey, it's fun), these mods are less Hackorama and more in the realm of peace of mind based on reports of real failures.

 I located a 2005 compendium of 930/940 mods by Jeff King, ZL4AI, where the heat sink temperature was actually measured after making the modification of the fan control circuit to turn the fan on at a lower heat sink temperature.

www.g8wrb.org/data/Kenwood/TS-940S/Kenwood_TS-940S_Fixes_Reviews.pdf


 The heat sink temperature was still 50 degrees C, which translates to a device case temperature of approximately 95 degrees C - at ambient.

 Another words, the efficiency of the heat sink is only 60% of what it should be - and your future operating time with this radio is a testament to the quality and design margin provided by the manufacturer of the power transistors.

...WA1RNE
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N6QWP
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« Reply #37 on: December 04, 2017, 06:51:01 PM »

For the benefit of those who followed along on my quest to find a cure for the power supply problems of the TS-930/TS-940's, I BELEIVE THAT I HAVE FOUND THE SOLUTION!

Tomorrow, in my 940, I am going to do the "new" AK6OK MOD!  After considering all of the various "solutions", I am going  with the replacement Phoenix switching power supply and the new AK60K board that replaces the AVR board.

STAY TUNED FOR UPDATES....I will START ANOTHER STRING tomorrow, devoted just to that modification.....and all that is involved.......and the results.

I am excited, as it appears to SOLVE ALL OF THE ISSUES that have perplexed me in my search for modifying the TS-930/TS-940's power supply.  And, for someone who does not have the knowledge and experience of the contributing Elmers here, it sounds simple, straightforward and foolproof.

It supposedly avoids all of the cataclysmic failures that have ruined so many of these fine old radios.....and that have then required time consuming searches for expensive and hard to find parts, meticulous labor that sometimes involved the unintended devastating slip of a tool when adjusting critical final unit adjustments.....and nerve wracking holding of one's breath when waiting to find out if the mod really worked.

I have also prepared one of my 930's for trying out his yet to be finished board for that rig.  Follow along as I, a less than expert technician, also attempt to bring that one up to more modern standards.

I gave up trying to do the other mods that invariably still left the vulnerable pass transistors and the lethal 40+ vdc lurking.



« Last Edit: December 04, 2017, 07:12:19 PM by N6QWP » Logged
N6QWP
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« Reply #38 on: December 05, 2017, 03:30:33 PM »

Well, it looks like I was a wee bit ahead of schedule.  The latest edition of the AK6OK TS-940 SUPPLY INTERFACE board was not quite ready for release.  It should be ready for "field testing" in a week or so.  

In the mean time, I was able to procure an earlier edition of the board and a smaller 10 amp supply to test out the basic functioning of this modification.  Following is what I found:

Gutting the old supply and AVR board was pretty straightforward and I encountered no problems....other than losing quite a bit of perspiration-due to the anxiety of "butchering" my favorite rig.

Once the dirty deed was done, we started to install the supply, voltage converters, "new" board and fan.  At last, the moment of truth arrived and we hit the power-BUT NOT UNTIL after all of the voltages from the new supply were thoroughly checked out before hooking up to the rig.

To make a long story short....and because this is just a preliminary test before we install the "real" mod-and get the "final results"......EVERYTHING WORKED AS EXPECTED!

The benefits, so far, are:

1)  Waaaay less heat and weight

2)  NO vulnerable Pass Transistors to blow AND.....

3)  NO "deadly" 40+ vdc to ruin the final unit or other circuits in the radio!!!

I'll start the other ''NEW THREAD" detailing how the later edition works, what is required and how it compares with this smaller test version of the AK6OK modification.....as soon as it arrives and I can install it.  

STAY TUNED.......I REALLY BELEIVE THAT THIS IS THE "HOLY GRAIL" OF MODS TO PRESERVE AND PROTECT THESE GREAT OLD RADIOS......AND IT IS SIMPLE TO INSTALL!!!  (No EE degree needed)
« Last Edit: December 05, 2017, 03:51:00 PM by N6QWP » Logged
WA2ISE
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« Reply #39 on: December 06, 2017, 12:12:52 PM »


The benefits, so far, are:

1)  Waaaay less heat and weight

2)  NO vulnerable Pass Transistors to blow AND.....

3)  NO "deadly" 40+ vdc to ruin the final unit or other circuits in the radio!!!


Sounds like the features of a switching power supply, but you'd RFI yourself in receive mode...
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KA5IPF
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« Reply #40 on: December 06, 2017, 12:19:58 PM »

And if it fails instead of 40 volts you could have several hundred and a pile of junk
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N6QWP
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Posts: 256




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« Reply #41 on: December 06, 2017, 01:42:26 PM »

So far, NO RFI DETECTED ON ANY OF THE HAM BANDS.

These Phoenix supplies are built to waaaaay more stringent specs than the original TS-940 one.  Since W3FAC's publishing his mod for the 930 using these supplies, has there ever been, even one reported failure of the supply?

Not that I could find here on the Forums.....BUT NUMEROUS FAILURES OF THE ORIGINAL TS-930 AND TS-940 supplies have failed during that time.....AND, BECAUSE OF AGE, MANY MORE ARE EXPECTED.

I guess there is always the possibility of something failing somewhere......but I am placing my money (and my 930 and my 940) where the odds are the best.  

With a rising failure rate of the old (and NOS, as well) stressed out pass transistors....old fans and the "tight" allowances for tolerances in the supplies of these great old rigs, I'm inclined to go with a much newer design and parts, with wider tolerances and a commercial track record that far outpaces the older design of Kenwood.

Keep in mind, there are now, hardly any old design linear power supplies being incorporated in any of the newer ham rigs--or in commercial applications, as well.

Anyway, these are just my leanings.....from the admittedly little that I know, I want something that is easy to modify, uses the latest and best parts and designs......and that makes more sense to me than trying to doctor up something with a known liability using old "band aids".

That's why they make different flavors of ice cream  ;-)



« Last Edit: December 06, 2017, 01:55:34 PM by N6QWP » Logged
N6QWP
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« Reply #42 on: December 06, 2017, 04:36:01 PM »

Correction--That should read "W3AFC's mod......"
« Last Edit: December 06, 2017, 04:49:48 PM by N6QWP » Logged
N6QWP
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« Reply #43 on: December 06, 2017, 05:50:08 PM »

AS A POSTCRIPT:  According to W3AFC ("who wrote the book" on using the Phoenix power supplies in these older Kenwood radios), there seems to be ABSOLUTELY NO CONCERN OF HUNDREDS OF VOLTS IN THE CASE OF A FAILURE!!!  

According to his research and well known-and published experience with TS-930's-(which apply equally to the TS-940), the MAXIMUM FAILURE PASS-THRU VOLTAGE OF ONE OF THESE SUPPLIES IS ONLY 32 VOLTS!  (Only 3 1/2 volts over Kenwood's designed voltage!).

This is handled MUCH MORE EASILY (than the 40+ failure surge of the original supply) by the final units of both these radios.  ANOTHER REASON FOR USING THIS POWER SUPPLY MOD.

Also, they have designed in RFI limitation circuitry.
« Last Edit: December 06, 2017, 06:14:50 PM by N6QWP » Logged
AK6OK
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« Reply #44 on: December 07, 2017, 07:21:52 AM »

Good morning all!

Thanks to Brad for his comments on this fun subject. I am Jeff AK6OK and our company has been working on this subject and are close to a solution. 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 well 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 cables you remove when you take out the original power supply and these 5 interface cables plug directly into the new power supply upgrade board.

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 should be available within a few weeks - We are waiting for the final PC Boards to arrive. 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 at k6iok.com.

To clear up some questions about the Phoenix supplies, we have detected no RFI issues 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 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 requires 28V for the final stage, 21V for the control board, 9V for the LCD display, and 5V for the processor and logic. In order to provide these 4 output voltages, the upgrade requires an outboard buck converter to produce 21 volts. The upgrade board has 2 switching power supplies on board for 9V and 5V.  As we wrap up the design of this new board, I will be providing more images for you all to review. And we are suggesting a 12A external 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.

And the good news is that we are also working on the same concept for the TS-930S. That new board will also use the same Quint/Phoenix power supply and will be designed specifically for the TS-930 and we estimate it will be available for sale in January.  You will be able to buy the upgrade boards by themselves assembled and tested or, you can buy the entire package including the 20A Supply and external buck converter as long as supplies last. Estimate cost for the assembled board is $170 and the entire package including the 20A power supply will be available for about $330.00. The current retail price for the Quint supply is $445.

Finally, as we see issues in the TS-940S transceivers we work on, we will be eventually be posting all of the issues and fixes on the website at k6iok.com. Let me know your thoughts and thanks for your comments! Jeff AK6OK
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