Date   

Re: K3 Locked Up - MCU LD

Joe, KO8V
 

When that is selected I've had problems with it causing an instantiation of a serial mouse. Then the system thinks it has two mice. From then on random mouse inputs start happening.  Then the real mouse on the computer acts up. I was just thinking that that could also be causing problems going the other way and possibly causing the OP's problem.

I've seen the recommendation in more than one place to turn that off as well as disabling modem control on start up.  In some ways FTDI is still in the dark ages with their driver.  Better than others, but could be improved upon.  


BTW, this is on a Windows system.  Other OSes are ok

--
73
Joe, KO8V


Re: K3 Locked Up - MCU LD

Gordon LaPoint
 

Joe,
    Not sure why you have the problem with "serial enumeration" on FTDI based devices.  I have used them, on multiple computers, with multiple operating systems, and have never had to "turn off" the serial enumeration.  I have had to change the comport number on occasion, but that is about all the "adjustments" I have ever had to do the the FTDI com port setup.
Gordon - N1MGO

On 11/24/2020 7:09 AM, Joe, KO8V wrote:
If the USB converter is an FTDI based device, be sure serial enumeration is not set.  The setting is in the advanced area of the driver properties for the com port.

It's something FTDI continues to turn on be default in their driver, even though there are probably only "two" serial mice left in the entire world. When's the last time any one saw one in the wild? I really wish they would change the driver to drop it.  It's hassle to have to turn it off for every new com port created by the FTDI driver.

--
73
Joe, KO8V



Re: K3 Locked Up - MCU LD

Joe, KO8V
 

If the USB converter is an FTDI based device, be sure serial enumeration is not set.  The setting is in the advanced area of the driver properties for the com port.

It's something FTDI continues to turn on be default in their driver, even though there are probably only "two" serial mice left in the entire world. When's the last time any one saw one in the wild? I really wish they would change the driver to drop it.  It's hassle to have to turn it off for every new com port created by the FTDI driver.

--
73
Joe, KO8V


Re: command available to switch on/off internal ATU?

DL1AKP OM Andy
 

Hello Joe,

thanks so much! That's great. Exactly what I need.
73, Andy


Re: [Elecraft_K3] Momentary RX quieting when transitioning from TX to RX, but only sometimes...

Brian K0DTJ
 

Elecraft uses pin diode T/R switching. There’s no relay. I’d suspect a loose coax connector or marginally failed coax as the culprit. GL!

Brian, K0DTJ

On Nov 23, 2020, at 12:59, Randall K Martin <rkmassoc@...> wrote:

This is a very old topic, but it is the closest match to my problem. One of my K-3's is not returning to full RX after transmitting. I am a contester, and this behavior showed up this past weekend in ARRL SS SSB. It happened earlier this year, but only for a brief time. This weekend, it became consistent. I don't think the amp is the culprit, because if I tap gently on the K-3, the receive signal comes back. If I don't transmit on that K-3 for a while, the problem goes away. Might be heat related in some way.

I don't have a schematic, but assume there is a sealed T/R relay that I need replace. Has anyone in the group done this particular surgery, or do I need to send it to Elecraft?

73 Randy K0EU


KX-3 and Yaesu FTDM-100 channel lockup

Larry
 

My KX-3 sits in a metal rack next to a Yaesu FTDM-100.  Common 12V power
supply.  I noticed that when the KX-3 was turned on the Yaesu locked up
on one of my UHF channels.  Didn't make any difference what band the
KX-3 was on nor the frequency it was tuned to, it locked up the Yaesu on
just one UHF channel.  The KX3 isn't my primary radio so it's usually
turned off.  Hard to tell what the mixing scheme is in the Yaesu but
wouldn't have thought there would that strong a signal of some sort
coming out of the KX3.

Larry W0OGH


K3S MIC Problem

Bill Rogers W3UL
 

I'm guessing that I'm not the first to notice this on the K3S.  I don't do much SSB but was active in Sweepstakes this past weekend and noted that occasionally the audio would go dead.  Looking around I found that the MIC gain had dropped from the usual (about 16) down to zero.  I placed a toroid around the MIC cable and this seemed to prevent the problem most (but not all) of the time.  The MIC cable (and the K3S) both sit next to an Alpha 87A amp.  I don't recall reading about this phenomenon.  Is some protective function being activated?     

--
73,
William (Bill) Rogers / W3UL
Annapolis, Maryland U.S.A.


Re: [Elecraft_K3] Momentary RX quieting when transitioning from TX to RX, but only sometimes...

Randall K Martin
 

This is a very old topic, but it is the closest match to my problem. One of my K-3's is not returning to full RX after transmitting. I am a contester, and this behavior showed up this past weekend in ARRL SS SSB. It happened earlier this year, but only for a brief time. This weekend, it became consistent. I don't think the amp is the culprit, because if I tap gently on the K-3, the receive signal comes back. If I don't transmit on that K-3 for a while, the problem goes away. Might be heat related in some way.

I don't have a schematic, but assume there is a sealed T/R relay that I need replace. Has anyone in the group done this particular surgery, or do I need to send it to Elecraft?

73 Randy K0EU


Re: KIO3B question

Ken K6MR
 

Hi Keith:

 

I’ve only ever done a couple of BGAs.  It is tricky, but the small ones are doable.  If you make sure the ball size is consistent before you start it usually works.  I have the board on a rotatable platform, so I can preheat the board from underneath, then place the device and heat if from above.  Most of this SMD work requires practice.  If you watch Louis Rossman on his YouTube channel, he does all kinds of stuff on Apple boards without a problem.  But he’s been doing it a long time.  Just another one of those things we need to learn how to do with the new technology.  I’m a firm believer in “If you can’t fix it you don’t own it.”.

 

These are the first two boards I’ve looked at.  I don’t have them in my K3s but someone asked if anyone wanted to look at them so I volunteered.  Very nice layout, and I’m sure glad you folks labeled most everything with the top silkscreen.  Circuit is easy to follow, so hopefully it will be straight forward.  Whatever hit the USB line on these two really did some damage.  Strange since you do have an ESD protection device next to the USB connector.  It might be as W4TV notes that there was a problem with bonding of the radios and it was a difference in chassis voltage levels that caused it. 

 

Ken K6MR

 

From: Keith_WE6R
Sent: Monday, November 23, 2020 10:30
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] KIO3B question

 

Hi Ken, I think that micro USB is for "future use".
Are you able to change U11, that is the hard one. It has to float on with heat.
Keith 

 


Re: KIO3B question

Keith_WE6R
 

Hi Ken, I think that micro USB is for "future use".
Are you able to change U11, that is the hard one. It has to float on with heat.
Keith 


Re: K3 Locked Up - MCU LD

Jim
 

Thanks Keith
P3 works perfectly so does Kenwood for rig control using the same converter.
I will check the chokes after this weekend and drop you an email.  No rush as I am working single band this weekend using the K3s
Thanks again
Jim


Re: K3/Ø (not mini) For Sale

K5OT
 

The K3/Ø is sold.  Thanks for the interest and bandwidth!

73,
Larry K5OT


Re: [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

KE1F Lou
 

Did you have the enclosure ground connected to the common station ground? I did that and I have no noise issue at all from the PS.

73, Lou KE1F

On 11/21/2020 4:21 PM, Everett N4CY via groups.io wrote:
Hey Bob,

While you are talking about Astron power supplies I was making some repairs on mine and discovered the B- was bonded to the case. I removed the ground as having the B- grounded can and will cause a ground loop. I noticed after the ground was removed that it dropped my noise from S5 to S2. 

My Astron has meters and both meter lights were blown, so I drilled a 1/8” holes in the tops and places some very small LED lights in the top of the meters. I then used a 1.5k resister in series with the LEDs. Now I have lighted meters again. 

Everett N4CY

On Nov 21, 2020, at 2:59 PM, Bob McGraw - K4TAX <rmcgraw@...> wrote:

As indicated on my K3S:  RX  14.3V @ 1.25A      TX  100 watts output 13.9V @ 17.6A   The supply is an Astron SS-30M, the power cable is ~36" of Red/Black #10 zip cord. Connections are crimped and soldered at both ends.   

Also, I have a dedicated ground conductor #10 AWG between the ground terminal on the radio and the ground terminal on the power supply. {I find this to be very important with every radio I've used and owned.}

73
Bob, K4TAX


Re: [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

Everett N4CY
 

Hey Bob,

While you are talking about Astron power supplies I was making some repairs on mine and discovered the B- was bonded to the case. I removed the ground as having the B- grounded can and will cause a ground loop. I noticed after the ground was removed that it dropped my noise from S5 to S2. 

My Astron has meters and both meter lights were blown, so I drilled a 1/8” holes in the tops and places some very small LED lights in the top of the meters. I then used a 1.5k resister in series with the LEDs. Now I have lighted meters again. 

Everett N4CY

On Nov 21, 2020, at 2:59 PM, Bob McGraw - K4TAX <rmcgraw@...> wrote:

As indicated on my K3S:  RX  14.3V @ 1.25A      TX  100 watts output 13.9V @ 17.6A   The supply is an Astron SS-30M, the power cable is ~36" of Red/Black #10 zip cord. Connections are crimped and soldered at both ends.   

Also, I have a dedicated ground conductor #10 AWG between the ground terminal on the radio and the ground terminal on the power supply. {I find this to be very important with every radio I've used and owned.}

73
Bob, K4TAX


Re: Shipping a KPA500 to factory.

Bob McGraw - K4TAX
 

"Why are repairs required?  This is expensive equipment.  Bad design should be covered by recall and re-engineering."   
You'll need to contact a higher power or authority to have lightning damage and lightning surges explained and prevented.    No, this is NOT expensive equipment as and used as a hobby.   Why does it fail?  From experience, it is largely operator error or poor installation practice.   Neither of these are covered by the warranty.   Although I find Elecraft to be very generous in that regard.  

As to shipping, I've used USPS Priority Mail which I find to be less expensive and much faster than UPS or Fed-X.  I view the longer it is in transit, the more likely it is to be damaged.   I shipped my K3S from TN to CA using the original Elecraft box and packing.   It was shipped on Wednesday they received it on Friday.   Of course, your travel time may vary. 
For now, and it is getting worse, shipping times are extending.  If I needed to ship my K3S, KPA500, or such to Watsonsville, I think I'd wait until mid-January. 

73
Bob, K4TAX


Re: [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

Bob McGraw - K4TAX
 

As indicated on my K3S:  RX  14.3V @ 1.25A      TX  100 watts output 13.9V @ 17.6A   The supply is an Astron SS-30M, the power cable is ~36" of Red/Black #10 zip cord. Connections are crimped and soldered at both ends.   

Also, I have a dedicated ground conductor #10 AWG between the ground terminal on the radio and the ground terminal on the power supply. {I find this to be very important with every radio I've used and owned.}

73
Bob, K4TAX


Re: P3 Questions

Robert W5AJ
 

and K1ESE

The P3 Utility allows you to save P3 configuration, just like K3 Utility program

I use that (and K3 Utility) to save K3 and P3 configuration on arrival at Rental site…

Works

Worthwhile to have backup

 

73 W5AJ

 

PS:  K3 are still humming along here, all fine.

I use LP-Pan and the wonderful Built-in waterfall/bandmap of writelog

https://writelog.com/elecraft-k3-sdr-setup#more-2196

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Al N1AL
Sent: Saturday, November 21, 2020 12:38 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] P3 Questions

 

The waterfall is updated at the rate of the spectrum display update.  So if you slow down the display update using the "Rate" command it will slow down the waterfall speed as well.

Alan N1AL

On 11/21/2020 8:47 AM, John Huffman wrote:

I have a 'new to me' P3 (no P3SVGA) and have a couple of questions.

 

Is it possible to slow the speed of the waterfall?

 

What is the impact of changing the "Rate" entry in the P3 Menu?

 

73,

K1ESE

John

 

 

 

 


Re: P3 Questions

Al N1AL
 

The waterfall is updated at the rate of the spectrum display update.  So if you slow down the display update using the "Rate" command it will slow down the waterfall speed as well.

Alan N1AL


On 11/21/2020 8:47 AM, John Huffman wrote:
I have a 'new to me' P3 (no P3SVGA) and have a couple of questions.

Is it possible to slow the speed of the waterfall?

What is the impact of changing the "Rate" entry in the P3 Menu?

73,
K1ESE
John





Re: [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

Richard Williams
 

I just checked my K3S (using a solid state switching supply), and in receive the voltage on the meter shows 14.3 V (1.4 A), at 70W, 13.9V 18A), and at 100W 13.7V (21A)

Not sure if that is a big issue or not?  I did not measure the voltage or current draw at the PS, but on the meter in the K3S.

Dick, K8ZTT

Flying is the second greatest thrill known to man.
What is first, you ask? Landing, of course.
"A good aviator will always have his take-offs plus landings divisible by 2!"







On Saturday, November 21, 2020, 09:49:14 AM MST, Ray Maxfield <wa6vab@...> wrote:


Chet.

I am not aware of any Internal components that Age.

But You bring up a Good point, on the power Supply…..

Try doing a Load Test at a Higher Current.

And…. If you can Swap out the power Supply even better.

Also…. Any Crimp Lugs in the System….. 

Ray   VAB

 

From: Chet, N8RA
Sent: Saturday, November 21, 2020 6:48 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

 

Thanks Ray.

The disp shows 14.4 V in rx and 14.0 at 70W out.

Are there any internal power supply components that may have aged over the years e.g. electrolytic capacitors that have bulged or dried out?

Hmm.. maybe I should look inside my Astron supply too.

73,

Chet, N8RA

 

 

From: Elecraft-K3@groups.io <Elecraft-K3@groups.io> On Behalf Of Ray Maxfield
Sent: Friday, November 20, 2020 1:43 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

 

Chet……..I would Check ALL the +12 Volts Connections.

The Anderson Pole Connectors have been a Issue in the Past,

Make sure you have the Genuine ones.    Ray WA6VAB

 

 

From: Chet, N8RA
Sent: Friday, November 20, 2020 8:25 AM
To: elecraft@...; Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

 

Alas, my K3 power out problem WAS NOT SOLVED by replacing the LPA MOSFETs.

 

Upon first turn on, the xmit power could be set high on all bands as expected.

 

But then, after  a few hours of the radio just sitting there in receive, going to transmit it would not reach a power output past ~40 watts (varied by band and varies a few watts as it sits in transmit) and will fail the transmit gain calibration.

 

Picking up on a possible related thread, I took off the bottom rear case panel and tested the two SWR bridge diodes. They both appear to be good according to my DVM Is that a good enough test?

 

My 12V supply voltage was a bit low according to other owners (13.4 v dropping to 12.9 v on XMIT)) so I adjusted the Astron SS-30M to 14.5 volts. Now, setting the xmit power higher works when going to TUNE, and the radio passes all the calibrate xmtr gain tests. So again I thought maybe that was it.

 

But again, nope. After being on for over 8 hours in receive, and heating up internally, it fails to reach the set 70W output.  But after being turned off for about 2 hours, it resumed producing the set 70W. See the attached chart.

 

 

Something temperature, voltage, time  related?

 

Any other ideas out there?

 

Chet, N8RA

 

 

-----Original Message-----
From: Chet S <chetsubaccount@...>
Sent: Tuesday, November 17, 2020 9:22 AM
To: 'elecraft@...' <elecraft@...>; 'Elecraft-K3@groups.io' <Elecraft-K3@groups.io>
Subject: RE: [Elecraft] my K3 has some issues-SOLVED- Low Power Amp MOSFETs

 

Replacing the final output MOSFETs in my K3’s  low power amp appears to have fixed its transmit power issues. Thank you everyone on the K3 forums for your shared advice and experiences.

 

The “3 screw” tests were pointing to a bad output transistor in the LPA. The idle current increase on the K3 meter when putting the radio into XMIT (not TUNE) was only 310 ma, where at least 600ma was expected, again pointing to a FET being open.

 

To be sure of getting the right vintage of FETs, I ordered a couple of them (and thermal insulator) from Elecraft. My order was shipped that same day and arrived via priority mail 2 days later. Great service.

 

Following the procedure described by others, I replaced both output MOSFETs. Since one had been inoperative, the other had been carrying the whole load to produce output so may have been overworked, overstressed and hurting.

 

Here are my additional comments on the repair process:

 

1) The Elecraft document “KPA3CONMDKT MOD Kit Manual” has a wonderful description of how to remove and replace the 100W amplifier to allow access to the LPA’s adjustment potentiometers.

 

2) Turning the power to zero is a good safeguard when doing the bias adjustment I also made sure the radio was in USB or LSB so no power output would be commanded in any case.

 

Now with the FETs replaced and the bottom cover back on, the moment of truth….

 

Three LPA potentiometers turned down.

Turn first pot, +200ma.

Turn second pot, another 200ma.

Turn third pot, yet another 200ma.

Success!

 

Put the 100W amp module back in and connected to the Elecraft K3 utility.

All 3 transmitter gain tests passed, and now the power setting is stable on all bands.

 

On 40M where the reported SWR into a dummy load before the repair was 1.4 instead of 1.0  was now down to 1.2. Still do not know why but I can certainly live with that.

 

So… why did this even happen in the first place?

I can only speculate.

Older generation MOSFETs were difficult to keep in their safe operating region without snubbers. Did some transient zap it?

Power semiconductor chip bonding is subject to failure after a high number of thermal cycles, and this has been a contest radio.

In January during the VHF contest, my 6M antennas became badly detuned with wet snow and ice accumulation. This led to a high swr propagating thru the transmit chain to the K3 which suffered a total loss of power output on 6M with a very high swr indicated. After a rest, the K3 recovered, but did that event set this failure in motion? GOK.

 

And a closing suggestion- if your K3 is working OK now, save a copy of its configuration: this may turn out to be quite handy in the future.

 

TU all and 73,

Chet, N8RA

 

 

 

-----Original Message-----

From: elecraft-bounces@... <elecraft-bounces@...> On Behalf Of Chet S

Sent: Tuesday, November 10, 2020 4:02 PM

To: elecraft@...

Subject: [Elecraft] my K3 has some issues

 

Good afternoon K3 folks,

 

I am new to this list and honored to be accepted.

 

Recently my K3 has experienced a couple of issues. I have been unable to get a response from Elecraft e-mail or telephone service regarding the situation. It's been almost two weeks now so thought I'd ask here if anyone has some suggestions for me to try myself.

 

Here is the main concern:

 

When getting ready for CQWWDX SSB a few weeks ago, I went through setting the transmit power on each band to drive an amplifier properly. The power display seemed a bit sluggish and had a delay in indicating the SWR. Worse yet, when I got to 40M, I could not crank the power up past about 30 watts; it would momentarily display a higher number but then fall back to 30w. All other bands cold be set higher.

 

First I reloaded all the current firmware in the main and subreceiver. No change to 40M.

 

So next I went to the K3 Utility ver 1.20.1.15 to do a transmitter gain calibration. Starting with the 5W calibration, it stepped thru the first few bands OK but then stopped (I think on 40M) and displayed "ERR TXG" and the message "calibration settled at 3.6W, TX gain failed because transmit power did not reach the expected value".

 

In anticipation of having to send the radio to Elecraft where it might be totally reset, I manually started recording all the configuration settings.

When I looked at my filter settings, I was shocked to see that filter 1 in the subreceiver was set to 1.35. Huh? It should have been 2.80 !! Was my config info corrupted? I reset that to 2.80 and then for the heck of it tried again to set the power on 40M. That now  worked "OK"  and the swr and pwr display during "tune" showed instantly on all bands. Something had changed.

 

Next, I decided to rerun the TX calibration gain routine. This time if successfully completed the 5w and 50w routines. However, with a good dummy load, 40M displays an swr of 1.4, while the other bands are 1.0 or 1.1, so something is still a little funny on 40M. What might that be?

 

I have now been considering doing a total reset of the radio using the EE INIT function and then the self calibrations. Is this wise?

 

Any experiences or suggestions appreciated.

 

73,

Chet, N8RA

 

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Re: [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

Ray Maxfield
 

Chet.

I am not aware of any Internal components that Age.

But You bring up a Good point, on the power Supply…..

Try doing a Load Test at a Higher Current.

And…. If you can Swap out the power Supply even better.

Also…. Any Crimp Lugs in the System….. 

Ray   VAB

 

From: Chet, N8RA
Sent: Saturday, November 21, 2020 6:48 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

 

Thanks Ray.

The disp shows 14.4 V in rx and 14.0 at 70W out.

Are there any internal power supply components that may have aged over the years e.g. electrolytic capacitors that have bulged or dried out?

Hmm.. maybe I should look inside my Astron supply too.

73,

Chet, N8RA

 

 

From: Elecraft-K3@groups.io <Elecraft-K3@groups.io> On Behalf Of Ray Maxfield
Sent: Friday, November 20, 2020 1:43 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

 

Chet……..I would Check ALL the +12 Volts Connections.

The Anderson Pole Connectors have been a Issue in the Past,

Make sure you have the Genuine ones.    Ray WA6VAB

 

 

From: Chet, N8RA
Sent: Friday, November 20, 2020 8:25 AM
To: elecraft@...; Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] [Elecraft] my K3 has some issues-NOT SOLVED- LowPower Amp MOSFETs

 

Alas, my K3 power out problem WAS NOT SOLVED by replacing the LPA MOSFETs.

 

Upon first turn on, the xmit power could be set high on all bands as expected.

 

But then, after  a few hours of the radio just sitting there in receive, going to transmit it would not reach a power output past ~40 watts (varied by band and varies a few watts as it sits in transmit) and will fail the transmit gain calibration.

 

Picking up on a possible related thread, I took off the bottom rear case panel and tested the two SWR bridge diodes. They both appear to be good according to my DVM Is that a good enough test?

 

My 12V supply voltage was a bit low according to other owners (13.4 v dropping to 12.9 v on XMIT)) so I adjusted the Astron SS-30M to 14.5 volts. Now, setting the xmit power higher works when going to TUNE, and the radio passes all the calibrate xmtr gain tests. So again I thought maybe that was it.

 

But again, nope. After being on for over 8 hours in receive, and heating up internally, it fails to reach the set 70W output.  But after being turned off for about 2 hours, it resumed producing the set 70W. See the attached chart.

 

 

Something temperature, voltage, time  related?

 

Any other ideas out there?

 

Chet, N8RA

 

 

-----Original Message-----
From: Chet S <chetsubaccount@...>
Sent: Tuesday, November 17, 2020 9:22 AM
To: 'elecraft@...' <elecraft@...>; 'Elecraft-K3@groups.io' <Elecraft-K3@groups.io>
Subject: RE: [Elecraft] my K3 has some issues-SOLVED- Low Power Amp MOSFETs

 

Replacing the final output MOSFETs in my K3’s  low power amp appears to have fixed its transmit power issues. Thank you everyone on the K3 forums for your shared advice and experiences.

 

The “3 screw” tests were pointing to a bad output transistor in the LPA. The idle current increase on the K3 meter when putting the radio into XMIT (not TUNE) was only 310 ma, where at least 600ma was expected, again pointing to a FET being open.

 

To be sure of getting the right vintage of FETs, I ordered a couple of them (and thermal insulator) from Elecraft. My order was shipped that same day and arrived via priority mail 2 days later. Great service.

 

Following the procedure described by others, I replaced both output MOSFETs. Since one had been inoperative, the other had been carrying the whole load to produce output so may have been overworked, overstressed and hurting.

 

Here are my additional comments on the repair process:

 

1) The Elecraft document “KPA3CONMDKT MOD Kit Manual” has a wonderful description of how to remove and replace the 100W amplifier to allow access to the LPA’s adjustment potentiometers.

 

2) Turning the power to zero is a good safeguard when doing the bias adjustment I also made sure the radio was in USB or LSB so no power output would be commanded in any case.

 

Now with the FETs replaced and the bottom cover back on, the moment of truth….

 

Three LPA potentiometers turned down.

Turn first pot, +200ma.

Turn second pot, another 200ma.

Turn third pot, yet another 200ma.

Success!

 

Put the 100W amp module back in and connected to the Elecraft K3 utility.

All 3 transmitter gain tests passed, and now the power setting is stable on all bands.

 

On 40M where the reported SWR into a dummy load before the repair was 1.4 instead of 1.0  was now down to 1.2. Still do not know why but I can certainly live with that.

 

So… why did this even happen in the first place?

I can only speculate.

Older generation MOSFETs were difficult to keep in their safe operating region without snubbers. Did some transient zap it?

Power semiconductor chip bonding is subject to failure after a high number of thermal cycles, and this has been a contest radio.

In January during the VHF contest, my 6M antennas became badly detuned with wet snow and ice accumulation. This led to a high swr propagating thru the transmit chain to the K3 which suffered a total loss of power output on 6M with a very high swr indicated. After a rest, the K3 recovered, but did that event set this failure in motion? GOK.

 

And a closing suggestion- if your K3 is working OK now, save a copy of its configuration: this may turn out to be quite handy in the future.

 

TU all and 73,

Chet, N8RA

 

 

 

-----Original Message-----

From: elecraft-bounces@... <elecraft-bounces@...> On Behalf Of Chet S

Sent: Tuesday, November 10, 2020 4:02 PM

To: elecraft@...

Subject: [Elecraft] my K3 has some issues

 

Good afternoon K3 folks,

 

I am new to this list and honored to be accepted.

 

Recently my K3 has experienced a couple of issues. I have been unable to get a response from Elecraft e-mail or telephone service regarding the situation. It's been almost two weeks now so thought I'd ask here if anyone has some suggestions for me to try myself.

 

Here is the main concern:

 

When getting ready for CQWWDX SSB a few weeks ago, I went through setting the transmit power on each band to drive an amplifier properly. The power display seemed a bit sluggish and had a delay in indicating the SWR. Worse yet, when I got to 40M, I could not crank the power up past about 30 watts; it would momentarily display a higher number but then fall back to 30w. All other bands cold be set higher.

 

First I reloaded all the current firmware in the main and subreceiver. No change to 40M.

 

So next I went to the K3 Utility ver 1.20.1.15 to do a transmitter gain calibration. Starting with the 5W calibration, it stepped thru the first few bands OK but then stopped (I think on 40M) and displayed "ERR TXG" and the message "calibration settled at 3.6W, TX gain failed because transmit power did not reach the expected value".

 

In anticipation of having to send the radio to Elecraft where it might be totally reset, I manually started recording all the configuration settings.

When I looked at my filter settings, I was shocked to see that filter 1 in the subreceiver was set to 1.35. Huh? It should have been 2.80 !! Was my config info corrupted? I reset that to 2.80 and then for the heck of it tried again to set the power on 40M. That now  worked "OK"  and the swr and pwr display during "tune" showed instantly on all bands. Something had changed.

 

Next, I decided to rerun the TX calibration gain routine. This time if successfully completed the 5w and 50w routines. However, with a good dummy load, 40M displays an swr of 1.4, while the other bands are 1.0 or 1.1, so something is still a little funny on 40M. What might that be?

 

I have now been considering doing a total reset of the radio using the EE INIT function and then the self calibrations. Is this wise?

 

Any experiences or suggestions appreciated.

 

73,

Chet, N8RA

 

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