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[K3] Spontaneous HI CURR, audio reduction in RX mode

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Mike K8CN

[K3] Spontaneous HI CURR, audio reduction in RX mode

Over the past several weeks, and especially during the NA Sprint CW contest
last Saturday night, I've noticed spontaneous brief flashing of the HI CURR
warning *in receive mode*, which is accompanied by an immediate reduction in
headphone audio (though not complete loss of audio). It is as though the
receiver's RF attenuator was switched in after the HI CURR warning was
flashed.

My K3/10 is up to date on all firmware and has a serial number in the 66XX
range if I recall properly. I have yet to discern any correlation with
transmit mode behavior, which has never displayed a HI CURR warning. My gut
instinct is that this may be one of those pin corrosion symptoms, especially
since I've had some strange responses to front panel button presses that are
not repeatable. The receive audio seems to come back, but I can't tell why
or when in relation to anything I've done with the radio controls........

Has anyone else seen the HI CURR warning displayed only in receive mode with
accompanying loss of receive signal strength? I've searched the archives
and found plenty of discussion about HI CURR warnings, but nothing quite
matches my K3's observed behavior in receive mode.

Mike, K8CN

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Mike K8CN

Re: [K3] Spontaneous HI CURR, audio reduction in RX mode

I believe I found a potential answer in the K3 manual (to my embarrassment, I
should have looked there first, eh?) under the Troubleshooting section,
Receive mode:

"HI CUR or SPKRS=1 warning: HI CUR may indicate a shorted left speaker
channel; the K3 will
reduce AF gain."

Funny thing is that I don't use the internal speaker, just headphones
connected via the rear panel PHONES jack, and have never plugged anything
into the external speaker jack.......I guess I'll unbutton the case and see
if any wiring is awry. The intermittency of the HI CUR warning in receive
mode is puzzling - if there's a shorted audio channel, I would think it
would stay shorted unless my headphones have an intermittent short on one
side.

Thanks, too, to Joe, 4Z7JBA, for his offline suggestion of another potential
cause for the observed behavior in receive mode.

Mike, K8CN

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Björn Ekelund

Re: [K3] Spontaneous HI CURR, audio reduction in RX mode

Mike,

do you have the latest firmware? I believe a similar issue was mentioned in
a firmware update.
I have experienced it myself at SK3W on a station with an outdated
firmware.

73,

Björn SM7IUN

Den tis 5 feb. 2019 kl 19:47 skrev Mike K8CN <[hidden email]>:

> I believe I found a potential answer in the K3 manual (to my
> embarrassment, I
> should have looked there first, eh?) under the Troubleshooting section,
> Receive mode:
>
> "HI CUR or SPKRS=1 warning: HI CUR may indicate a shorted left speaker
> channel; the K3 will
> reduce AF gain."
>
> Funny thing is that I don't use the internal speaker, just headphones
> connected via the rear panel PHONES jack, and have never plugged anything
> into the external speaker jack.......I guess I'll unbutton the case and see
> if any wiring is awry. The intermittency of the HI CUR warning in receive
> mode is puzzling - if there's a shorted audio channel, I would think it
> would stay shorted unless my headphones have an intermittent short on one
> side.
>
> Thanks, too, to Joe, 4Z7JBA, for his offline suggestion of another
> potential
> cause for the observed behavior in receive mode.
>
> Mike, K8CN
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
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>

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Mike K8CN

Re: [K3] Spontaneous HI CURR, audio reduction in RX mode

With thanks to Björn SM7IUN and Mike VP8NO for pointing me to the firmware
revision notes, I checked my installed firmware and the K3 Utility and find
them to be fully up to date. I'll go quiet on this issue until I've had a
chance to reload the firmware and open the case to explore the board
connectors. I appreciate the guidance from those with better memories of
firmware revision notes!

73,
Mike, K8CN

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Nr4c

Re: [K3] Spontaneous HI CURR, audio reduction in RX mode

In reply to this post by Mike K8CN

The phones jack does not have that restriction. Only the Speaker jack. They have different audio path.

Sent from my iPhone
...nr4c. bill

> On Feb 5, 2019, at 1:46 PM, Mike K8CN <[hidden email]> wrote:
>
> I believe I found a potential answer in the K3 manual (to my embarrassment, I
> should have looked there first, eh?) under the Troubleshooting section,
> Receive mode:
>
> "HI CUR or SPKRS=1 warning: HI CUR may indicate a shorted left speaker
> channel; the K3 will
> reduce AF gain."
>
> Funny thing is that I don't use the internal speaker, just headphones
> connected via the rear panel PHONES jack, and have never plugged anything
> into the external speaker jack.......I guess I'll unbutton the case and see
> if any wiring is awry. The intermittency of the HI CUR warning in receive
> mode is puzzling - if there's a shorted audio channel, I would think it
> would stay shorted unless my headphones have an intermittent short on one
> side.
>
> Thanks, too, to Joe, 4Z7JBA, for his offline suggestion of another potential
> cause for the observed behavior in receive mode.
>
> Mike, K8CN
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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KeithWE6R

Re: [K3] Spontaneous HI CURR, audio reduction in RX mode

Administrator

In reply to this post by Mike K8CN

Hi Mike;
Can you go to config menu item "FW REVS" an tell me what you see please?

If you are still getting the HI CUR warning, the U1 audio chip on the
DSP board may have partly failed and will be getting HOT!
It can heat enough to MELT the DSP board and cause an internal short
that destroys the whole board!
If you can catch it before that happens, you will save a lot of money
and grief.
If you take the top cover off, and the upper left area of the front
panel, directly behind the BAND up and down buttons, is the audio chip
on the DSP board.
It is a black cube about 1/2 square at the top corner of that board.
Stick a thermometer down there.
Keith WE6R
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Mike K8CN

Re: [K3] Spontaneous HI CURR, audio reduction in RX mode

Thanks, Keith, for the pointer on audio IC U1 on the DSP board. Visual
inspection shows no obvious sign of overheating on the IC or the DSP board
itself. Will have to find a thermometer with a fine tip probe to measure
surface temperature on U1 though - household thermometers I have are too
large to fit into that space.

73,
Mike, K8CN

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Ralph S

Re: [K3] Spontaneous HI CURR, audio reduction in RX mode

Harbor Freight Hand held IR laser thermometer is your best friend.
Hold trigger, aim visible light, read surface temperature.

Ralph ,W7HSG

> On February 6, 2019 at 8:59 PM Mike K8CN <[hidden email]> wrote:
>
>
> Thanks, Keith, for the pointer on audio IC U1 on the DSP board. Visual
> inspection shows no obvious sign of overheating on the IC or the DSP board
> itself. Will have to find a thermometer with a fine tip probe to measure
> surface temperature on U1 though - household thermometers I have are too
> large to fit into that space.
>
> 73,
> Mike, K8CN
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
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Mike K8CN

Re: [K3] Spontaneous HI CUR, audio reduction in RX mode - UPDATE

I may have found the cause of the anomalous HI CUR warning in **receive**
mode, thanks to my big orange Maine coon cat, Mr. Opie. In rubbing his chin
on the VFO B knob while I was listening last night, he rotated the control
to the 12V DC bus voltage display, which I then noticed was oscillating
between 13.6 V and 12.7 V. When I checked the DC bus current display, it
was oscillating between 0.4 A and 2.1 A - clearly something was amiss.

Tonight I checked the terminal voltage on my Astron RS20-A linear supply,
and found it to be stable at 13.7 V with no load (K3 turned off), but then
it dropped to 13.4 V with the K3 'on' in receive mode. I again checked the
K3's internal volt/ammeter readings and found the same periodic oscillation
in each one. Curious to know if the oscillation was due to an interaction
with the supply regulator, I swapped out the RS20-A for my Astron SS-30
SMPS, which I normally use with my K2/100 setup.

Lo and behold, the DC bus oscillations ceased!

I have not yet spent enough time listening using the alternate power supply
to know if the HI CUR warnings will also cease, but will do so over the
coming week. Fortunately, I don't have to watch the K3 display because the
HI CUR condition also reduces headphone audio substantially, which gets my
immediate attention.

Kudos to Mr. Opie for his uncanny sense of what might reveal a potential
cause of the spontaneous HI CUR warnings in receive mode.

73,
Mike, K8CN

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Charlie T, K3ICH

Re: [K3] Spontaneous HI CUR, audio reduction in RX mode - UPDATE

It would also be very helpful if you can find the cause of the problem
inside the RS-20A.
There's probably more of those particular supplies and their family than any
others.
I'm fairly sure they use the old reliable "723" regulator that has been
around since it seems, Hertz experimented with sparks.

As an old sage used to offer a useful piece of advice....."It's probably a
resistor or a capacitor or something".

73, Charlie k3ICH

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Mike K8CN
Sent: Sunday, March 10, 2019 8:25 PM
To: [hidden email]
Subject: Re: [Elecraft] [K3] Spontaneous HI CUR, audio reduction in RX mode
- UPDATE

I may have found the cause of the anomalous HI CUR warning in **receive**
mode, thanks to my big orange Maine coon cat, Mr. Opie. In rubbing his chin
on the VFO B knob while I was listening last night, he rotated the control
to the 12V DC bus voltage display, which I then noticed was oscillating
between 13.6 V and 12.7 V. When I checked the DC bus current display, it
was oscillating between 0.4 A and 2.1 A - clearly something was amiss.

Tonight I checked the terminal voltage on my Astron RS20-A linear supply,
and found it to be stable at 13.7 V with no load (K3 turned off), but then
it dropped to 13.4 V with the K3 'on' in receive mode. I again checked the
K3's internal volt/ammeter readings and found the same periodic oscillation
in each one. Curious to know if the oscillation was due to an interaction
with the supply regulator, I swapped out the RS20-A for my Astron SS-30
SMPS, which I normally use with my K2/100 setup.

Lo and behold, the DC bus oscillations ceased!

I have not yet spent enough time listening using the alternate power supply
to know if the HI CUR warnings will also cease, but will do so over the
coming week. Fortunately, I don't have to watch the K3 display because the
HI CUR condition also reduces headphone audio substantially, which gets my
immediate attention.

Kudos to Mr. Opie for his uncanny sense of what might reveal a potential
cause of the spontaneous HI CUR warnings in receive mode.

73,
Mike, K8CN

--
Sent from: http://elecraft.365791.n2.nabble.com/
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Nr4c

Re: [K3] Spontaneous HI CUR, audio reduction in RX mode - UPDATE

If the “723” doesn’t fix it, call Astron. They don’t have much of a customer service department, but the guy who answers the phone will sell you a replacement “control board” for $20.00 plus $7.00 shipping. Assuming the diodes and caps are still good.

Sent from my iPhone
...nr4c. bill

> On Mar 11, 2019, at 8:04 AM, Charlie T <[hidden email]> wrote:
>
> It would also be very helpful if you can find the cause of the problem
> inside the RS-20A.
> There's probably more of those particular supplies and their family than any
> others.
> I'm fairly sure they use the old reliable "723" regulator that has been
> around since it seems, Hertz experimented with sparks.
>
> As an old sage used to offer a useful piece of advice....."It's probably a
> resistor or a capacitor or something".
>
> 73, Charlie k3ICH
>
>
>
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On
> Behalf Of Mike K8CN
> Sent: Sunday, March 10, 2019 8:25 PM
> To: [hidden email]
> Subject: Re: [Elecraft] [K3] Spontaneous HI CUR, audio reduction in RX mode
> - UPDATE
>
> I may have found the cause of the anomalous HI CUR warning in **receive**
> mode, thanks to my big orange Maine coon cat, Mr. Opie. In rubbing his chin
> on the VFO B knob while I was listening last night, he rotated the control
> to the 12V DC bus voltage display, which I then noticed was oscillating
> between 13.6 V and 12.7 V. When I checked the DC bus current display, it
> was oscillating between 0.4 A and 2.1 A - clearly something was amiss.
>
> Tonight I checked the terminal voltage on my Astron RS20-A linear supply,
> and found it to be stable at 13.7 V with no load (K3 turned off), but then
> it dropped to 13.4 V with the K3 'on' in receive mode. I again checked the
> K3's internal volt/ammeter readings and found the same periodic oscillation
> in each one. Curious to know if the oscillation was due to an interaction
> with the supply regulator, I swapped out the RS20-A for my Astron SS-30
> SMPS, which I normally use with my K2/100 setup.
>
> Lo and behold, the DC bus oscillations ceased!
>
> I have not yet spent enough time listening using the alternate power supply
> to know if the HI CUR warnings will also cease, but will do so over the
> coming week. Fortunately, I don't have to watch the K3 display because the
> HI CUR condition also reduces headphone audio substantially, which gets my
> immediate attention.
>
> Kudos to Mr. Opie for his uncanny sense of what might reveal a potential
> cause of the spontaneous HI CUR warnings in receive mode.
>
> 73,
> Mike, K8CN
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
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>
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