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

[Nr4c]

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 <pincon at erols.com> 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: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On
> Behalf Of Mike K8CN
> Sent: Sunday, March 10, 2019 8:25 PM
> To: elecraft at mailman.qth.net
> 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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