VFO runs away / Arc Fault on Acom 2000A

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  • Problem
  • Updated 4 years ago
  • (Edited)

Flex 6500  V1.6.17

The VFO runs away, all the time. I have to get lucky and stop it with the lock button.

And my Acom 2000A kicks out and says "Arc Fault" if I go above 500 or 600 watts. (SSB)  SWR / ALC....everything is as it should be. I switch over to my Kenwood TS-940S and run 1500 Watts all day long, no problem. Same antenna and all.  I paid way too much for this radio to have these problems. Aggravated......but still love my flex!



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Steve Parker

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Posted 4 years ago

  • 2
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KY6LA - Howard, Elmer

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Steve Parker

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So, 2 Knob radios (other being a Yaesu 1000D) runs flawless......1500 watts with no issue, and RFI in shack? .......I don't think so. Or the knob radios are just shielded better.
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KY6LA - Howard, Elmer

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I my experience SDR's have many more points for RFI ingress and Egress such as the computer and network conneCtions not found in Legacy Radios. Very easy to have a ground loop between computer, network and radio.
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K6OZY, Elmer

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Do you have the flex knob? Could be RFI into that USB cable too.
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When I received my 6500, I had the same problem with frequency scanning. Had to lock it to keep it at one frequency.  It turned out to be a bad connection in the microphone.  To test this, unplug the microphone and see if the frequency scanning stops.
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Steve Parker

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Well..... just checked 40M & 160M antennas (inverted V dipoles), 1500 watts no problem. Hmmmmm ..... Balun  maybe, connection?......things to check I guess.    
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Gary m0gme

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Had similar problem with acom1000 . Had been running flex straight from PC. Ferrite on cat cable helped, but running flex to the router solved everything. Gary m0gme
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WW1SS - Steve

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I too have a problem with the VFO. The slice gets near the edge of the display while tuning and it just goes on and on and on. Only way for me to stop it is shut down SDR.
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Ken - NM9P

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@Steven, your problem may be caused by the FIFO buffer on the com port you are using for the FlexControl Knob. Go to device manager and find the com port. Then go into properties>advanced and turn the FIFO buffer OFF, and slide the buffer sliders all the way down. See if that helps.

Ken - NM9P
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My sentiments exactly. It's been bitter sweet. We will have to see if the sweet is enough to sustain my interest.
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Frank WA3NHK

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As a second check on the flex knob RFI theory (if you have the knob), push the button to make it control your audio volume rather than VFO.  If the volume runs away then this is probably at least part of your problem.  But your HPA fault may indicate you have more than one failure mechanism at issue.
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Eric - KE5DTO, Official Rep

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We have seen at least one instance in the office where the front panel microphone was wired in such a way that the tune up/down buttons were shorted.  Thus, as soon as you started the radio up, it would start trucking up the band.  Try disconnecting the front panel microphone if you have one connected and are seeing behavior like this.

If that is not what is going on, please describe what is going on right before this starts.  How are you tuning the Slice?  FlexControl?  Mousewheel?  Drag 'n' drop with the mouse?  This may help us home in on what is causing the issue.  If the issue is reproducible across multiple units, it is likely a bug.  Then the goal is to find a reliable way to reproduce the issue so we can turn it over to our development team to squash it.

Please keep us posted.  We're here to help.
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Anthony Bowyer

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One area that should be carefully addressed is rfi getting into the ANY USB port. This will cause odd issues. It can be very freq selective and power level dependent.

I found, on one device in particular, I had to get 6 foot USB cable extensions and put two large clip- on common mode chokes on them (with as many turns of the cable wrapped around them as possible). Plus two on the cable itself (the one on the device, and this device had no relation to any xcvrs, etc). Three dif PC's, 2 from commercial sources and one I built myself, all had this problem to one degree or another. An HP desktop was by far the worst of the bunch. Seems the MB USB hub mistook RFI as a power surge would shut it down).

And this was in a very clean RFI environment. I suspect RFI protection on said ports is sorely lacking.

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Steve Parker

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I'm going through rear for mic, and I do have the Flex knob, but haven't been using it. I'm using mouse. I will try the suggestions. Thx
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If the issues were just with your Flex I'd agree it was perhaps due to RF in the shack, but your Arc Fault issue with your A2000A makes me think there might be an over drive issue, at least during the initial key up.  ALC range on the Flex is 0 to -4v and 0 to -11v (adj) on the Acom 2000A.  You might want to disconnect the ALC line completely and use DDUTIL to bring the drive level up slowly to see you experience the same issues.