That would not cause the KAT500 to shut down, though. In the situation you describe the KPA500 would continue to output power unless the HV supply drops below 40V. What I am saying is that if the 117V power supply on the KPA500 sags, the amplifier will just keep going, using what it gets. The output will show a corresponding sag, but no failures should result.
The KPA should use the beefiest power cable you can find. Use of a small cable will also cause the power to sag, again with the output sagging, but that is all. A good feel of the power cable will show it to be somewhat warm, which means you are losing power through I squared losses in the cable. A heavier cable (like the one supplied) should not show this nearly as much. Again, I don’t believe this is the problem that W6UX is seeing in the KAT500, though. - Jack B, W6FB Elecraft Engineering > On Jan 28, 2015, at 11:50 AM, Craig Buck via Elecraft > <elecraft@mailman.qth.net> wrote: > > I suspect voltage sag off the 120v line. Lights flickering is a symptom. > The specs call for 1000VA in and that translates to about 8 amps at 120v. > The specified fuse is 12 amps so peaks may be higher. Add everything else > in and consider you may have a 15 amp line with a long way back to the > fusebox and it is possible your voltage is dropping. Measure the AC voltage > with the key down by plugging a voltmeter into the outlet. Also check the HV > in the Amp. > > From the manual: > > The KPA500 operates to full specifications when the HV under full load is > between 60V and 85V as shown on the LCD (Tap HV to display the voltage > under CW “key down” conditions at full power). The maximum voltage is set > using transformer taps as described on pg. 9. > The KPA500 will operate with reduced performance at voltages as low as 40V. > When the voltage is less than 60V the maximum output power may be less than > 500W and distortion products will increase. > > K4ia Buck > Fredericksburg, VA > > On 1/28/2015 2:15 PM, Jeff Hall wrote: >> My KAT500 is getting power-cycled in CW and RTTY modes at various drive >> levels from the K3 on different bands. I can run SSB full power with no >> problems at all, and receive superb audio reports (no hint of RF in my >> transmissions). I am thinking I have either an excessive voltage drop on >> the AC circuit or perhaps there is enough RF getting into the shack to trip >> up the KAT500 power when using the higher duty cycle modes. >> Everything is running on the same 120v house circuit. I experimented with >> moving both the amp and the KAT500 to a different circuit in the same room, >> but this did not solve the problem. Let me first describe the equipment, >> and then I'll list the frequencies and power thresholds that tripped the >> KAT500 into a power cycle: >> Antenna: Traffie Hex Beam. Very low SWR, typically 1.2 or less, sometimes >> 1.5 on 10 and 12 meters. The antenna is over a portion of the house, and >> about 20 feet away from the shack. The coax is grounded at the base of the >> antenna (two ground rods, through a lightning arrestor). >> KAT500: I have this in BYPASS mode. I don't really need the tuner for the >> hex beam, but I plan on using it with a future vertical for 40m. I am >> powering the KAT500 with its own AC power adapter. For good measure, I >> wrapped about 4 turns of the power cord through a ferrite bead at the >> transformer end of the cable. This is a 15V 1000mAh power adapter from >> Radio Shack. >> KPA500 is plugged into the same circuit on its own outlet at the wall. HV >> reads 78.5 at rest. The unit is sitting on top of the KAT500 with the >> foldout legs extended. >> K3 is powered with an Astron RS-35M, on the same house circuit. >> P3 is powered by the K3 VDC out >> On 15 meters CW, the KAT500 begins to experience power cycles driving 20-22 >> watts. The amp, when it crosses about 450 watts, the KAT500 power cycles. >> I ran 30 watts into it for about 620+ out with no problems on SSB, SWR >> never exceeded 1.2 on the KAT500's indicator lamps. >> On 12 meters CW, the KAT500 begins to experience power cycles driving just 9 >> watts (about 180w out). SWR on this band is a steady 1.5. I did have some >> success by moving the KAT500's power adapter to the other circuit in the >> room and was able to push the K3 to 22 watts (480 out) before the >> powercycling returned. This lead me to believe I had a voltage drop issue, >> perhaps from running the amp on the same 110 circuit. But on 10 meters I >> still had problems even using the other circuit to power the KAT500. That >> makes me think noise is getting into the KAT500, or perhaps RF from the >> antenna is putting noise on my AC house circuits. I was able to run the amp >> to full power on SSB with no power cycling of the KAT500. >> On 10 meters the KAT500 power cycles with just 6 watts drive (170 out). On >> phone I can run full power with no issues. SWR is 1.2 on this band. >> >> I have a Morgan AC line filter arriving tomorrow and I'll see if the problem >> persists with it filtering the house circuit feeding the shack equipment. >> >> Do these symptoms smell more like a noise issue (RF in the shack) or a line >> voltage deficiency with the house circuit? I'm think probably taxing the >> line in the higher duty cycles, and it just manifests at different >> thresholds on different frequencies. >> When transmitting a long string of CW or RTTY, if the KAT500 gets into >> repeated power cycles the KPA500 eventually throws a fault. >> Some other observations: If I turn on my desk lamps, at the higher outputs >> the lamps will modulate slightly with my voice. I think I'm sucking too >> much juice from the circuit, but this is just a guess on my part. Generally >> the only other piece of equipment in the house that seems to be affected by >> RF is our DirectTV receiver (the notorious touch-panel design). It is >> generally only affected on 10 meters, with a high duty cycle mode like RTTY. >> Can anyone provide me some more troubleshooting tips? >> Thanks!Jeff, W6UX >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to k...@aol.com > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to jackbrin...@me.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
