-------- Original Message -------- Subject: Re: [Elecraft] K2/100 pwr out control problem Date: Fri, 22 Apr 2011 21:22:17 +0000 From: Robert G. Strickland <[email protected]> To: [email protected]
Don... The base K2's power is continuously adjustable from low to over 10w as measured by the RF probe. However, the Vrms readings don't jibe w/ the power out as indicated on the K2 lcd. I did run the bare K2 through my antenna tuner that has a cross needle forward/reflected meter [yes, they're barely accurate at best] and that showed continuously variable power from nil to quite a bit over 10w indicated. The exact power reading at this point is indeterminate, but I'm pretty sure that it's up there. When this problem started, I noticed it by not being able to control the power out from the amp; it was being driven to around 700w out [too much]. To do this would require a drive level of around 50w from the K100 which would, in turn, require "something" from the base K2. I'll get some diodes and report back. Thanks. ...robert On 4/22/2011 20:55, Don Wilhelm wrote: > Robert, > > Yes, that is the first step. > > The K2s attempt to drive the power higher (the microprocessor thinks the > power output is low) may have damaged one of the base K2 PA transistors, > but replace the diodes first and then that check can be made. > > If you have to order the diodes from Elecraft, you may want to check on > the health of the base PA first. > To do that, remove the KPA100 and check the maximum power output > available from the base K2. If you cannot get at least 10 watts out of > it on most bands (all exxcept for possibly 10 meters), then it is likely > the PA transistors must be replaced - order K2PAKIT from Elecraft. > > 73, > Don W3FPR > > On 4/22/2011 4:33 PM, Robert G. Strickland wrote: >> Hello, Don and others.. >> >> Thanks for everyone's suggestions. Much appeciated. The problem >> persists regardless of using an antenna or a dummy load. I carried out >> Don's suggestions as described below. >> >> I don't have a watt meter, so I used the RF probe on a 50ohm resistive >> load and calculated the Vrms for the various power levels. Calculated >> and observed readings are as follows: >> >> Power Vrms [cal] Vrms [observed] >> 10w 22.36v 18.0v >> 5w 15.8v 18.0v >> 2w 10.0v 18.0v >> >> Computed power out at 18.0Vrms is 6.48w >> >> In addition, I notice the following LCD readings at all three power >> levels: the moment the TUNE button is pressed a HI CUR reading appears >> that immediately changes to a power out reading is 2.1w and an SWR >> reading 9.9:1. Again these reading occur at all three power settings. >> >> Don, I'm going to assume that your first suggestion to change D16 and >> D17 still holds. Yes? >> >> ...robert >> >> On 4/22/2011 15:47, Don Wilhelm wrote: >>> Robert, >>> >>> Make the following setup and check into a dummy load with an external >>> wattmeter between the K2 and the dummy load. Please follow the testing >>> method given, there is a reason for that test methodology. >>> 1) Remove the APP power cord from the KPA100 and power the K2 only from >>> the coaxial power jack on the lower rear panel. Set the K2 to 40 meters. >>> 2) Set the power requested knob to 5 watts and press TUNE - what is the >>> power on the external meter? >>> 3) Set the power to 2 watts and again press TUNE - what is the power on >>> the external meter? >>> >>> If the actual power was 10 watts or more in both cases above, change >>> diodes D16 and D17 in the KPA100. >>> If the actual power tracked the requested power, then you have a >>> different problem - power the KPA100 from the APP power cable and try >>> again into a dummy load (not an antenna). Set the power requested to 50 >>> watts and do a TUNE - the actual power should be near 20 watts. If it >>> goes to a large value, then we need to investigate your KPA100 - remove >>> it from the base K2 and take the shield off, and let us know the status >>> of your results. >>> >>> 73, >>> Don W3FPR >>> >>> On 4/22/2011 10:46 AM, Robert G. Strickland wrote: >>>> I'm running a K2/100 Ser# 5957, operational for about three years. Just >>>> now, control of pwr out has become intermittant. I can control pwr out >>>> in the basic K2 thru the range 0 -13w. Anything over that and the K2 >>>> meter sticks at about 13w, but the amp output jumps immediately and >>>> somewhat randomly to between 50-100w with no "smooth" control. >>>> Decreasing the K2 pwr out below 10w or so, and the overall pwr out >>>> drops >>>> accordingly, the K2 meter reads "correctly," and the total unit pwr out >>>> (external meter) agrees with the K2 meter. I've tried cycling on/off, >>>> different bands, different modes. All the same. Any suggestions most >>>> welcome. >>>> >>>> ...robert >>>> >>> >> > -- Robert G. Strickland, PhD, ABPH - KE2WY [email protected] Syracuse, New York, USA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
