Don, Thanks for the advice. I also got the advice from Joe, AA4NN, to move the P/S (an Astron RS-35M) away from the K2, as well as putting more distance between the K2 and TS440S. The KPA-100 was purchased this past winter. The schematic is dated 2/2004. The PCB seems to follow the schematic. I didn't see the two mods you mention, so I added them above board - tacking a 1K resistor across RFC3 and tacking a 68K resistor across R4 (resulting in about 40K). As the unit set there opened up with the K2 and amp separate, the mods seemed to help. After it all was closed up and completed, the 80M note is still a bit raspy. I moved the P/S as far away as the cables allowed (3 to 4 feet) and still have some roughness. I think the TS440S may be getting overloaded, so I will look for a different way to judge, probably on the air. Thanks for the help.
73, Phil NS7P -----Original Message----- From: Don Wilhelm [mailto:[EMAIL PROTECTED] Sent: Monday, October 09, 2006 2:02 PM To: Phil and Christina; elecraft@mailman.qth.net Subject: RE: [Elecraft] Another KPA-100 problem Phil, It sounds like you may have the 160/80 meter low frequency oscillation problem in your KPA100. What is the vintage of this KPA100? Specifically, does it have the 1K ohm resistor across RFC3? That change was intended to attack a problem with a low frequency oscillation on 160 and 80 meters. The other part of the same change was to decrease the value of R4 to 39k (from 100k) to raise the high voltage fed to the T/R switch. If your KPA100 does not have these changes, consider putting them on and then check 160 and 80 meters again. If this KPA100 is one of the first, then putting the KPA100 upgrade kit on it may help. If your KPA100 has the C82 position populated and a resistor at R23 rather than a jumper, it has not been upgraded. 73, Don W3FPR > -----Original Message----- > > I worked through the intermittent problem I had last week. Oddly > enough, it > was a defective 100k pot at R26. > > I have been going through the alignment procedures and everything is OK > until I am finishing up the transmit tests and check signal quality on all > the bands. All is OK, except on 80 meters. On 80M both the CW > note and SSB > signal is raspy in the monitor receiver (a TS440 sitting on the bench). > Power output and all else seems OK on 80M, but the sound is > rough. Looking > at the schematic, I note that 80M has its own LPF path, but I would think > the power output would be off if something is wrong there. > > Any suggestions of where to look? Thank you. > > 73, > > Phil Shepard > NS7P > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
