+++++++++++++++++++ From: "COLIN WHITMORE" To: "Elecraft" Date: Fri, 6 Sep 2002 10:38:53 -0600 Subject: [Elecraft] K1 dead band on 20M Ok, Ok, Ok, I know, DON'T HAVE A RADIO HOOKED UP WHEN AN ELECTRICAL STORM= IS NEARBY, but I was showing a guy my K1 and didn't realize that a scatt= ered thunderstorm had scattered right near my house. Anyway I got zapped = and incidentally so did the poor little K1. I disconnected everything and= waited until the storm had passed then fired up the K1 to give it a once= over. Everything checked out fine; full power on all bands, ATU, transmi= t, receive, etc. Perfect, WHEW! A couple of days latter I was going on the air for the Spartan Sprint. I = hooked everything up and low-n-behold the ATU gives a PLO error on 20M. I= checked the other bands (40, 30 & 15) and the ATU tunes, the transmitter= transmits, and the receiver receives, just not on 20. I pulled out the ATU, re-soldered R36, and jumpered pins 2 & 10 of J2. I = attempted to re-peak the caps for 20 and still nothing; no power out, no = receive in. I've checked all the relays, they're working fine. All of the= resistance checks for the KFL1 are good. U1 is OK as are its voltage val= ues. Still all bands but 20 work so I don't think it's the ATU. Could it = be the crystal? I'm getting ready to build an RF probe to start signal tracing, but I fig= ured I'd post this and ask if I may be missing something obvious. Any sug= gestions? I just got a K2 and decided not to start on it until the K1 is = back to health. ;-) 72, Colin N=D8YGY ++++++++++++++++ From: Mike To: COLIN WHITMORE Cc: Elecraft Subject: Re: [Elecraft] K1 dead band on 20M COLIN WHITMORE wrote: > I checked the other bands (40, 30 & 15) and the ATU tunes, the > transmitter transmits, and the receiver receives, just not on 20. > > ... Could it be the crystal? There's a good chance. You can check. If you have an HF receiver, just drape an antenna lead to that receiver near the K1 PCBs. You should be able to hear the crystal oscillating around 22 MHz (mine oscillates at 21.9974 MHz) when you've got the 20m band selected. Mike / KK5F +++++++++++++++++++ From: "Scott Martin" To: "COLIN WHITMORE" , "Elecraft" Subject: RE: [Elecraft] K1 dead band on 20M Date: Fri, 6 Sep 2002 13:00:56 -0400 I had these exact symptoms and it was a bad xtal. I happened to have ordered a backup KFL board with 20M and used that xtal to verify my suspicions. Once replaced, all was well. 73, Scott AG4KU ++++++++++++++++++++ From: "COLIN WHITMORE" To: "Elecraft" Date: Fri, 6 Sep 2002 22:08:13 -0600 Subject: [Elecraft] K1 dead band on 20M - Follow-up Well I do believe that I've traced the problem down to the trimmer cap (C= C) on 20M. Tom's advice (copied below) was just the ticket. Placing the "= Cheap 'n Dirty Signal Tracer" on P2 pin 1 then P2 pin 8 (on KFL1) produce= d signals on all bands save 20M. This eliminated T3 and T4 as well as the= relays (verified with resistance checks) and the trimmer caps associated= with its respective band. Due to the lack of a signal on P2 pin 8 tells = me that the culprit has to be either CC or CD. A little history on trimmer CC; when I first completed the K1 I had probl= ems with 20M and it turned out to be the trimmer cap CC. The trimmer caps= have a little metal screwhead on the top and are soldered to a phenolic = wafer. When I attempted to peak the band I noticed that the screw would t= urn but not the wafer. After dropping a bit of solder to secure the screw= to the wafer, peaking the cap was no problem. I know I could have just a= sked Elecraft to send out a new cap but it was easier just to warm-up the= iron. Well I guess that little electrical shock was enough to make it finally g= ive up the ghost, so I guess in the end, I will be asking Elecraft to sen= d out a new cap. Though I believe for ten bucks I can get a set of their = less sensitive trimmer caps, maybe that's the route I'll go. Thanks to all who responded. And a special thanks to Tom (N=D8SS), his C&= D Signal Tracer really did the trick. 72 ES GD, N=D8YGY Colin K1 - #942 (weathering the storm, pun intended) K2 - #2833 (waiting patiently to be assembled) PS - I believe that the "Cheap 'n Dirty Signal Tracer" pdf file that Tom = sent me is available on Elecraft's website. =20 ----- Original Message ----- From: Tom HammondN=D8SS Sent: Friday, September 06, 2002 12:07 PM To: COLIN WHITMORE Subject: Re: [Elecraft] K1 dead band on 20M =20 Before you build that RF probe, which may be of limited utility, see if y= ou =20 can use my Cheap 'n Dirty Signal Tracing file to find your problem. Of course, tailor the BPF and LPF test points to the specific band on whi= ch =20 you are having a problem... in this instance, 20M. KK5F's suggestion to check the 20M Osc Xtal is a good idea as well... =20 probably worth checking BEFORE venturing into signal tracing. Good luck, hope this helps. Tom Hammond N0SS ++++++++++++++++++ Date: Sat, 07 Sep 2002 21:48:17 -0500 From: Mike To: COLIN WHITMORE Cc: Elecraft Subject: Re: [Elecraft] K1 dead band on 20M - Follow-up COLIN WHITMORE wrote: > ... I guess in the end, I will be asking Elecraft to send out a > new cap. Though I believe for ten bucks I can get a set of their > less sensitive trimmer caps, maybe that's the route I'll go. Replacing the white ceremic trimmers on the early KFL1-4 boards with the blue temperature stable trimmer caps is highly recommended. I put off doing it for months, but on occassion I found my K1 transmitter power very low on certain bands until I re-aligned the board. Since installling the blue caps, I've had no similar problems. I wish now that I'd done the replacements months earlier. I found that the 16 white ceremic trimmer caps were easy to unsolder without the aid of a solder sucker, since there was enough room under each to use a small screwdriver blade to pry the cap out. The only difficult part was getting the now empty solder holes sufficiently clean to allow the new caps to be mounted flush to the PCB. Even using a solder sucker and several passes, I was not able to get the holes clean enough for the replacement caps to just slide in. But a little heating while pushing gently on the caps worked just as well and just as quickly. While I had the KFL1-4 out, I doubled the size of C10 and CK to allow 7 watts out all across the 40m band from 7 to 7.16 MHz. Mike / KK5F +++++++++++++++