+++++++++++++++++++++ Date: Tue, 16 Jul 2002 23:11:23 -0500 From: Mike To: elecraft at mailman.qth.net Subject: [Elecraft] Re-work of K1 #175 I just finished a job on my K1 that I was not much looking forward to, using parts recently received from Elecraft. (1) Pulled the front panel and replaced the AF gain pot, which had become scratchy several months ago. I haven't heard anyone else report K1 scratchy pots, so maybe just mine had a problem. The new pot seems to have significantly less shaft woble than the original pot. I may have to order another one and replace the RIT pot. (2) BIG JOB! Pulled off all 16 of the old problematic ceremic trimmers on the KFL1-4 PCB and replaced them with the "new" blue trimmers. I found it was easy to get the old trimmers off, since there was plenty of room under the old trimmers to get something to pry one end up while desoldering. I didn't even damage them. Getting the residual solder out of the vacated hole, and forming the thicker leads of the new caps to get them on the PCB was another story altogether. I was never able to get the holes so clean that the new caps would slip right in, so I wound up just blowing most of the solder out, then heating the holes alternately while I pressed the new cap down. I did have one problem that I didn't find until I was in the alignment phase. Trimmer C1 adjustment had no effect. I found quickly that the ground connection PCB trace to C1, which was on the top of the PCB and therefore buried under C1, was broken. A short jumper installed below the PCB to the ground side of C5 corrected that. Though I can't honestly say that I enjoyed this task, all in all it wasn't as bad as I had feared. (3) Changed C10 and CK in the 30m/40m portion of the pass band circuits of the KFL1-4 from 3 uuf to 4.7 uuf. Though this was recommended in the KFL1-4 temperature stability bulletin as an alternative to replacing the trimmer caps, that's not why I made this change. I have a 170 kHz VFO span option, but with the KFL1-4 I've never been able to align 40m such that I could get the same power output on both ends of the band. In fact, if I aligned the KFL1-4 for 7 watts out at 7070 kHz, I was lucky to be able to get 2 watts out at 7150 kHz, and 5 watts at 7000 kHz. Changing these two caps now allow my K1 to produce very near maximum power all through the 170 kHz tuning range on 40m. (4) Installed the new RFC9 in the attenuator relay circuit to eliminte pop on switching. (5) Installed the new RFC8 in the 12v supply to the low level transmitter stages, as recommended by Elecraft if an 80m board is to be used. I haven't started on rebuilding an old two band KFL1 for 80m/17m yet, but I have parts now for those bands. I can't think of any reason not to have RFC8 in the circuit, even though the new K1 kits have a jumper installed in its place unless an 80m board is to be used. Anyway, my old K1 is back and better than ever. Great rig! Mike / KK5F ++++++++++++++++++ Date: Wed, 17 Jul 2002 09:10:13 -0500 From: Mike To: Paul Cavnar Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] Another K1 Comes to Life Paul Cavnar wrote: > I am pleased to announce that K1 #1256 has been born... Congratulations! > Next comes the list of mods that I may do ... Likely, I > will do none. :) If yours is of the latest version (manual revision F), there's *very little* left in the way of significant mods. Just about all the issues and improvements developed since the K1 and the KFL1-4 were introduced have been incorporated in the later units. About the only electrical mods I can think of that aren't are just matters of tailoring a feature or two to one's own personal liking: (1) AGC response time decrease (RF board C31 changed to 1 uF or so). (2) KFL1-4 40m bandpass broadening (C10 and CK to 4.7 uuF) if you have a 150 kHz or greater VFO range and want near full output over that range). (3) RIT range reduction (I've not incorporated this one). (4) Backlighting the LCD (I've not incorporated this one). Beyond that are the minor non-electrical improvements, like: (1) Speaker grill cloth - more important than one might think, to keep crud out of the speaker cone and improve appearance. (2) Felt "washers" behind the tuning knob to create some resistance to rotation - strictly a personal choice, but I've found this to be valuable with my 170 kHz VFO tuning range. (3) At one time, a "resonace rattle" could occur at certain audio frequencies unless the four corners of the front panel PCB had some small amount of foam tape between them and the fastening blocks on the main chassis. I've heard no more about this for over a year, so I guess this has been resolved. (4) At some audio frequencies, a rattle could occur between the speaker magnet and the mounting bracket of the KBT1 internal battery unless a single layer of tape was wrapped around the speaker magnet. I haven't heard anyone mention this as a problem in a long time either. I'm sure there's other mods out there, but if I had a new K1 I personally would do all the above except the RIT mod (I like the RIT range as designed) and the LCD backlight (I don't want the extra current consumption). Every other mod I've done to K1 number 175 in the past 21 months has already been incorporated into the latest units. 73, Mike / KK5F ++++++++++++++++++++ From: "Wallace, Andy" To: elecraft at mailman.qth.net Subject: RE: [Elecraft] Another K1 Comes to Life Date: Thu, 18 Jul 2002 13:49:10 -0400 > -----Original Message----- > From: Mike [mailto:mmorrow at companet.net] > > I'm sure there's other mods out there, but if I had a new K1 I > personally would do all the above except the RIT mod (I like the RIT > range as designed) I modified my K1 with the RIT fine-coarse mod as described in the Archives at: http://www.qsl.net/ve3mcf/elecraft_reflect/K1_mod_RIT_Fine-coarse_Feature.tx t I had previously changed my RIT to have more range for working split, and so my fine-coarse mod used different resistor values. When I get a chance, I'll document and post the way I did it. This mod gives a fine-tuning semi-detent in the center of the pot's range. I think it works pretty well. > and the LCD backlight (I don't want the > extra current > consumption). Is 4 mA too much? I performed the mod as described in: http://www.qsl.net/ve3mcf/elecraft_reflect/K1_Lighted_Display.txt and used a pair of Radio Shack bright-white ($5 each) LEDs. Actual color is sort of bluish. Not unattractive. Limiting resistor is a 1.2K surface mount part mounted by the connector (picking off 12VDC from the front panel). Works as well as it can. Part of the problem is that the K1 LCD is close to the front panel. To illuminate it with regular LEDs from the side, it would help if the display was mounted lower to the board. If I ever build another K1, I might try shortening the LCD spacer to allow this. Sure would be nice if lighting could be a standard thing -- maybe some of those small surface mount LCD illuminator strips? I checked the manufacturer's website and they don't offer the model used in the K1 with an integral backlight. -Andy ++++++++++++++++++++