++++++++++++++++++ Continuation of KPA100 Build Notes See also KPA100 Debugging... I sometimes can't decide which is more appropriate...DWN ++++++++++++++++++ Date: Wed, 6 Nov 2002 00:06:37 -0500 (EST) From: kc4kgu at ENTERZONE.NET To: K9OZ at aol.com Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] How hot is too hot On Tue, 5 Nov 2002 K9OZ at aol.com wrote: > I got the KPA100 running with only minor troubleshooting, and it seems to be > running like a champ. Gave it a good workout in SS last weekend. But can't > find anything on how hot is too hot on the heat sink. > > If I wait for fan to come on (whether set on normal or low/high) it seems > like the sink gets pretty warm to the touch before the fan kicks in. The fan > seems to cool it, hold down heat well. So for the contest I just switched it > to High fan and let it run. > > But tonight in a casual QSO, top was hot again before fan kicked in. Is this > normal, or should I be checking things twice? > > Bruce, K9OZ, Bruce, When I did the KAT100 field test, the CAL tPA is one of the settings that I neglected to note. Since my thermostat is on the main floor of the house and my shack is in the basement, I didn't have any true reference to what the temp in the shack really was. To err on the SAFE side, here's what I did: I operated the rig into a dummy load until the top cover felt "warm to the touch" and then adjusted CAL tPA to the point that the fan kicked on. It's not very scientific but, the fan kicks in when the heatsink gets warm now. I'm sure someone else will provide a much more scientific method but, that has worked for me. 73 de John - KC4KGU K2/100 #2490 +++++++++++++++++ Date: Wed, 06 Nov 2002 01:44:43 -0600 To: K9OZ at aol.com, elecraft at mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] How hot is too hot >I got the KPA100 running with only minor troubleshooting, and it seems to be >running like a champ. Gave it a good workout in SS last weekend. But can't >find anything on how hot is too hot on the heat sink. > >If I wait for fan to come on (whether set on normal or low/high) it seems >like the sink gets pretty warm to the touch before the fan kicks in. The fan >seems to cool it, hold down heat well. So for the contest I just switched it >to High fan and let it run. > >But tonight in a casual QSO, top was hot again before fan kicked in. Is this >normal, or should I be checking things twice? As I recall, general rule of thumb: If you can place your hand (finger) on the heatsink and leave it there for 5-6 seconds without screaming, it's getting 'warm'. 73, Tom N0SS ++++++++++++++++ Date: Wed, 06 Nov 2002 07:55:40 -0500 To: Tom Hammond =?iso-8859-1?Q?N=D8SS?= From: Charles Greene Subject: Re: [Elecraft] How hot is too hot Cc: elecraft at mailman.qth.net Hi, Take it from an old Navy steam engineer. If you can keep your hand on an object, it is less than 140 deg F. Whatever that means for the KPA100 and the hand test. Got to be scientific about these things. :-) ++++++++++++++++++ From: "Don Brown" To: , Cc: "Elecraft" Subject: Re: [Elecraft] How hot is too hot Date: Wed, 6 Nov 2002 07:53:41 -0600 Hi I do this adjustment with a Fluke temperature meter and a K-type thermoco= uple placed on the mounting screw of Q3. This transistor is the temperatu= re sensor for the PA transistors/heatsink. I then adjust the CAL temp to = the same reading as the meter in degrees C. =20 If you don't have a temperature meter you could run the PA a little into = a dummy load until the heatsink is a little warm then lay a small medical= thermometer on the heatsink for 3 or 4 minutes take the reading and conv= ert to degrees C. C=3D(F-32)*.5556) =20 You could also turn off the K2/100 and let it settle to room temperature.= This may take about 1/2 to 1 hour. Assuming a comfortable room temperatu= re is 74 degrees F then set the CAL temp to 23 degrees C the first thing = after turning on the K2/100 this should get reasonably close to the right= setting. Don Brown KD5NDB +++++++++++++++ From: w7qhd at webtv.net (Kurt Cramer) Date: Wed, 6 Nov 2002 09:58:33 -0700 (MST) To: g3pjt at whsmithnet.co.uk (g3pjt) Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] re osc problem on kpa100 Bob, I got around to looking into the pa osc problem on 17 meters. RFC10 had very short leads, so I just tried a ground connection from the pa shield to one of the screws holding the SO-239. It worked! I used a long solder lug that I had in the junk box. I put it under the nut at the SO-239 and it also fit under the screw head of the corner stand-off of the pa shield. No more than 3/4" long. Thanks for the info and the pictures. That gave me the confidence to try something. 73, Kurt W7QHD (since 1951) web page: http://W7QHD.tripod.com ++++++++++++++++++ Reply-To: From: "J. Edward (Ed) Muns" To: "Elecraft" Date: Tue, 26 Nov 2002 12:19:37 -0800 Subject: [Elecraft] KPA100 PA Bias Adjustment Step In the recent ARRL Sweepstakes, I used my K2/100 for the first time on SSB since I built the KPA100 back in May 2002. The only thing that gets me on SSB is the Northern California Contest Club's plea to members for maximizing the club score for certain contests. Much to my chagrin, I got immediate reports that I had "RF feedback" in my audio, or "distortion", or "narrow audio". I quickly went off-the-air and ran Spectrogram to move my SSB BFO settings to a better, I thought, position. I went into the Sweepstakes and never heard another comment until right at the end when W6TER worked me and remarked that "your audio is terrible". Not what I wanted to hear. The end result of my troubleshooting is that my KPA100 PA bias was set at 70 mA instead of the specified 400 mA. However, this mistake was very deliberate on my part. I'm guilty of mis-interpreting the 6th step on page 47 of the KPA100 manual (Appendix G, Rev. A). Maybe the following explanation will help others avoid the same issue. When I built my KPA100 field test unit back in May 2002, I had a question about this step and mistakenly made a very literal (but, wrong) interpretation of the wording. To give the builder background, the manual explains that the base K2 draws 200-400 mA in receive mode. The addition of the KPA100 adds another approximate 200 mA. The PA transistor bias is to be set at 400 mA, so this instruction step is aimed at having the builder set R6, PA BIAS, on the KPA100 board to the sum of all these currents, or around 900 mA. (Each builder is to measure his power supply currents, do the addition, and come up with his own unique current setting.) Here is a comparison of the correct, and my original incorrect, calculation: Power Supply current components: CORRECT INCORRECT K2 RX 200-400 disregarded! KPA100 fan 50 50 KPA100 T-R switch 150 150 KPA100 PA bias 400 400 ------- ------- 800-1000 600 My mistake was interpreting this instruction step as follows: "Set the POWER control for 11 watts. The current should increase by about 200 mA (150 mA for the KPA100 T-R switch, and 50 mA for the fan, running at low speed). Record this current: _____mA. Add 400 mA (200 mA per power transistor) to this to determine the target reading for the bias-setting step below: _____mA." I thought "... this current ..." in the third sentence was "The current ..." in the preceding sentence. WRONG! "... this current ..." is the TOTAL current reading of the base K2's receive current and this 200 mA increase described in the preceding sentence. Needless to say, biasing the PA transistors at 35 mA. each vs. the specified 200 mA. meant that my SSB signal was probably operating the PA transistors in the non-linear portion of their curve. On CW, no problem was noticed, and as Eric pointed out, on CW there is enough filtering of any harmonics generated that the output is OK. On SSB, though, it was another story! I think I've terrorized Wayne enough over this that he'll probably add to the KPA100 errata sheet to help any future builders who possess my particular logic pattern irregularities! 73, Ed - W0YK +++++++++++++++++ Date: Fri, 13 Dec 2002 17:24:19 -0800 From: Wayne Burdick Organization: Elecraft To: Elecraft Subject: [Elecraft] reminder to K2/100 owners: tighten PA hardware If you've built a KPA100 option for your K2, and have operated it for a while, don't forget to re-tighten the PA hardware as described in the KPA100 manual. This hardware *will* loosen slightly over time (about 1/8th turn), worsening the thermal bond between the transistors and the heat sink. You should only have to do this re-tightening step once, ideally after the first week or two of use. 73, Wayne N6KR +++++++++++++++++ Date: Sun, 15 Dec 2002 07:02:39 -0800 From: Phil Wheeler Organization: Outstanding To: Unifiedtx at aol.com Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] Dressing Up the Back of the K2/100 Unifiedtx at aol.com wrote: >Has anybody found some nice looking caps to cover the unused BNC connectors >on the back of the K2, KPA100 and the KAT100-1, replacing the black plastic >ones. > I think Elecrat has them. When you build certain options, there are unused BNC prots and I believe I received covers with one or more options since I do have one of more on the back of my K2. I do not recall purchasing them elsewhere -- but it is possible I did (live in LA with lots of electronics shops around) 73, Phil ++++++++++++++++ From: Kevin Rock To: Brian Machesney , "Philip L. Carter" Cc: "'elecraft'" Date: Tue, 24 Dec 2002 18:23:01 -0700 Subject: Re: [Elecraft] Help! KPA100 rear panel assembly I did that too. Nothing fit correctly :( Once I determined which side to put the jack on all went well. Kevin. KD5ONS 12/24/2002 5:21:04 PM, "Philip L. Carter" wrote: >You may have the antenna jack on the wrong side of the read panel. I >did at first... > >Phil >wd8qwr #370 +++++++++++++++++ Date: Mon, 06 Jan 2003 14:35:10 -0800 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: Andrey Stoev Cc: "'elecraft'" Subject: Re: [Elecraft] Thermal Interface, pads vs. grease question? Hi Andrey, We officially recommend that you use the thermal pads supplied with the KPA100 kit instead of grease. They consist of a very efficient thermally conductive compound coated on both sides a a very thin aluminum sheet. The compound reflows when the transistors get hot the first time and fills all of the small air gaps between the devices and the heatsink. It is very effective and provides a better thermal bond in most cases than manual application of thermal grease. 73, Eric WA6HHQ Elecraft ========= Andrey Stoev wrote: > > Hi, > Soon I will be finishing up my KPA100, just waiting for some missing parts. > My question is about the thermal pads used for the transistors in the final stage (Q1 and Q2). > The kit comes with some thermal pads to serve as a thermal interface between the transistors and the heatsink. My question is: can i use a thermal grease, such as Arctic Silver III ( http://www.arcticsilver.com/) instead of thermal pads. As far as i know Arctic Silver contains pure micronized silver and it has very low thermal resistance and very high thermal conductivity (>9.0 W/m-K - way better than the zinc oxide grease ("the white stuff") which is ~0.735 W/m-K) I asume, it would be better thermal conductor than the supplied pads. The electric conductivity of the compound should not be a problem, since the emiter ciruit is grounded anyway. Better thermal interface will improve the heat transffer and will provide the PA transistors with better cooling and more accurate temperature readings from Q3. Is there any potential problems or something that i am overlooking and is it safe to experiment with it? > > Thanks and 73s +++++++++++++++++ Date: Mon, 06 Jan 2003 15:02:34 -0800 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: elecraft at mailman.qth.net Subject: Re: [Elecraft] Thermal Interface, pads vs. grease question? On the KPA100 the transistor flanges may be connected to ground so the thermal pads we use are not insulating. On the K2 the PA transistor's flange is connected to the collector and is not at ground potential, so we use insulated thermal pads there. 73, Eric WA6HHQ Elecraft --- Rich Lentz wrote: > > Doesn't the thermal pad also provide electrical insulation? After getting a > low resistance when installing a MOD I discovered the problem was a small > sliver of metal inbeded in the pad. Thermal grease would not have this > property without an insulator. ++++++++++++++++++ Reply-To: "Steve & Anne Ray" From: "Steve & Anne Ray" To: "Elecraft" Date: Sun, 2 Feb 2003 12:50:50 -0500 Subject: [Elecraft] Erratic Tuning KAT100 and rerouting cables. I finished up my KAT100 Friday night, 31 Jan, and it is working great on all bands. I discovered however that on 17 meters the tuning was erratic and it seemed to lock up. I had not installed the bypass cap on pin 7 of the interface cable where it plugged into the K2. This condition even existed in QRP down to about 2 watts. Yet, it did not exist on any other bands in either the QRP or QRO mode. It also existed when I fed the rig into a 50 ohm dummy load. I found that the rf cable between my K2 and the Amp and tuner which are in a EC2 case were quite close together. I rerouted the rf cable and solved the problem. This morning I bypassed pin 7 of the interface cable and completely solved the problem. So if you are having some strange conditions, rather then disconnecting the pin 7 to see if it cures the problem, try rerouting the cables. If it does then put the bypass cap in. I am really enjoying the KPA100 and the KAT100 in the EC2 case, it makes a nice combination and getting excellent reports. Steve Ray K4JPN ex K1VKW EM82ep Warner Robins GA Elecraft K2 1422 & KPA-100 Heath Fan HW-101, HW-8 ++++++++++++++++++++ Reply-To: "Steve & Anne Ray" From: "Steve & Anne Ray" To: "Elecraft" , "Daniel L Brinneman" Date: Sun, 2 Feb 2003 20:51:34 -0500 Subject: [Elecraft] Re: KAT100 and KPA100 together in the EC2 case (PIX) Nothing special about the hookup, just like the pictures in the article on putting the KPA100 and KAT100 in the EC2 case. The condition I had was that the cable from the K2 to where it hooks into the KAT100 was crossing over the computer cable. Simply running the rf cable a little different solved the problem. This morning I put in the .01 cap in the plug to the K2 and it also solved the problem. Why this was happening only on 17 meters is beyond me, but then again I never liked Maxwell Equations in Engineering School. 72, Steve Ray K4JPN ex K1VKW EM82ep Warner Robins GA Elecraft K2 1422 & KPA-100 Heath Fan HW-101, HW-8 +++++++++++++++++++++ From: "Don Brown" To: "Jibeji" , Subject: Re: [Elecraft] KPA100 Power question Date: Sat, 15 Mar 2003 09:04:46 -0600 Hi No. You do not have R26 set right. Assuming your Bird is accurate you need to make the K2 wattmeter read the same as the Bird. Adjust the K2 power for 50 watts as indicated on the bird then adjust R26 until the K2 display reads 50 watts. Readjust the power pot slightly after each change of R26 so the MPU will reread the power out. If everything looks good check at 100 watts and readjust R26 a little to bring the meters into agreement. Make very tiny adjustments of R26 on the order of only 1 or 2 degrees. Once R26 is set, adjust R27 to about 20% more clockwise than R26. Just eyeball it or, with the power off, measure R26 with an ohmmeter and set R27 to 20% higher resistance. Don Brown KD5NDB ----- Original Message ----- From: "Jibeji" To: Sent: Saturday, March 15, 2003 8:47 AM Subject: [Elecraft] KPA100 Power question > Hi. > I have just finished to build the KPA100 option. All tests were succesfully > passed but, at full power range, my Bird indicates only 75 W instead of the > 110 W shown by the internal Powermeter. > Is it normal ? > Thanks, 73 > -- > F8DQL - UFT 1116 > K2/100 #3249 ++++++++++++++++++ Date: Wed, 28 May 2003 16:11:33 -0700 From: Wayne Burdick Organization: Elecraft To: Elecraft Subject: [Elecraft] reminder to K2/100 owners: tighten PA hardware (one time) If you've built a KPA100 option for your K2, and have now operated it for a while, don't forget to re-tighten the PA hardware as described in the KPA100 manual. This hardware *will* loosen slightly over time (about 1/8th turn), worsening the thermal bond between the transistors and the heat sink. You should only have to do this re-tightening step once, ideally after the first week or two of use. 73, Wayne N6KR ++++++++++++++++ Reply-To: "John Veach" From: "John Veach" To: Date: Fri, 30 May 2003 07:33:09 -0600 Subject: [Elecraft] R28 on the KPA100 I have completed the first phase of building my KPA100 and was also perplexed at the very first step, R28. After pondering this for a while, I just assumed the outline on the board did not represent the actual component size. I sure did spend a lot of time looking for a larger resistor though! I am now ready to do the initial testing, but am waiting for one of the miniature RF chokes that was missing from my kit. I've built the K2, the SSB board, the 160m board and the qrp ATU and this is the first time I have found a part missing from the inventory. I do find that not having the resistors laid out in order like the K2 slowed me down a bit, but perhaps that is a good thing. Now on to winding all those toroids. John KE4D www.TheRollingHome.com Cannonville, UT for the summer ++++++++++++++++ Date: Tue, 03 Jun 2003 08:44:00 -0700 From: Wayne Burdick Organization: Elecraft To: Bob Nielsen Cc: elecraft at mailman.qth.net Subject: [Elecraft] Re: KPA100 assembly question Bob, All seven milled standoffs in the heatsink should be at the same level. The additional surrounding mill depth in the part of the heatsink that you mentioned is taken into account. So there should be no gap between the standoffs and the PCB at any point. If there is, it must be due to very slight warpage of the PC board, which is unavoidable in boards of this size. So you should not need a washer. Remember to put the two shorter standoffs at the front edge of the heatsink, corresponding with the reduced height of the shield in this area. This is explained in the instructions. 73, Wayne N6KR Bob Nielsen wrote: > > I inserted the setscrews into the heatsink and threaded the standoffs > onto five of them. The one near the back center is at a lower level > than the others, since the portion of the heatsink where this is > installed has a section milled below the rest of the heatsink. When > the pc board is installed it rests on the other standoffs but there is > a ~.025 gap between the board and the standoff at that position. Is > this correct? Should a washer be installed to support the board? +++++++++++++++ Date: Tue, 03 Jun 2003 09:30:39 -0700 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: Bob Nielsen Cc: Wayne Burdick , elecraft at mailman.qth.net Subject: Re: [Elecraft] Re: KPA100 assembly question Hi Bob, The spot you mention is a result of milling the heatsink surface slightly at that point to compensate for tolerance build up in the overall flatness of the heatsink when it is extruded. There still will be slight variations in the flatness of the heatsink mounting locations, but they should not be a problem. Its OK to slightly flex the board on installation. .025" on a PC board the size of the KPA100's is not a problem. 73, Eric WA6HHQ Bob Nielsen wrote: > Wayne, > > The manual mentions shorter standoffs at the front edge but those are > where the heat shield is installed. I am referring to an earlier step > on page 35 where the five 3/8" standoffs which support the PC board on > the heatsink are installed (there are also two standoffs which are part > of the pedestal). The heatsink has a milled area at the back where the > standoff nearest the fan is mounted which is ~.025 or so below the rest > of the heatsink, so that standoff is lower than the others. > > Bob > ++++++++++++++++++ Date: Tue, 3 Jun 2003 09:48:52 -0700 From: Bob Nielsen To: Eric Swartz WA6HHQ - Elecraft Cc: Wayne Burdick , elecraft at mailman.qth.net Subject: Re: [Elecraft] Re: KPA100 assembly question Thanks for the explanation Eric. Everything fits so well that I wanted to ask before proceeding, in case I had misunderstood the manual. 73, Bob, N7XY +++++++++++++++++ Date: Tue, 03 Jun 2003 14:26:31 -0500 To: "John Cooper" , From: Tom Hammond Subject: Re: [Elecraft] kpa100 power transistor Hi John: >i just put in the power transistors and like the manual said my soldering >wasnt hot enough to do it since its a fine tip low wattage. so i just >used 2 soldering irons on each leg of the transistors for a few seconds >each. wondering how susceptible to heat these guys are. If you didn't lift the pads of the PC board, you (and the transistors) in good shape!!! For soldering heavy PC board pads, and especially those around the KPA100 transistors, I suggest using a heavy-tipped iron or even a good soldering GUN (e.g. Weller). Wen soldering guns get too hot(!!!) and can damage PC board lands if not carefully controlled. When I'm soldering to large, heavy lands, I change tips on my T/C iron, and go to the largest (highest mass) tip I can find... usually a 1/4" wide tip. Good luck, Tom Hammond N0SS ++++++++++++++++