+++++++++++++++++++++++ Entries about operating conditions and fans This describes the Elecraft Supplied fan and so other inspired OEM components... +++++++++++++++++++++++ Date: Sun, 15 Dec 2002 16:09:29 -0800 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: rondec at easystreet.com Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] KPA100 Fan Question Hi Ron, The air exits the case at the top of the K2/100 at the front between the heatsink fins. It does an excellent job of stabilizing the K2's internal temperature. If you still want to add auxilary cooling a 3" fan running at half speed placed on top of the heatsink (halfway to the rear and 2/3 to the right) pulling air up and away fromthe heatsink works well. Putting rubber stick on feet on the bottom of the fan will keep it in place and space it correctly for proper air flow. 73, Eric WA6HHQ +++++++++++++++++ Date: Mon, 16 Dec 2002 15:32:51 -0800 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: Don Brown Cc: "Wallace, Andy" , elecraft at mailman.qth.net Subject: Re: [Elecraft] Re:K2/100 Frequency Stability Please don't do this as it will draw HOT air across the heatsink fins into the cabinet. I designed the heat flow to pull cool air into the case from the rear and for it to exit through the front top heatsink fins and the other case openings. As I noted previously, the most efficient method of adding additional cooling is to move air across the heat sink fins. We have used this for several DXpeditions running high TX duty cycles in very hot environments and it runs the heatsink much cooler, resulting in cooler interior temperatures. If you want to add auxiliary cooling, a 3" 12V fan running at half speed placed on top of the heatsink (halfway to the rear and 2/3 to the right) pulling air up and away from the heatsink works well. Putting rubber stick on feet on the bottom of the fan will keep it in place and space it correctly for proper air flow. 73, Eric WA6HHQ ================ Don Brown wrote: > > Hi > > Maybe someone should try reversing the fan to see if pulling the hot air out > of the K2 would work better. It would make sense that if cool air was pulled > in through the slots in the bottom and over the RF board before it was > heated would keep the VFO cooler and at a more even temperature. > > Don Brown +++++++++++++++ Date: Sat, 21 Dec 2002 13:49:56 -0600 From: Lee Buller To: elecraft at mailman.qth.net Subject: [Elecraft] Fan Source for Auxiliary Fan The PC power supply fans are to big for my K2...or at least my tastes. I like the fans that are on the CPUs. These are the 50 mm fans and run fairly quiet. They will move enough air over the heat sink without blowing you out of the shack. You can lower the speed of the fan by putting a resistor in series and lowering the voltage to 10 volts. Some of these fans come with Molex connectors already and can be use quickly. I mounted two on a piece of aluminum angle stock and positioned them centered on each half of the heat sink. I put some felt self-stick pads on the aluminum stock so I would not scratch the finish on the K2. I dubbed it the K2 Kontest Kooler. You don't need the fan(s) at all for normal everyday use...but you start CQing and running rate...you will heat the K2 pretty well. Lee - K0WA ++++++++++++++++ Date: Sun, 12 Jan 2003 10:40:20 -0600 To: elecraft at mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: [Elecraft] A couple items of possible interest... Here are a couple items I'm tossing out in case someone might be interested. _______ Additional Cooling for the KPA100 Over the past month or so, several folks have posted messages about providing auxiliary cooling for their KPA100 heatsinks. And I believe a few web pages have shown some efforts as well. While the KPA100 heatsink probably only might require additional cooling if the KPA100 was fairly heavily used (e.g. long-winded exchanges or in a heavy-duty contest setting), there is no getting around the fact that heat from the KPA100 will eventually work its way into the K2 case and cause some warming of components, thus adding to any heat-related drift in the PLL. I too have built a cooling system for my KPA100. It is NOT pretty (in fact, Wayne took great glee in telling me how 'ugly' it was ), but the fact is that it does help to reduce the length of time the built-in KPA100 cooling fan must run, and it does seem to keep the interior of the K2 a bit cooler. If anyone is the least bit interested, I have a few pictures of my cooling enclosure available for viewing at: http://www.qsl.net/n0ss As I said, the enclosure it pretty ugly. In my defense, I built it a couple hours before last year's ARRL CW Sweepstakes and my intent was to get it built, and not to make it a work of art... that goal was realized... heheh. And I'm NOT trying to imply that my design is THE correct one. It's a design I've used for a number of years with decent success. If you have a better design, please post info about it here, on the reflector, so we all can benefit. _______ 73, Tom Hammond N0SS +++++++++++++++++++ From: "Don Brown" To: , Subject: Re: [Elecraft] KPA100 problem Date: Sun, 19 Jan 2003 12:10:58 -0600 Hi Don If you changed the firmware for the KAT100 and you got the INFO 201 message then all of your settings will need to be reset. This is because some of the look up tables were moved to the IOC IC to save space in the MPU. This required a hard reset so all of the factory defaults are loaded when first powered on. It sounds like the cal temp is not set up right. Q3 is the temperature sensor. If you used lock washers on the mounting screws they may have cracked the case on the transistor. I usually use a fiber washer on the screw so the lock washer does not dig into the transistor case. Anyway it would be a good time to check the screws on Q1 and Q2 to see if they need tightening. Another thing you may want to do is set R27 20% higher than R26 per the instructions in the KAT100. Measure the resistance from groung to the wiper of R26 and set R27 20% higher on its wiper. Don Brown KD5NDB ----- Original Message ----- From: To: Sent: Sunday, January 19, 2003 11:29 AM Subject: [Elecraft] KPA100 problem > For the last couple of days when I power up my K2/100, the fan begins running > immediately, and when I attempt to key the xmtr at more than 10 watts out, I > get a PA hot report as well as high swr. This is into a resonant antenna. > The problem occurs when the heat sink is cold to the touch. When I bring up > CAL tpa on the menu, the heat sink temp shows very high readings. I recently > changed out the firmware for the KAT 100. Do I need to do another temp. > calibration? If so, do I need to reset R6 fully counter-clockwise? Thanks > in advance for any suggestions. > > 73, > > Don W5EI +++++++++++++++++++ From: W5EI at cs.com Date: Mon, 20 Jan 2003 11:06:07 EST To: elecraft at mailman.qth.net Subject: [Elecraft] KPA100 Problem solved Took a close look at Q3, temp. sensor on the KPA100 board. Although I had retightened the mounting hardware two weeks after construction per Eric's suggestion, it had worked loose. It may be that I had not used enough torque, fearing overtightening because problems had been reported with the metal lockwasher damaging the case of Q3. In any event, after retightening the mounting hardware for Q3, the radio powered up this morning with the temperature reported via the CAL tpa menu as the correct ambient temperature. The fan (set to nor) no longer comes on when initially powering up the radio I think that the loosely mounted Q3 might have not been in sufficient contact with the heat sink to report a correct temperature reading. Thanks to all who replied to my question. 73, Don McNallen W5EI KPA100 #2478 +++++++++++++++++++++++ From: "Don Brown" To: , Subject: Re: [Elecraft] KPA100 Problem solved Date: Mon, 20 Jan 2003 16:32:45 -0600 Hi Don, Leo and all Maybe a little circuit description of the Temperature measuring circuit will help locate the problem. This circuit is similar to a temperature probe I worked on at Tektronix. If a constant current is forced through a transistor the base-emitter junction voltage will track fairly close to 10 mV change per 1 degree C. A large value (15K) resistor causes a constant current to flow in Q3 and U7B, Q4 buffers the base voltage of Q3 and forms a temperature regulated drive for the PA transistors. The base voltage at Q3 is also sent to an analog input on the KPA100 MPU. The firmware uses this voltage, that varies with temperature, to calculate the heat sink temperature. This works because Q3 is screwed to the heat sink so its base-emitter junction will be at the heat sink temperature. If Q3 was not screwed to the heat sink it would measure the ambient temperature in the K2. It should not read a very high temperature. I think the tightening of the screw may have flexed the board or the transistor, causing a bad connection somewhere to reconnect. The problem may come back. There is not enough current flowing in Q3 for it to self heat. What is worse if there is a problem in the temp measuring circuit it could over drive the bias on the PA transistors and cause the transistors to overheat. I had a KPA100 today I was working on with the bias misadjusted. If you keyed the mic the KPA100 would draw 10 amps without speaking into the mic. The normal draw should be a little less than 1 amp. After adjusting the bias everything was fine. I mention this because this is the symptom you would have if Q3 was not working or a bad connection in the temperature measuring circuit. If a split lock washer is used on Q3 and Q4 without a flat washer or fiber washer the split lock will sometimes crack the case of the transistor if tightened to much. I use a fiber washer like the ones used to mount the speaker on Q3 and Q4's mounting screws to cushion the transistors. Don Brown KD5NDB ----- Original Message ----- From: To: Sent: Monday, January 20, 2003 3:29 PM Subject: [Elecraft] KPA100 Problem solved > Leo, > > I don't believe anything was actually getting hot, because the PA hot message > appeared upon intial power-up when the heat sink was quite cold to the > touch. The high temp reading in the CAL tpa menu setting would also show an > extremely high temp reading even when the ambient temp. in my shack was only > 5 deg. C early in the morning. It's almost as if the erratic readings might > have been caused by a crack in the case of Q3, a possibility suggested by > Don, KD5NDB. I could not find such a problem when I looked at Q3; it was > quite loose however. > > 73, > > Don +++++++++++++++++