[Elecraft] Fw: K2 PA repair kit
Afternoon all: K2 #6272 is alive and well once again. Had a heck of a time getting the Q7 Q8 installed. Kept seeing a short to the heat sink. Turned out the corner of the tab on Q7 had a raised area and a slight sharp spot that was cutting through the thermal pad and shorting to the heat sink when the screw was tightened in the tab. Fixed that and all back together. 14.5 watts out on 40 meters into a dummy load with 2.42 amps draw. Much better. 10 meters shows 12 watts out with 3.15 amps draw. RX and TX working fine on all bands and the KAT2 doing it's job just fine. K60XV is not on the board at this time. Jumpers are in place for now. I did test voltage on the base of Q7 Q8. Both showing .63 volts while tuning. Now that the base K2 is up and running, it's time to tackle what ever ails my K60XV.. No solder bridges at 8T so I'm diggen in to see what gives. Thanks to all for your suggestions / help: 72Jerry N0JRN The K60XV should not reduce the base voltage at Q7 and Q8. BUT, since it is, remove the K60XV, put a jumper wire from pin 3 to pin 5 on J13 and stick the leads of a small value capacitor (4.7 pF is ideal) into pins 1 and 3 of J15. The K2 should operate normally except for 60 meters with that jumper/cap combination in place. The 0.64 volts is within range, even though it is a bit on the high side of what I normally like to see. As far as the K60XV problem, if your K2 has a serial number less than 3000, while you have the heat-sink removed, check the cut that was made on the 8T voltage line to pin 6 of J13 (see the K60XV installation instructions). If the cut was not complete it would interfere with the K2 power control as well as dragging the 8T voltage rail down. If your K2 is later than SN 3000, look for a solder blob making a bridge to the 8T voltage rail near J13 pin 6. 73, Don W3FPR __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
[Elecraft] Fw: K2 PA repair kit
- Original Message - From: n0jrn n0...@mchsi.com To: d...@w3fpr.com Sent: Sunday, January 24, 2010 7:53 PM Subject: Re: [Elecraft] K2 PA repair kit Thanks Don and all: R50 is already a 1/2 watt and is in good shape. I do have good desoldering equipment and now have Q7, Q8, Q11 Q13 off the board with no problems. Going back to the game and will follow your advise when reinstalling all transistors. Since the info I got from archives was incorrect, it was good that I ask the pros. Everyone have a great evening I'll see ya after the game 72 Jerry That is a 1.5 ohm resistor (1/2 watt) included with the kit and is to replace the emitter resistor of Q6 if needed - so check while you have the rear cover/heat-sink removed. If R50 is a 1/4 watt resistor, replace it with the 1/2 watt - if it is already a 1/2 watt, check to see if it is open - if so, replace it with the new one. If neither of these conditions apply, you have a 1.5 ohm resistor for your junk box. No need to remove T3 - that is simply one technique to remove the voltage from the collectors of Q7 and Q8 while troubleshooting the problem, but since you will be removing Q7 and Q8, there is no need to do anything with T3, just leave it in place. Be careful when removing components not to damage the thru-plated holes. If you do not have good de-soldering tools, cut the leads off the components and remove them from the holes one lead at a time - clean up the holes with solder wick, or if necessary a stainless steel needle or a wooden toothpick pushed into the hole while the solder is molten will clean them ni __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
