Re: [Elecraft] KAT2 Power problem continued
Tom, The voltage at U4 pin 3 should be between 3 and 4 volts with 5 watts of power flowing through the wattmeter section of the KAT2 *and* with the FWD potentiometer (R1) fully clockwise. U4 is configured as a unity gain op amp, and the voltage at the output (pin 1)should be equal to the voltage at the input (pin 3). If it is not, check the soldering at U4. That should be true whether R6 is connected or not. If the conditions (and results) are not as stated, then as the manual states, check T1, D1, C50, C52 and R1 for good soldering. Count the turns on T1 to be certain you have not wound an extra turn. Is the power that you are passing through the KAT2 equal to 5 watts? How are you determining it? 73, Don W3FPR Tom Campie wrote: Still no solution for my power problem. Some correspondence with Gary at Elecraft has me back where I started. I removed R6 and saw 0V at the output of U4 but 2.5V on the input of U4 coming from U1 (pin 3 on U4). According to the testing in the manual this should be 3-4 volts with a requested power of 5 watts. I replaced R6 and now saw the 2.5V on the output of U4. This is still low obviously. I reflow'd all the solder joints in the SWR bridge as it suggests and this has not helped. I'm not sure where to look next. Tom W0EA __ 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
Re: [Elecraft] KAT2 Power problem continued
As per Gary's suggestion, I removed and rewound T1. I also reflowed all the joints in the SWR bridge and on U4. With R6 out, I still measure 0.0 V and with it in I'm still under 3 v. With it in, I read the same 2.4V as before. While I can't confirm the actual output power exactly, my MFJ tuner reads 5 watts when it is tuned (I don't have an RF probe or wattmeter yet - I'm getting the parts for the RF probe on Thursday) Could it be that U4 is bad? Amps like that don't break very easily. Still not sure where to look except U4 I guess... Tom On Tue, Jul 21, 2009 at 8:47 PM, Don Wilhelm w3...@embarqmail.com wrote: Tom, The voltage at U4 pin 3 should be between 3 and 4 volts with 5 watts of power flowing through the wattmeter section of the KAT2 *and* with the FWD potentiometer (R1) fully clockwise. U4 is configured as a unity gain op amp, and the voltage at the output (pin 1)should be equal to the voltage at the input (pin 3). If it is not, check the soldering at U4. That should be true whether R6 is connected or not. If the conditions (and results) are not as stated, then as the manual states, check T1, D1, C50, C52 and R1 for good soldering. Count the turns on T1 to be certain you have not wound an extra turn. Is the power that you are passing through the KAT2 equal to 5 watts? How are you determining it? 73, Don W3FPR Tom Campie wrote: Still no solution for my power problem. Some correspondence with Gary at Elecraft has me back where I started. I removed R6 and saw 0V at the output of U4 but 2.5V on the input of U4 coming from U1 (pin 3 on U4). According to the testing in the manual this should be 3-4 volts with a requested power of 5 watts. I replaced R6 and now saw the 2.5V on the output of U4. This is still low obviously. I reflow'd all the solder joints in the SWR bridge as it suggests and this has not helped. I'm not sure where to look next. Tom W0EA __ 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
Re: [Elecraft] KAT2 Power problem continued
Tom, With R6 out, and DC voltage on U4 pin 3, but 0 volts on U4 pin 1, you certainly can suspect that U4 is toast. Unless you have a solder bridge between U4 pins 2 and 3 *and* no connection between pins 1 and 2 - that would be 2 failures, and we normally expect only a single failure, so a bad U4 is the most likely answer. Do the test again, but this time measure the voltage at U4 pin 3. If that is different than the voltage at U4 pin 1, you have a problem with U4. (BTW, with 5 watts through the wattmeter, U4 pin 3 should measure between 3 and 4 volts). As I stated, U4 is a unity gain op amp, and the voltage at the output should be the same as the voltage at the input - that is the behavior of a working unity gain op amp. 73, Don W3FPR Tom Campie wrote: As per Gary's suggestion, I removed and rewound T1. I also reflowed all the joints in the SWR bridge and on U4. With R6 out, I still measure 0.0 V and with it in I'm still under 3 v. With it in, I read the same 2.4V as before. While I can't confirm the actual output power exactly, my MFJ tuner reads 5 watts when it is tuned (I don't have an RF probe or wattmeter yet - I'm getting the parts for the RF probe on Thursday) Could it be that U4 is bad? Amps like that don't break very easily. Still not sure where to look except U4 I guess... Tom On Tue, Jul 21, 2009 at 8:47 PM, Don Wilhelm w3...@embarqmail.com wrote: Tom, The voltage at U4 pin 3 should be between 3 and 4 volts with 5 watts of power flowing through the wattmeter section of the KAT2 *and* with the FWD potentiometer (R1) fully clockwise. U4 is configured as a unity gain op amp, and the voltage at the output (pin 1)should be equal to the voltage at the input (pin 3). If it is not, check the soldering at U4. That should be true whether R6 is connected or not. If the conditions (and results) are not as stated, then as the manual states, check T1, D1, C50, C52 and R1 for good soldering. Count the turns on T1 to be certain you have not wound an extra turn. Is the power that you are passing through the KAT2 equal to 5 watts? How are you determining it? 73, Don W3FPR Tom Campie wrote: Still no solution for my power problem. Some correspondence with Gary at Elecraft has me back where I started. I removed R6 and saw 0V at the output of U4 but 2.5V on the input of U4 coming from U1 (pin 3 on U4). According to the testing in the manual this should be 3-4 volts with a requested power of 5 watts. I replaced R6 and now saw the 2.5V on the output of U4. This is still low obviously. I reflow'd all the solder joints in the SWR bridge as it suggests and this has not helped. I'm not sure where to look next. Tom W0EA __ 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
