[Elecraft] KX1 Low power output
With 13.0 volts at the input jack (from a bench supply), and 12.7 volts on the circuit board's + bus, I am only reading 1.4 watts maximum power output into a 50 ohm dummy load. I haven't found a problem using the troubleshooting guide, voltages at Q1, Q4, Q5, and Q6 are where they are supposed to be. T1 and L3 look OK to me - but if I'm a sub-par winder can that lead to lower output? I have the resistors for the higher power output mod, but I'm trying to rule out build problems first. Any additional ideas? Thanks, Chip __ 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] KX1 : low power
Hi all, I got a problem building my KX1: receive is OK, but transmit power is far too low (40 m 2W, 20 m 0,5 W with 13,5 V). Of course, I checked and double checked solders, solder bridges, components and values. BPF and LPF are OK as measured with RF generator and oscilloscope. Output waveform good. Frequency right. Transmit voltages are all OK, but Q7's transmit base voltage is minus 1,1 V (minus) instead of the requested plus 0,7 V. Resistances and other components Q7 circuit are OK? 6V_2T is + 5,5 V. Q7 replaced Q7 without. Any idea will be welcome ! 73 Luc/HB9ABB/F6HJO ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KX1 : low power
Luc, Before offering any specifics, can you make some RF Voltage measurements during a TUNE operation please? With that information, the problem can be isolated to one stage. Measure the following points for both 40 meters and 20 meters: Q1 gate Q1 Source Q4 base Q5 base Q5 collector Q6 base Q6 collector Please also tell us whether the voltages are peak to peak, zero to peak or RMS values. 73, Don W3FPR luc Favre wrote: Hi all, I got a problem building my KX1: receive is OK, but transmit power is far too low (40 m 2W, 20 m 0,5 W with 13,5 V). Of course, I checked and double checked solders, solder bridges, components and values. BPF and LPF are OK as measured with RF generator and oscilloscope. Output waveform good. Frequency right. Transmit voltages are all OK, but Q7's transmit base voltage is minus 1,1 V (minus) instead of the requested plus 0,7 V. Resistances and other components Q7 circuit are OK? 6V_2T is + 5,5 V. Q7 replaced Q7 without. Any idea will be welcome ! 73 Luc/HB9ABB/F6HJO ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KX1 : low power
Don, Thanks for your quick reply. Following values are Vrms made with Elecraft RF Probe and DDM. (7 MHz value/14 MHz value) Q1 gate : 0.17 / 0.16 Q1 Source : 0.11 / 0.18 Q4 base : 0.10 / 0.18 Q5 base : 0.9 / 1.1 Q5 collector : 4.7 / 6.0 Q6 base : 1.3 / 1.2 Q6 collector : 8.9 / 10.7 I suppose these values are quite consistent. Q5 collector values and Q6 base values seem to have the same relation betwenn them as the impedances (1:3). Am I right ? Thanks for your help. 73 Luc/F6HJO/HB9ABB ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KX1 : low power
Luc, Those RF voltages look normal until one reaches the Q5 collector. Changing R11 to 4.7 ohms (as in the power mod) will likely help, and you can increase R30 to 33 ohms (the remainder of the power mod) if changing R11 does not help enough. I am concerned because you indicated only 0.2 watts output on 20 meters - with 10.7 volts on the collector of Q6 you should have more output than 0.2 watts unless you also have a problem in the low pass filter area - check the number of turns on the toroids and check the values of C46, C47 and C54. Too many toroid turns can reduce the cutoff frequency of the 20 meter lowpass filter down into the 20 meter band and absorb a lot of the signal. When counting toroid turns, count each pass of the wire through the center of the core as 1 turn. 73, Don W3FPR luc Favre wrote: Don, Thanks for your quick reply. Following values are Vrms made with Elecraft RF Probe and DDM. (7 MHz value/14 MHz value) Q1 gate : 0.17 / 0.16 Q1 Source : 0.11 / 0.18 Q4 base : 0.10 / 0.18 Q5 base : 0.9 / 1.1 Q5 collector : 4.7 / 6.0 Q6 base : 1.3 / 1.2 Q6 collector : 8.9 / 10.7 I suppose these values are quite consistent. Q5 collector values and Q6 base values seem to have the same relation betwenn them as the impedances (1:3). Am I right ? Thanks for your help. 73 Luc/F6HJO/HB9ABB ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] KX1 - Low Power Output
Hello, I recently constructed a KX1 with the 30/80 meter option board, and I'm having problems with low power out on all bands except 80 meters. On a 13.8V power supply, I'm getting a hair over 3 watts, but only .5 - .7 watts on 20 meters (measured on a 50 Ohm dummy load). I checked the voltages on Q1, Q4, Q5 and Q6. Interesting, on 80 meters, the xmit voltages look OK, but on the other bands (e.g. 20 meters), the voltages on Q4 and Q5 are lower than expected. And just to make things interesting, when I check the voltage on Q1 (gate or drain) during XMIT, output power on 20 meters jumps up to about 2 watts. Actually touching the gate or drain with any metallic object increases TX power on 20 meters. I checked the current draw on 20 and 80 meters - current drain corresponds with TX power output. Any ideas? Thanks in advance! ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KX1 - Low Power Output
First, check the soldering carefully. If the solder connections look convex (like a ball on the component lead), the connection did not receive enough heat to flow the solder adequately onto the solder pad. If there is excess solder, wick it away and re-solder with a minimal amount of solder and adequate heat (at least 700 deg F). Watch the solder flow - if it flows out to a thin, almost invisible, edge on both the solder pad and the component lead, that is a good connection. The solder should be a bit concave - if it looks convex, it either has too much solder or did not receive enough heat or both. Check the low pass filter toroids (and T1 and L3 too) to be certain the leads have been well stripped and tinned - if the solder connection looks like a miniature volcano, you have a bad connection and the only cure is to remove the toroid, re-tin the leads and re-solder it - you cannot do a proper job of it while mounted on the board (I have tried many times). These two problems are the root cause for more than half of the repairs I do. It is seldom that I have to replace a part because it failed. If you have questions about how a good solder connection should look, check the drawings in the soldering tutorial on the Elecraft website (and now being shipped with many of the kits). 73, Don W3FPR Oliver Olsen wrote: Hello, I recently constructed a KX1 with the 30/80 meter option board, and I'm having problems with low power out on all bands except 80 meters. On a 13.8V power supply, I'm getting a hair over 3 watts, but only .5 - .7 watts on 20 meters (measured on a 50 Ohm dummy load). ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] kx1 low power output
can someone send me a link or guide to a comprehensive trouble-shooting tree for telling: 1) if my kx1 is producin less power output than it should 2) if so, what is the troubleshooting tree for figuring out why thanks ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] KX1 low power out
Greetings all; I have completed a KX1 with all options. Everything has gone great except I am seeing lower power output than it should be. From a 12.5V power supply I am seeing just around 2.5W measured with a scope into a dummy load (as well as other power meters). Likewise on fresh alkelines, seeing power less than spec. I have been through support from Elecraft (great by the way), but not finding any problems. All other operational tests are fine, bought a set of toroids from toroidguy just so I could do a turn-by-turn count. I am stumped... I am about ready to send it in to elecraft, but hate to spend the $$. I saw on the list a lengthy discussion about increasing R30 to 33 ohms. Is this common? Any other common low output power issues I should look at? 72 de Tim KD7JZ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
