(no subject)
Locked
 
|
If this is not appropriate, please let me know.
A am forwarding this to the group in the hopes of getting some additional help and to perhaps decrease Gary's load a bit. I am not getting any significant output from my K2 in Alignment III. I've replaced Q7 and Q8 (broke the leads), rechecked T1-T4 and resoldered. Found some missing parts and corrected. I'm hoping there's something OBVIOUS I'm missing. John AB8WH = Gary Here are the (partial) results. I'm afraid I really don't have the BIG PICTURE When using the RF probe, my DVM is set to VDC On May 22, 2006, at 8:19 PM, Gary Surrency wrote: The PA transistors should be OK as long as you did not transmit with the PA heat sink removed, and none of the leads are broken off. Always replace both PA transistors at the same time if one of them fails, overheats, or stays cold during transmit, or fails the base bias test of 0VDC in receive, not more than 0.62 to 0.65VDC in transmit. 0 VDC in Receive...3 mV in Tx Both PA transistors should get warm around their mounting hardware on the heat sink after a few seconds in transmit, and both need to be healthy in order operate properly in the push-pull PA stage. They feel a little warm after about 10sec Q22 is supposed to be warm after the rig has been on for a while. It is NOT associated with transmitting - only with receiving. Lack of RF output on all bands usually means the PAs are damaged, or there is a problem with some of the parts around Q5-Q8, T1-T4. Doing RF voltage tests is the best way to narrow down where the problem is: Here are useful measurements to take when the rig is in transmit. All measurements taken at 7100kHz with a 100MHz oscilloscope, at maximum TX output unless otherwise specified. anode side of D7 220mVpp In TX, D7 has 8.11 VDC on its anode about 220 mv on RF 7.88 VDC cathode side of D7 200mVpp In TX, D7 has 7.49 VDC on its cathode about 200 mv on RF 7.25 VDC jumper W6 250mVpp Note: L1 and L2 *must be peaked, or you will not get this. .360 V on RF collector of Q5 500-600mVpp Q6 has 12.58 VDC at minimum output, 11.9 VDC at full drive How can I measure Leads of Q5 when I need to remove sink to access? base of Q6 200mVpp Near sine wave. 800mVDC to 1.1VDC 160 mV collector of Q6 6-10Vpp Nice sine wave. 13.6-12.5VDC, 0.1 to 15W out. 3.3 V base of Q7/Q8 2Vpp some distortion is normal here. 0.620 to 0.650 VDC Q7 .62 Q8 .65 VDC RF probe: .03 V and dropping over time collector of Q7/Q8 21-25Vpp also distorted here at full power. 13.6 VDC 8 to 8.5 VDC jumper W1 70-80Vpp clean sine wave 40V antenna jack 70-80Vpp clean sine wave mVpp = RF millivolts peak to peak Vpp = RF volts peak to peak NOTE: The RF probe in the kit will show only about 35% of these pk- pk voltages as it reads rms voltage, not peak to peak. Do not use the probe on the antenna RF output or the diode detector in it may be damaged. I hope this info helps you to track down where the problem is. -- 73, Gary AB7MY ========= _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
John,
Check the RF Voltages as Gary has indicated - you can reach the collector of Q5 easily, the case is also connected to the collector. Once you have discovered the stage where the RF voltage is significantly lower than the values Gary has indicated, you can identify the failing stage and look in detail at the associated components or the failure. Once you can tell us the failing stage, we can help further from there. 73, Don W3FPR -----Original Message----- A am forwarding this to the group in the hopes of getting some additional help and to perhaps decrease Gary's load a bit. I am not getting any significant output from my K2 in Alignment III. I've replaced Q7 and Q8 (broke the leads), rechecked T1-T4 and resoldered. Found some missing parts and corrected. I'm hoping there's something OBVIOUS I'm missing. John AB8WH = Gary Here are the (partial) results. I'm afraid I really don't have the BIG PICTURE When using the RF probe, my DVM is set to VDC On May 22, 2006, at 8:19 PM, Gary Surrency wrote: The PA transistors should be OK as long as you did not transmit with the PA heat sink removed, and none of the leads are broken off. Always replace both PA transistors at the same time if one of them fails, overheats, or stays cold during transmit, or fails the base bias test of 0VDC in receive, not more than 0.62 to 0.65VDC in transmit. 0 VDC in Receive...3 mV in Tx Both PA transistors should get warm around their mounting hardware on the heat sink after a few seconds in transmit, and both need to be healthy in order operate properly in the push-pull PA stage. They feel a little warm after about 10sec Q22 is supposed to be warm after the rig has been on for a while. It is NOT associated with transmitting - only with receiving. Lack of RF output on all bands usually means the PAs are damaged, or there is a problem with some of the parts around Q5-Q8, T1-T4. Doing RF voltage tests is the best way to narrow down where the problem is: Here are useful measurements to take when the rig is in transmit. All measurements taken at 7100kHz with a 100MHz oscilloscope, at maximum TX output unless otherwise specified. anode side of D7 220mVpp In TX, D7 has 8.11 VDC on its anode about 220 mv on RF 7.88 VDC cathode side of D7 200mVpp In TX, D7 has 7.49 VDC on its cathode about 200 mv on RF 7.25 VDC jumper W6 250mVpp Note: L1 and L2 *must be peaked, or you will not get this. .360 V on RF collector of Q5 500-600mVpp Q6 has 12.58 VDC at minimum output, 11.9 VDC at full drive How can I measure Leads of Q5 when I need to remove sink to access? base of Q6 200mVpp Near sine wave. 800mVDC to 1.1VDC 160 mV collector of Q6 6-10Vpp Nice sine wave. 13.6-12.5VDC, 0.1 to 15W out. 3.3 V base of Q7/Q8 2Vpp some distortion is normal here. 0.620 to 0.650 VDC Q7 .62 Q8 .65 VDC RF probe: .03 V and dropping over time collector of Q7/Q8 21-25Vpp also distorted here at full power. 13.6 VDC 8 to 8.5 VDC jumper W1 70-80Vpp clean sine wave 40V antenna jack 70-80Vpp clean sine wave mVpp = RF millivolts peak to peak Vpp = RF volts peak to peak NOTE: The RF probe in the kit will show only about 35% of these pk- pk voltages as it reads rms voltage, not peak to peak. Do not use the probe on the antenna RF output or the diode detector in it may be damaged. I hope this info helps you to track down where the problem is. -- 73, Gary AB7MY ========= _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.392 / Virus Database: 268.6.1/344 - Release Date: 5/19/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.392 / Virus Database: 268.7.0/345 - Release Date: 5/22/2006 _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
«
Return to Elecraft
|
1 view|%1 views
| Free forum by Nabble | Edit this page |