[Elecraft] ksb2 question

Wed Dec 10 13:55:45 EST 2008

Hi guys,
Trying to troubleshoot a KSB2 no Tx problem. I have exchanged a couple of ideas - suggestions with Don W3FPR and Garry AB7MY, but so far have not been able to find the culprit. I was wondering maybe someone else in the forum might have had a similar issue and or any suggestions ?

After receiving and installing the missing NE602 IC from my KSB2 module, I have the following problem with it:First, the initial testing and alignment of the SSB board went ok, as mentioned in pages 15-20 of the KSB2 manual. The BFO, OP1 filters and CAr ballance adjustment went fine, but there is no Tx signal output after trying to talk into a properly configured Kenwood MC-50 dynamic mic. The radio seems to go into the Tx mode after pressing the PTT, but no signal at any power level when talking to the mic. Before starting chasing the AF mic signal around with my oscilloscope, I did verify the correct placement of ICs, diodes, Caps etc on the KSB2 board, and did verify the presence of the correct voltages during SSB and CW Rx on the suggested per the manual page 23 diodes D9-D13. The voltages check of the ICs though, with the exception of U5, are mostly off the suggested values per the manual for all the remaining ICs, with the following most important differences:              measured (Rx/Tx)         suggested per manual (Rx/Tx)U1-3             4,8/4.8                       2.3/2.3U1-16           6.0/3.05                     6.0/5.4 U1-17           6.0/4.1                       6.0/5.6U1-21           5.8/0.06                      5.8/0.1U1-28           5.6/5.4                        5.6/2.4 U2-1             6.0/4.1                       6.0/5.6U2-5             2.5/2.5                       0.6/0.6U2-8             6.0/3.1                       6.0/5.4 U3-2             1.9/2.8                       2.5/2.5U3-3              2.9/3.8                      2.3/2.3U3-4              2.9/3.8                      1.7/1.7U3-5             4.4/4.4                        0.4/0.4U3-7             4.8/4.8                        2.2/2.2 U4-2             4.8/4.8                       2.2/2.2U4-3             2.5/2.5                       0.6/0.6U4-5             4.8/4.8                       2.2/2.2U4-6              5.5/0                         5.1/0 Also another strange behavior is that when trying to activate the VOX option, SPCH 0.2 comes temporarily on the screen, but then the K2 does not return to receive mode, and I can not cycle through the other delay VOX options. (It seems to be frozen in Tx, while the L or u (sb) indicator is normally flashing besides the frequency display, as it should. In order to return to receive, I have to turn the K2 off and then back on. Once, while having the mic disconnected, I could manage to have VOX activated properly (the K2 going back to Rx and being able to cycle through the VOX delay options) but it does not happen anymore..Based on the above measurements, I tend to believe that the U1 IC controller maybe is faulty????, even though I did observe proper antistatic handling precautions for its installation as I did for all the rest ICs. The rest of the K2, including the 100w PA seems to work ok when Txing in the TUNE mode, or Rx ing in all modes.

73 to all,
Marinos, sv9dru/ki4gin
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