Posted by
Don Wilhelm-3 on
Jul 06, 2006; 2:36pm
URL: http://elecraft.85.s1.nabble.com/Low-SSB-TX-power-on-K2-tp391810p391811.html
Cal,
First check the voltage on the collectors of Q2 and Q3 during transmit - you
should find close to 8 volts.
It sounds to me like you are not getting an adequate audio signal into the
balanced modulator (U4 on the KSB2 board).
Without some tool to observe the audio signal, that may be a tough thing to
de-bug. The DC levels on the points you mentioned do not have a direct
bearing on your problem.
One thing that you could do is check the components in the audio path - look
at the KSB2 schematic and find the components in the paths connecting to pin
4 and pin 7 of U3 on the KSB2 board. check all those for good soldering.
It is unlikely that your DMM will respond to AC signal levels comparable to
mic output voltages, so a tool (such as a 'scope) may be required if you
cannot find a problem by inspection.
The lack of D5 indicates that you have an older KSB2 board - that in itself
is not a problem, all else on the board is pretty much the same as the newer
boards.
73,
Don W3FPR
> -----Original Message-----
>
> I recently picked up an older K2 # 185. It's had all the
> important Elecraft-recommended performance mods and Alerts
> applied, including the "A to B" upgrade. The rig works FB on
> CW. I am disappointed with the SSB performance, even after using
> three mikes (and changed mike pin jumpers). I scanned the email
> reflector and decided to do voltage checks of the ICs and diodes
> on the SSB board. The SSB board is Rev. C. There is no reading
> on the S-meter when I transmit, and no reading on ALC. I do get
> a very weak signal when I used each of the three mikes and
> listened on my other rig. I also transmitted PSK and again get a
> weak signal, however, the IMD was -23. A couple of hams within 5
> miles said they heard me on 20 meter SSB, but just at the noise
> level. Another ham who lives about 10 miles away could not hear
> me, but I heard him calling me. Firmware is 2.01H and IOC 1.02.
>
>
> Can someone provide some direction as to my next step? My only
> diagnostic tool, outside of the K2 built-ins, is a DMM. My
> background is in accouting and risk management, unfortunately not
> in eletronics.
>
>
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