[Elecraft] KSB2 problem status: befuddled

Mon Feb 21 23:56:49 EST 2005

Neal,

Taking things in reverse order - go ahead and put the Noise Blanker itself
back in rather than the 6 dB pad resistors. It will only affect the receive
path and not the Transmit path.

OK - your current draw at a constant 10 Watts output looks just fine to me.
It is a bit unusual that your minimum current draw for 10 watts out is at 20
meters - usually that will occur at 40 or 30 meters - but this does not look
like a real problem to me (actually it indicates better efficiency than
normal on the higher bands).

so now that still leaves us with the original problem of excessive current
draw in SSB mode.  Actually something is 'fishy' here, because an SSB signal
with no audio will result in very little output power (and quite low current
draw).  So my thinking now is that you do not have the SSB balance set
properly - or there is something incorrect on the KSB2 board.  I know it is
difficult to do, but do look again - particularly at the balanced modulator
and those things shown around it in the schematic.  It does now seem that
your problems are coming from the KSB2.  Just as a wild guess I must ask -
did you remove C167 from the RF board when installing the KSB2?  If you fail
to remove it, that alone could explain the conditions you are seeing.

73,
Don W3FPR

> -----Original Message-----
>
> Hi all,
>
> Thanks for giving some ideas!
>
> I checked the resistors on the bottom of the ssb board, they are all
> correct. I must say that trying to identify parts on the top of the
> board is a real challenge, its so stuffed that its almost impossible!
>
> Don, I redid the output  amperage at 10 watts:
> 80 - 2.68
> 40 - 2.72
> 30 - 2.28
> 20 - 1.96
> 17 - 2.42
> 15 - 2.50
> 12 - 2.24
> 10 - 2.16
>
> At 10 watts on 40, the voltage on rx is 13.5 on tx its 12.9.
>
> The group is right, I did not notice the power output on lower than 17m
> (which is 15 watts). On 15 through 10, highest output is 13.3 watts.
>
> Do I still need to investigate the 40m current usage?
>
> Do I need to replace the 3 resistors and jumper that I pulled out to
> eliminate the noise blanker module from the mix of things to
> investigate? I should have done one module and waited to know it worked
> before doing a second one!
>
> Neal
> On Feb 21, 2005, at 5:37 PM, W3FPR - Don Wilhelm wrote:
>
> > Neal,
> >
> > There may be nothing wrong with 40 meters after all - I had missed the
> > point
> > that you were setting the Power control to absolute max.  What is your
> > power
> > supply voltage?  13.8 volts is typical (13.6 on the display), and lower
> > power supply voltages will result in increased current draw.  What is
> > the
> > voltage when you are seeing a current of 3 amps or greater?
> >
> > I don't have a straightforward answer here.  Can it be that your
> > Carrier
> > Balance is not correctly set and you are really generating more RF
> > drive
> > with SSB than with CW?
> >
> > It is not really a fair comparison to compare current draw from band
> > to band
> > with the Power control set all the way clockwise.  Set it to 10 watts
> > and
> > check the current drawn for each band and both CW and SSB modes.
> > Actually SSB mode should draw little current without audio (if the
> > carrier is
> > balanced because there should be little or no RF output.
> >
> > 73,
> > Don W3FPR
> >
> >> -----Original Message-----
> >> Hi Don and all,
> >>
> >> I have spent the afternoon looking for where I could have made a
> >> mistake on the 40m LPF circuit. I didn't find any obvious ones, the
> >> toroids came from 'The guy de Toroids' but I counted them all anyway,
> >> and they are (luckily!) correct. Same for capacitors. Did the run of
> >> voltage checks and didn't notice anything really wrong.
> >>
> >> On cw, cranking the output knob to the max, the display readings for
> >> current are
> >> 80 3.22
> >> 40 3.36
> >> 30 2.84
> >> 20 2.38
> >> 17 3.08
> >> 15 2.84
> >> 12 2.62
> >> 10 2.42
> >>
> >> Output reads over 15 watts in all cases, usually abt 15.2. This reads
> >> pretty much the same with or without the SSB module installed.
> >>
> >> I take it from your comments that the fact that 40m is the highest cw
> >> reading, its indicative of something wrong. Looked at LPF and BPF
> >> areas. What should I expect on the amp readings, 2.35 on 40 and a
> >> gradual increase as I go towards 10m?
> >>
> >> I could reinstall the resistors and jumper and take out the noise
> >> blanker module as thats something put in yesterday, I take it that I
> >> need to do that if I want to test without it?
> >>
> >> I have boosted cal cur to 4.0 and still can get hi cur signal with
> >> output fully counterclockwise on both usb and lsb. I have been very
> >> happy working cw all week as it is (set the cal cur to 3.5 and it
> >> hasn't tripped yet).
> >>
> >> Any more ideas to look at?
> >>
> >>
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