[Elecraft] K1 Acting up on 20M and 30M

[Don Wilhelm]

Jerry,

Looking at the schematic for the 4 band filter board and the K1, I do not
see anything that is common between 30 meters and 20 meters unless it is bad
relay points (but not likely K1).

I would suggest that you try to localize the trouble area.  Use a 'scope or
RF probe and compare the RF Voltage levels on the 4 band board at the input
to the Premix Bandpass filter (P1 pins 1 and 2), then the output of the
Premix Bandpass filter (P1 pin 6) - compare the 40 meter band with 30 meters
and the 20 meter band with 15/17 meters.

If you get a reasonable comparison at those points, go on to check the input
to the RF bandpass filter (P2 pin 1) and then the output of the RF Bandpass
filter (P2 pin 8).

At some point, you should see the RF Voltages are substantially different,
and you should look between the points with good levels and the one with bad
levels for the problem.

73,
Don W3FPR

> -----Original Message-----

>
> I have K1 SN950 with the 4 band module, Antenna Tuner and battery
> module.  It has been working like a champ for 3 years.  Now, it has
> decided it does not want to transmit on 20 meters and weakly on 30M.
>
> Radio works fine on all other bands.  Radio receives fine on all bands.
> When I attempt to tune on 20M, it fails to get a match, drops power to
> 0.1 (no matter how high I initially set it) and reports "Plo".  If I go
> in and check the SWR from the last tune (rx.x) it reports r0.0.  On 30M
> I do get a tune, I get a reported SWR of r9.9.
>
> If I check the antenna with a SWR Analyzer, it reports that the antenna
> is about 1.7 at the frequency I am trying to use on 20M and about 2.1 on
> 30M.
>
> I put a power meter in line with the radio:  It reports near zero output
> on 20M, about half power on 30M and appropriate power on all other
> bands.  If I swap out the antenna and put in a dummy load, the meter
> shows R6.3 and about half power on 30M, and Plo again and no measurable
> output on 20 M.
>
> I manually cycle through all the relays --- per the troubleshooting
> guide --- and they all are clicking --- none appear to be hung or dead.
>
> Any Ideas?
>
> Jerry - KG2JM
> K1 - 950
> K2 - 4550 (under construction)
>
>
>