Elecraft › [MM]

XG1 signal problem

Classic

List

Threaded

6 messages Options

Brian - N5BCN

XG1 signal problem

Hello all,

When attempting to calibrate my K2's S-meter with a XG1, I discovered the XG1 itself is having a problem. I verified this by connecting it to a working IC-7600.

The signal output on it, although heard, is very weak. Adjusted for on-frequency, the s-meter reads about S2 or S3. Touching the XG1 can get the signal up to about S4 or S5. Switching between 1 uV and 50 uV makes no apparent difference in signal strength on the s-meter.

Resistance checks on the XG1 and found some problems:

Resistance from the following junctions to ground:

U2, R1 = 50 k Ohms (should be 57-63 k Ohms)
C4, R3 = 50 k Ohms (should be 57-63 k Ohms)
R1, C1 = 54 k Ohms (should be 67-73 k Ohms)

Checked all component placements and solder joints, no obvious problems. Reheated all solder joints (twice now) just in case; no improvement.

My next step is to measure all the resistor and capacitor values.

Do these symptoms jump out anybody as something obvious (bad xtal or other component)? Any suggestions will be most appreciated.

73

Brian - N5BCN

Don Wilhelm-4

Re: XG1 signal problem

Brian,

Those resistances are close, but admittedly a bit on the low side - but
not enough to declare those the root of your problem.
Your description sounds like you get the 1 uV output no matter which
position the switch is in. The attenuator consisting of R6, R7 and R8
should be out of the circuit when in the 50 uV position.
Examine the schematic and check the switch for proper operation. The
schematic shows the switch in the 50 uV position. If the attenuator is
in all the time, you will have only a 1 uV signal level. If you are
having trouble following the schematic, then measure the resistance from
the junction of R4 and R5 to the junction of R6 and R8 when the switch
is in the 50 uV position - the resistance should be very high. If it is
not, look for solder splashes (and excess solder) or the possibility of
a bad switch.

73,
Don W3FPR

Brian - N5BCN wrote:

> Hello all,
>
> When attempting to calibrate my K2's S-meter with a XG1, I discovered the
> XG1 itself is having a problem. I verified this by connecting it to a
> working IC-7600.
>
> The signal output on it, although heard, is very weak. Adjusted for
> on-frequency, the s-meter reads about S2 or S3. Touching the XG1 can get
> the signal up to about S4 or S5. Switching between 1 uV and 50 uV makes no
> apparent difference in signal strength on the s-meter.
>
> Resistance checks on the XG1 and found some problems:
>
> Resistance from the following junctions to ground:
>
> U2, R1 = 50 k Ohms (should be 57-63 k Ohms)
> C4, R3 = 50 k Ohms (should be 57-63 k Ohms)
> R1, C1 = 54 k Ohms (should be 67-73 k Ohms)
>
> Checked all component placements and solder joints, no obvious problems.
> Reheated all solder joints (twice now) just in case; no improvement.
>
> My next step is to measure all the resistor and capacitor values.
>
> Do these symptoms jump out anybody as something obvious (bad xtal or other
> component)? Any suggestions will be most appreciated.
>
> 73
>
> Brian - N5BCN
>
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Brian - N5BCN

Re: XG1 signal problem

Hi Don,

The resistance from R4/R5 junction to R6/R8 junction with switch at 50 uV is about 104 Ohms. The value with the switch at 1 uV is 0.1 Ohms. 104 Ohms isn't "very high," perhaps a bad or dirty switch? No solder bridges visible around the switch.

Is there an easy way to clean it without removing it from the PCB?

Thanks.

Brian - N5BCN

Guy, K2AV

Re: XG1 signal problem

In reply to this post by Brian - N5BCN

Check to make sure you haven't transmitted into the XG1 and blown the
safety diode. You can easily remove it to see.

On Mon, Nov 23, 2009 at 4:40 PM, Brian - N5BCN <[hidden email]> wrote:

>
> Hello all,
>
> When attempting to calibrate my K2's S-meter with a XG1, I discovered the
> XG1 itself is having a problem. I verified this by connecting it to a
> working IC-7600.
>
> The signal output on it, although heard, is very weak. Adjusted for
> on-frequency, the s-meter reads about S2 or S3. Touching the XG1 can get
> the signal up to about S4 or S5. Switching between 1 uV and 50 uV makes no
> apparent difference in signal strength on the s-meter.
>
> Resistance checks on the XG1 and found some problems:
>
> Resistance from the following junctions to ground:
>
> U2, R1 = 50 k Ohms (should be 57-63 k Ohms)
> C4, R3 = 50 k Ohms (should be 57-63 k Ohms)
> R1, C1 = 54 k Ohms (should be 67-73 k Ohms)
>
> Checked all component placements and solder joints, no obvious problems.
> Reheated all solder joints (twice now) just in case; no improvement.
>
> My next step is to measure all the resistor and capacitor values.
>
> Do these symptoms jump out anybody as something obvious (bad xtal or other
> component)? Any suggestions will be most appreciated.
>
> 73
>
> Brian - N5BCN
>
> -----
> K2 #6800 KSB2 KAT2 KIO2 KNB2
> --
> View this message in context: http://n2.nabble.com/XG1-signal-problem-tp4054195p4054195.html
> Sent from the [MM] mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Don Wilhelm-4

Re: XG1 signal problem

In reply to this post by Brian - N5BCN

Brian,

I would advocate removing the switch from the PC board and see if the
resistance goes higher - in theory, it should be infinite.
I don't know of an easy way - sorry. It may be the switch, or it could
be the diodes in the output, but something is not right if you measured
104 ohms with the switch in the 50 uV position.

73,
Don W3FPR

Brian - N5BCN wrote:

> Hi Don,
>
> The resistance from R4/R5 junction to R6/R8 junction with switch at 50 uV is
> about 104 Ohms. The value with the switch at 1 uV is 0.1 Ohms. 104 Ohms
> isn't "very high," perhaps a bad or dirty switch? No solder bridges visible
> around the switch.
>
> Is there an easy way to clean it without removing it from the PCB?
>
> Thanks.
>
> Brian - N5BCN
>
> -----
> K2 #6800 KSB2 KAT2 KIO2 KNB2
>
>

Jim HaRRIS

Re: XG1 signal problem

In reply to this post by Brian - N5BCN

Brian,

I had a similar problem off and on with my XG1 for 2-3 years. While recently calibrating the S meter in my new K3 it came to the point I could no longer use it. During troubleshooting as you did I found that tapping the case of X1 (crystal case) would cause the problem to come and go. I installed a replacement crystal from Elecraft and no longer had the problem. I also replaced the variable cap at the same time as a tiny piece of insulation was sticking out from the edge of the top metal plate under the adjustment screw.

If troubleshooting doesn't find another problem you might replace the crystal and/or variable cap to see what happens.

Have a good day and 73,

Jim, W0EM

Brian - N5BCN wrote

Hello all,

When attempting to calibrate my K2's S-meter with a XG1, I discovered the XG1 itself is having a problem. I verified this by connecting it to a working IC-7600.

The signal output on it, although heard, is very weak. Adjusted for on-frequency, the s-meter reads about S2 or S3. Touching the XG1 can get the signal up to about S4 or S5. Switching between 1 uV and 50 uV makes no apparent difference in signal strength on the s-meter.

Resistance checks on the XG1 and found some problems:

Resistance from the following junctions to ground:

U2, R1 = 50 k Ohms (should be 57-63 k Ohms)
C4, R3 = 50 k Ohms (should be 57-63 k Ohms)
R1, C1 = 54 k Ohms (should be 67-73 k Ohms)

Checked all component placements and solder joints, no obvious problems. Reheated all solder joints (twice now) just in case; no improvement.

My next step is to measure all the resistor and capacitor values.

Do these symptoms jump out anybody as something obvious (bad xtal or other component)? Any suggestions will be most appreciated.

73

Brian - N5BCN