[Elecraft] K3: Main RX gone deaf

[Udo Langenohl - DK5YA]

Gents,

I had another test session today with my K3 and here's what I've done 
and what happened:

1. I've checked all the test points recommended by Elecraft. No issue 
found, all stages are working, there's noise increasing on each test 
point at the Main RX.

2. Fired up my signal generator again and started on the Main RX with a 
signal on the following frequencies and with these results:

Filter settings: 2.7KHz
Preamp off
Att: no
Signal strength: -63 dBm
Mode: USB

28.130 = S6
21.130 = S6
18.130 = S4
14.130 = S2 (!!)
10.130 = S4
7.130 =  S8 (!!)
3.513 =  S6

Same settings at the Sub RX (via AUX IN):

28.130 = S9+5
21.130 = S9+10
18.130 = S9+10
14.130 = S9+10
10.130 = S9+5
7.130 =  S9+10
3.513 =  S9+10

You will see that there are dramatic differences at the Main RX from 
band to band and from S2 (14 MHz) up to S8 (7 MHz). And of course when 
comparing Main RX with Sub RX. Also tried different filter settings (AM, 
CW), no change.

I have no idea what is happening here and what to do next.

73 Udo, DK5YA


Am 25.04.2016 um 22:02 schrieb Udo Langenohl - DK5YA:
> Gentleman,
>
> thanks for all so many replies. Will try to check all ideas tomorrow,
> XYL permitting ... ;-).
>
> 73 Udo, DK5YA
>
> P.S.: The issue occurs at the RX IN and TVTR IN ports of the KXV3A too.
>
> Am 25.04.2016 um 17:57 schrieb Jerry:
>> Reseat the internal coax jumpers in the surf signal path.
>>
>> Sent from my iPad
>>
>>> On Apr 25, 2016, at 11:52 AM, Graham g3tct <g3tct at g3tct.co.uk> wrote:
>>>
>>> Hi Udo
>>> Before you start tearing the rig apart, two ideas:-
>>>
>>> -is there a big difference for weak signals of say S4?
>>> -if not, it may just be the S meter calibration that needs attention.
>>> -if so, preamp on for either? Att on for main?
>>>
>>> HTH
>>> Graham
>>>
>>>> On 19:59, Udo Langenohl - DK5YA wrote:
>>>> Gentleman,
>>>>
>>>> I'm struggling with a Main RX vs. Sub RX issue. My Main RX is rather
>>>> deaf compared to the Sub RX. I see at least 23.5dB attenuation
>>>> between Main RX and Sub RX when comparing highly stable signals from
>>>> my signal generator (HP8664A). This is only for ANT1/2 vs. AUX-IN!
>>>> Example:
>>>> -33dBm on 28.500
>>>> into AUX-IN (SUB RX): exactly 59 +40dB
>>>> into ANT 1 (Main RX): 59 +15dB
>>>> into ANT 2 (Main RX): 59 +15dB
>>>>
>>>> I've checked all the usual suspects (pin diodes):
>>>> D1 and D5 on the KXV3A: o.k.
>>>> Each and every pin diode on the SUB IN board: o.k.
>>>> D5 on the Main RX board: o.k.
>>>>
>>>> This is a K3 #59xx with almost everything inside money can buy.
>>>>
>>>> My second K3 (serial #39xx) does not show this strange behavior.
>>>> Main RX and SUB RX show exactly the same values on ANT1/2 and AUX
>>>> IN. -33dBm is 59+40 on MAIN and SUB RX, no matter if Ant1, 2 or AUX IN.
>>>>
>>>> Any idea? I'm searching for weeks now and I'm close to give up.
>>>>
>>>> Udo, DK5YA
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>>
>>
>

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