[Elecraft] K3 Sub Receiver Problems

[KGØUS]

I am confident that I am operating the sub receiver properly.  I have also
compared the main receiver and sub assembly with the sub receiver
approximately 3 S units or 18 dBs down from the main receiver.  

Engaging the ATT attenuator on the sub receiver drives the signal, no matter
how strong, down to nothing on the S meter and inaudible in the speaker.  

Engaging or disengaging the PRE preamp on the sub receiver has no effect on
noise or signal level.

I think that the sub receiver has taken some damage from my recent SO2V and
diversity operations while running high power.

I recently located and downloaded the K3 schematics from the Elecraft web
site.  The sub receiver schematic is located on pages 53 and 54 of the
drawing package.

The upper left corner of the schematic on page 54 contains the 10 dB
attenuator consisting of R37 (100 Ohms), R43 (68 Ohms), and R45 (100 Ohms). 
I removed the KRX3 sub receiver PCB with my static pad and wrist strap. 
Using my DVM R43 and R37 are both “open” while R45 is practically “open”
measuring over 400 K Ohms.  This pretty much explains my problem with the
sub assembly attenuator circuit.

Any ideas as to what else I can check using my DVM while I have the PCB out
to troubleshoot the preamp problem along with the 18 dB down sensitivity
problem?  Will a standard diode check work on the PIN diodes D3 and D4 on
the input and output of the preamp circuit?

Thanks,
Dave KG0US




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