Re: KNQ10 help needed

Adam Rong
 

Hi Jon,
 
If you have access to signal generator, you can try to inject a signal to the output of DBM and see if the diode switches and BPF are ok. For some reason, sometimes the circuit diagram is different from the PCB, but it should be easy to understand the theory of operation. For your issue, I would suggest you check band switch signal, 12VT signals on both ends of BPF, and check if the 1:1 transformer is ok. Once you confirm they are ok, you can check the PA board, or you can confirm PA board by injecting signal to the input.
 
73 de BD6CR/4, Adam


 

On Thu, Sep 8, 2011 at 3:42 PM, iapizloj <jon.iza@...> wrote:
 

Folks,
As I have a problem with the TX not producing any output, I have dedicated several hours now to figure out what is what and where it is on the PCBs using the schematics. I have been looking for KN/Q10A schematics, just in case they are a bit better than the ones on the Files section for the KN-Q10, but no cigar.
I am able to produce DSB on the 4.43 mixer, get SSB on the other side of the filter and plenty of mixing products after the DBM. When I get to the passband filters, I have 12VR and 12VT BUT the schematics on the side of the transformer going to the PA does not fit with what I have on my PCB. It looks like the isolating cap is connecting one leg to ground, and both legs of the transformer are at 0.7 V when 12VT is applied. Is that right?
Even though I have peaked all passband filters using a RF generator on RX, I cannot get even a pip while transmitting.
Any hint?
jon, ea2sn


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