2nd Xtal Filter and Product Detector Output problems

[K5JAZ]

I am using the procedures in a Rev C manual, Appendix E, Page 10-11 to
troubleshoot a "dead receiver" problem. All Rework Eliminators are
installed. Signal tracing through the PLL/VCO and Low-Pass Filter,
Bandpass Filter, and T-R Switch produced expected measurements. In the
Mixer, I.F. Amp, and Xtal Filter section, some anomalies were found.
Specifically, the 2nd Crystal Filter Output measured at U11 pin 1
expects 0.27Vrms but measures only 0.17Vrms (paragraph 9). The Product
Detector Saturated Output measurement expects 0.58Vrms but measures
only 0.08Vrms (paragraph 10). These measurements produced with input
of 0.15Vrms as measured at U12, pin 8 per instructions in paragraph 8.

I reheated solder joints on all components around these sections with
no change of measurements. Any help appreciated.


Regards,
Jim Brown, K5JAZ
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[Don Wilhelm-4]

Jim,

If you had the expected output at U12 pin 8, but less than expected at
U11 pin 1, then there is a problem between those two points.  Look at
the schematic in conjunction with these troubleshooting steps to find
what lies between the two points - in this case, look in the lower right
quadrant of RF Board schematic sheet 2.

Since the signal is going through a crystal filter, move the frequency a
little bit to see if the level increases.

Concentrate on the 2nd IF filter before proceeding to the Product Detector.

73,
Don W3FPR

Jim Brown wrote:

> I am using the procedures in a Rev C manual, Appendix E, Page 10-11 to
> troubleshoot a "dead receiver" problem. All Rework Eliminators are
> installed. Signal tracing through the PLL/VCO and Low-Pass Filter,
> Bandpass Filter, and T-R Switch produced expected measurements. In the
> Mixer, I.F. Amp, and Xtal Filter section, some anomalies were found.
> Specifically, the 2nd Crystal Filter Output measured at U11 pin 1
> expects 0.27Vrms but measures only 0.17Vrms (paragraph 9). The Product
> Detector Saturated Output measurement expects 0.58Vrms but measures
> only 0.08Vrms (paragraph 10). These measurements produced with input
> of 0.15Vrms as measured at U12, pin 8 per instructions in paragraph 8.
>
> I reheated solder joints on all components around these sections with
> no change of measurements. Any help appreciated.
>
>
> Regards,
> Jim Brown, K5JAZ
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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