Re: 2nd Xtal Filter and Product Detector Output problems

Posted by Don Wilhelm-4 on May 08, 2009; 12:05pm
URL: http://elecraft.85.s1.nabble.com/2nd-Xtal-Filter-and-Product-Detector-Output-problems-tp2843492p2844917.html

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
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