Collins 75S3 Receiver Noisy Rejection tuning and other questions

[W4AMV]

Good day and Happy Holiday,

I have a Collins 75S3 receiver which has a mild but annoying rejection tuning control. I suspect after many years that dust and material may be built up between the plates of C132, the rejection tune cap. Any commnets on other possibilities or method of service for this problem ?

Second item, is there a method of tracking the serial number of the S3 against date of manufacture ?

And finally... The 200 Hz CW filter... Operate mostly CW and as an example on 40 meters while tuning the 75S3, I would tend to use the wider mechanical filter in the LSB mode for CW. Then, ideal, switch to the CW mode (200Hz Filter) and do NO retuning of the main VFO or for that matter the BFO. That does not seem to be the case with the receiver and I find myself having to jockey the tuning of both. Is that typical or am I doing something wrong ? In my homebrew receiver which has a similar bandwidth crystal filter, I have it set so in the LSB mode, the BFO injection frequency, which is varactor tuned,  is properly retuned automatically with the switch from wideband to narrow filter.

Thanks for your comments !

Alan

[WB6NVH]

Regarding C132, put some DeOxit on the wiper area?

[WQ9E]

Alan,

For CW tuning select USB for wide bandwidth and then switch to CW when you need the narrow filter.  The beat remains the same when operated this way.

[W4AMV]

Thank you Rodger. Became obvious after I discoverd the BFO has an off mode !

On the rejection control, I am going to have to see how striaghtforward it is to remove the shield from the rejection control circuit which forms the Q multiplier. I don't want to make a bigger problem.

Alan