{Collins} 75S3C Ramblings

Hi All,

The band switch in my 75S3C has been acting up (i.e., dirty contacts) so I pulled the reciever out of the case and cleaned all the contacts with Deoxit D5. I spray a little into a small bottle and then use small electronic cleaning tips to rub on all the rotating surfaces while turning the switch shaft.  I go over each surface until the tip wipe remains clean.

While I was in there, I decided to install the electrolytic cap kit I purchased a few years back.  I pulled out C60 and check leakage and found it to leak quite a bit (although I did not notice any performance issues prior to removing it).  So I pulled out C29, C56, and C107 and replaced them with the new caps.  I then checked these 3 originals for leakage and found absolutely no leakage at all.  So, I did not replace the replacement triple can cap and will just hold the spare in reserve in case it is needed in the future.

I had not done an alignment since I purchased the receiver (probably 10-15 years ago) so I decided to go through it.  I made up swamping networks for aligning the 455 kc IF and found this 1st IF to be in perfect alignment.  I went through all the remaining sections and did not find any other out of spec either.  So, at least I put that to bed.

I then installed the S-meter linearity board designed by Don Jackson, W5QN (see The Signal, Issue 65, First Qtr 2012 and or QST, July 2014).  Wow, what a difference in S-meter performance.  S-unit/input power is very linear and the lower end of the scale is much more sensitive to weak signals. I am very happy with the results....great job Don.

So much for my ramble.

Happy Trails

de Mike

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