Hello Geraldo,
I have cleaned my Marantz 2235 a few weeks ago. I noticed on some forums and Deoxit reviews it was strongly mentioned by some that you need two Deoxit products. The normal Deoxit D5 (red can) and the green Deoxit F5 can (faderlube), which you use after as coating. Apparently if you don't use the Faderlube after, you need to repeat the cleaning every once in a while.
I bought the small size red can, which is enough. I cleaned every pot twice before closing and moved the slider and the knobs like 50 times per cleaning to make sure the dirt is removed. You will probably feel the knobs rotating more easy after.
I found the following video the most easy to see on where to clean:
I suggest you also read the following post on cleaning, it will give you an idea on what to do and what not to do:
https://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/
As mentioned by others, I have also new caps, but the cleaning with Deoxit is a very good start. For me it fixed some sound issues.