Tube and Tube Socket Cleaning

what kind of noise is that? microphonic? ac? hissing?
i just realy wonder how the other socket isn't noisy being basically as "dirty".

the cleaning doesn't help everytime as in this funny story:

a blondie is trying to start up her malfunctioned mercedes without any success. another blondie in jaguar drives by stops and trying to help:
--did you wipe your dashboard?
--yes
--did you wipe your head and tail lights?
--yes i did!
--did you clean your rims?
--certainly!
--and still you can't start it?
--no
--sorry, can't help you than!

as to cleaning tube prongs and sockets it's considered to be a basic hyegine that you should excersise once in approximately every 300 hours. i use kontak with supplied wire-shaped brushes that can penatrate even sockets for small signal tubes all arround the sockets and prongs. if the oxiding is visible it's probably fine to use the fingernale file while i use de-oxiding spray and still try to remove it the "gentle way".

most-likely caps become to be statically noisy and need to be replaced especially ones in ground isolation circuitry.
measuring capacitors for the face value +-tolerance isn't an easy task and require havin an osciloscope to measure the discharge time so without any checking and suffering setting up an oscilloscope for the right scale just change them all by face value and with better quality.
checking low-wattage bias resistors is much easier task for the rated value.
fuses within such period of time even if functional can create an extra noise.
whenever you change the caps you should run your preamp(approx 1 hr) on no-signal operation meaning that you will have an input connected with muted or unpowered source.