Ok :)
this is a small video piece without audio (vhs tape noise i think)
starting with dolby adctivated, and after without dolby

Thanks for the sample.

It's hard to judge if the noise level is normal without a reference signal to compare it to.

In a linear audio track there will always be much more noise than a good HiFi track, even with Dolby. This is not a fault in the linear audio.

Tim, if i can ask, what is the purpouse to move the head to right ? this conical thing seems created for this, but there are no instructions on service manual.

I think on a reference tape we adjust it so picture and sound are in "lip sync" and when the tracking control is in the middle position the tracking meter reads maximum. It might need some adjustment after adjusting A/C head height with the other large nut. Normally neither nut needs adjusting.

thank you very much Tim

another question.. can i use the "anti-serial" method to replace some 1uF 50V NOT polarized caps?
(2 polarized 1uF 50V in serial mode with the two + connected)
i have found 2 of them with ESR of about 4 ohms and one with 7.4 ohms (c20 on servo board)

i will receive some 1uF 63V not polarized next month , but i want to make some tests to reduce this audio noise...

Yes but in series the capacitor value is reduced, so in this case each needs to be 2uF.

thank you i will try