Signs that a CD laser is dirty?

[JHZR2]

Hi,

What is the sign that the laser on a cd player is getting dirty? In my 83 300D, I have a JVC 12-disc RF changer going to the stock unit and speakers, and lately it tends to be really scratchy when I first start using it, but after 20-30 mins of being on, the scratchiness goes away. It is an RF unit, but I keep the entenna in a down position, and have tried changing the frequency (I have 10 options), but it is scratchy on all of them. This never used to be the case, and with a strong FM signal, the sound is very good (so I dont think it is the speakers, their quality seems to be fine)

Is this a sign that the laser could be dirty/bad or is it more likely a problem with the connections or radio itself?

Thanks,

JMH