Ipod dock not working on panasonic sa-pt860,just keeps flashing "loading" have tested with another ipod as well.

Panasonic SC PT860 Manuals
The above link is the owner's manual - it may help.
Here are some other ideas:
Try to find out if the crackling sound is coming from all speakers or just one - you may just have one bad speaker.
If the crackling happens at high volume settings, you may be overdriving the system - you'll just have to turn it down!
Try turning down the bass or the subwoofer level.
Is the crackling present with all sources (TV, cable, DVD, bluetooth)?

Most BluRay players will work with home theaters. HDMI cables can be adapted to VGI inputs if necessary.

Look like malfunction AMP PCB Board.Please open top cover, unplug flex cable attached to connector AMP PCB. Try now power- ON the unit.

Try giving a disk clean up or change the lense

Not all ipod classic work with your SC-HC57 you need an older Panasonic SC-HC30 to work with that ipod :( or an iphone or ipod touch to work with your SC-HC57

http://elektrotanya.com/panasonic_sa-pt860.pdf/download.html

Should get you to a site where you can download the Manual.
Good luck. Hope this helps!

try this site http://elektrotanya.com/panasonic_sa-pt860.pdf/download.html

good luck!!

my dvd player is locked, how do I unlokc it

try to look for the settings that the source will be in ipod dock, if there is.

get it serviced as it happens due to the old band or ring kinda thing in the tray which aids in opening of it.