cien - 2:17 am on Feb 9, 2011 (gmt 0)
Ouch! Easier would be to set an alternate ad to the charity of your choice in your adsense account for each channel than doing all that editing work. All your channels will use your new alternate ads.
You don't have to change ad codes. Adsense will only stop showing PSA ads. The other commercial ads will keep showing fine with your existing code. If you set your alternate ad in your channels, when there is no commercial ad available to show, it will show your charity or whatever you set in your channel.