[quote name='0175westwood29' timestamp='1357117481' post='1917564']
I think my tu3 can supply up to 7 boss pedals? [/quote]
It depends on the ma rating of those 7 pedals.
Generally speaking, you can treat milliamps like amp wattage headroom, you want more than you need. I would want my power supply to not be running over half capacity, so say the Boss tuner can supply 200ma, and you have 7 pedals that total 170ma, you're going to probably start hearing some excess noise and perhaps some sag with regards to the actual effects.
In your case, if you have 7 Boss pedals that add up to 90ma (Check Boss Area for the ratings), you're fine.
Cheers
Si