The auxiliary power board supplies the voltage to the sound board. I would replace the LM340T ( or 7805). this is the +5 volt reg. Also the op-amp MC3403 (or LM324AN or NTE987) can be blown. Double check all your connections!!!

Looks like the 7805 has a lower amperage. I get all my parts from digikey. Heres the link:

http://www.digikey.com/product-detail/en/LM340T-5.0%2FNOPB/LM340T-5.0-ND/6237

Here is the datasheets for both:

http://www.ti.com/product/LM78L05

http://www.futurlec.com/Linear/LM340T-5.shtml

If you click on the datasheets it will show you the different versions of this part. The link was to the part you are looking for, just add the quantity.