One astrologer at Kakinada told us that Lord Venkateswara is actually the Goddess Bala Tripurasundari, with long hair at the back. Hence the name Balaji!
Here's the experience of Swami Brahmananda at Tirumala: (God Lived With Them, page 106, bottom)
In Tirupati Maharaj [Swami Brahmananda] saw the Divine Mother in the image of Lord Venkateswara. His body shivered in ecstasy. Later he said to Sharvananda: "I have distinctly seen the form of the Divine Mother. Please inquire about it." After inquiry and close examination of the image and sanctuary, it was found to have been originally a Shakti temple, later converted into a Vishnu temple, probably under the influence of Ramanuja.
Another claim is found here.
The idol in Tirupati temple :
Legend has it that Ramanujacharya took over the temple from jains and driven away jains from south India. To win over the Jains, he presented the deity with golen sankh and chakra, which were not there originally (for which he added a story that these were given away by lord Balaji to warring Tondaman Chakravarthy).
However, it is not the Jain Thirthankara's idol but Devi Bala Tripura Sundari's. Earlier to jains, it was worshipped as Kumara Swamy for ages. prior to that may be many others too might have worshipped it considering it as their dieties.
In support of claiming it as Devi's idol, there are many evidences. Few among being:
the deity has lot of long hair, like for Stree Murthy.
the sculpture norms has it that for stree (woman) sculpture, the upper portion is longer than the legs portion and the idol has short legs.
The Anandanilaya sikhara has lions, which is evident that it is Bala Tripura Sundari.
that's how the name Balaji derived.
Is the temple at Tirumala really the abode of the Goddess Bala Tripurasundari?
What do scriptures say?