The sanctum of Thirupathi Venakateswara, Balaji contains the Idol of Lord Venkateswara and two more Idols of Srinivasa.
Such is the imposing and divine presence of Lord Balaji with His stunning looks, we often miss what else is present in His Sanctum!

There are three idols of Lord Balaji, Srinivasa.
They are,

1.Sri Bhoga Srinivasa,
2) Ugra Srinivasa,
Legend has it that fire broke out in the village destroying houses during Brahmotsavam at Tirumala in the 14th century A.D. When prayers were offered to the God, a@ vision appeared to a devotee with a message from Lord Srinivasa himself. With the change in times, the Ugra Srinivasa idol could no longer remain the processibon idol and a new idol would be found as utsava murti (Malayappa swami). The Ugra Srinivasa idol is no longer brought out of the temple after sunrise and it is believed that sunrays touching the idol would spark fire in the temple complex.
3) Koluvu Srinivasa,
4) Sri Malayappa,
5) Sri Krishna,
6)Srirama, Sita, Lakshmana and Sugreeva and
7) Sri Chakrattalvar. ‘
It is rare to find seven idols in a Garbha Gruha.
Three of Srinivasa are found.
Srinivasa is an Avatar of Vishnu.
Vishnu,though according to functions is Kshatria,because He protects like a father,the term Vishnu is from Jishnu,meaning one who supports,The Vishnu Purana is classified as Sattvic , not Rajasic as protection is the function of a King with Compassion,Kshama,the ability to forgive.
Yet in Thirupati we find Bhoga Srinivasa given the first place.
Bhoga means enjoyment.
In Srinivasa avatar ,His specific purpose has been to shower Kshama and Blessings and He enjoys it.
Hence Bhoga Srinivasa gets the priority.
Ugra,Srinivasa represents His aspect of unforgiving anger.
Many are not aware of this aspect of Lod Balaji,Srinivasa.
As much as He is known for His munificence,He does not forgive a forget a slight nor goes any of the dues to Him by the Devotees,uncollected.
If one has dues to Him ,like a vow taken to visit Thirupati or forgets to offer money if one has taken a vow to do so.
Normally the signal he is not pleased with you in fulfilling your vow to Him, is your getting inexplicable stomach ailments.
The solution is to fulfill your vow.
Then, as a Father He would ignore your omission and shower you with His Grace.
This,I have experienced personally and also from others.
These do not have any scientific or even religious explanation.
Period.
As to me ,if my issue is resolved it is more than enough, I do not waste my time how and why the problem is solved.
Not very rational,
Isn’t it?
That is way the things are.
‘Koluvu Srnivasa is Utsava Murthy.
I am researching into the presence of Rama,Sita,Sugreeva and Chakkarathalvar in the Sanctum.
They,in my opinion, have a historical connection.
Shall write.
‘
Sri Bhoga Srinivasa Idol is a true copy of the Dhruva Bera(Main Deity) except that the Sanku and Chakra are permanently fixed in the case of Bhoga Srinivasa. Sri Bhoga Srinivasa gets Abhishekam every morning unlike the Dhruva Bera to which Abhishekam is performed only on Fridays.
Every day after the morning Thomala Seva, a darbar called Koluvu is held in the Tirumamani Mantapam where the deity is brought and is seated in a silver chair with a gold umbrella above him. This idol officiates for the main idol during this function and hence his name is Koluvu Srinivasa.
He is akin to the guardian deity and supervises the temple household, and keeps himself posted with all the affairs and revenue of the temple. The Panchangam or the Calendar of the day is also read out before Koluvu Srinivasa Every Day.
Description of Thirupathi Balaji’S Grabha Gruha is from the following link and quoted portions are from this source.
http://www.allgodscollections.com/2013/02/idols-in-garbha-griha-of-tirumala.html