Technically not always, in "An Unearthly Child" we are introduced to the TARDIS and it appears it is the first time the chameleon circuit has failed. The Doctor says:
It's still a police box. Why hasn't it changed? Dear, dear, how very disturbing.
This establishes that the TARDIS is now stuck as a police box, but <PERSON> reveals that it wasn't always a police box:
<PERSON>: It should have changed. Wonder why it hasn't happened this time.
<PERSON>: The ship, you mean?
<PERSON>: Yes, it's been an Ionic column and a sedan chair.
<PERSON>: Disguising itself wherever it goes.
<PERSON>: Yes, that's right. But it hasn't happened this time. I wonder why not.
In the "Attack of the Cybermen" serial, the TARDIS changes several times after the Doctor attempts to fix the chameleon circuit. 837
First into an ornamental dresser, as outlined in the script below:
DOCTOR: This looks familiar.
<PERSON>: Where are we?
DOCTOR: Scrap yard.
<PERSON>: I didn't mean that. I meant, whereabouts on Earth are we?
DOCTOR: London.
PERI: It didn't change.
DOCTOR: Hmm?
PERI: I thought you said it was going to blend into its surroundings.
DOCTOR: Oh, she's probably thinking about it. Come on, let's find out where those signals are coming from.
(The Tardis changes into a highly ornamented dresser.)
PERI: Oh, neat, Doctor.
DOCTOR: Neat?
PERI: Very neat. I mean, there's nothing at all incongruous about that.
DOCTOR: Well, she hasn't done it for a long time. She's out of practice.
PERI: Of course, Doctor.
Here is the TARDIS shown in mid-transformation and as the final dresser.
Later it transforms into a pipe organ (as pictured) and the Doctor plays it briefly.
(The Tardis materialises in <PERSON>'s junk yard as a small pedal pipe organ.)
DOCTOR: This is getting ridiculous.
PERI: I'm not saying a word.
DOCTOR: I was certain I'd fixed it.
(He pulls out a stop and plays the opening line from <PERSON> Toccata and Fugue in B Minor.)
And lastly it turns into a gate.
(A pair of large wrought iron gates, the sort you'd find at the entrance to the driveway of a very large house, materialise in a corridor. The Cybermen lead their captives out.)
<PERSON>: What happened to the organ?
<PERSON>: Do you really want to know? Oh, this place is so cold!
The TARDIS is also shown undisguised in "The Name of the Doctor" silver-grey cylinder.
This varies slightly from the undisguised TARDISes shown in "The War Games" serial. 837