Bu belge tarayıcısı bozulunca, teknik servisi aradım.

Because Turkish usually forms this kind of noun phrase as an indefinite noun compound:

• belge = document
• tarayıcı = scanner

When one noun modifies another in this pattern, the second noun normally takes the 3rd-person possessive ending:

• belge tarayıcısı = document scanner

So this is the standard Turkish way to say a scanner whose function is scanning documents.

It is the compound ending -(s)ı / -(s)i / -(s)u / -(s)ü, depending on vowel harmony.

Here the breakdown is:

• tarayıcı = scanner
• -sı = the compound/3rd-person possessive ending

So:

• tarayıcı + sı → tarayıcısı

The s appears as a buffer consonant because the word already ends in a vowel.

Bozulunca comes from:

• bozulmak = to break down, to become broken
• -ınca / -ince / -unca / -ünce = when, once, after

So bozulunca means something like:

• when it broke down
• once it broke down
• after it broke down

It introduces a time clause before the main action.

Because bozmak and bozulmak are different verbs:

• bozmak = to break something, spoil something
• bozulmak = to break down, become broken

In this sentence, the scanner itself is the thing that stopped working. Nobody is directly shown as breaking it. So Turkish uses the intransitive form:

• tarayıcı bozuldu = the scanner broke down

That is why the clause is bozulunca.

Usually it gives a time relationship, but in real sentences it can feel slightly different depending on context:

• when
• once
• after
• sometimes even a light because/since feeling

In this sentence, the natural sense is:

• When/After the document scanner broke down, I called technical service.

The idea is mainly first this happened, then I did that.

Here -i marks the definite direct object.

• teknik servis = technical service / the repair service
• teknik servisi = the technical service, as a specific object of the verb

The verb aramak takes a direct object:

• birini aramak = to call someone
• servisi aramak = to call the service department

So teknik servisi aradım means I called the technical service.

In this sentence, it is best understood as the accusative ending marking a definite object.

• teknik servis = technical service
• teknik servisi aradım = I called the technical service

This can confuse learners because -i can also look like a possessive ending in other contexts. But here the phrase is functioning as the object of aradım, so the important point is that it is the definite object marker.

Because Turkish says to call someone/something with a direct object, not to call to someone.

So:

• annemi aradım = I called my mother
• teknik servisi aradım = I called technical service

English learners sometimes expect a preposition, but Turkish does not use one here.

It breaks down like this:

• ara- = call, search
• -dı = past tense
• -m = I

So:

• aradım = I called

Because of consonant changes and normal spelling, it appears as one word.

Turkish often puts the background or time clause first, and the main action later:

• Bu belge tarayıcısı bozulunca, teknik servisi aradım.

Literally, the structure is:

• When this document scanner broke down, I called technical service.

This is very natural Turkish word order. You could also rearrange it, but this version is clear and common.

Bu means this.

So:

• bu belge tarayıcısı = this document scanner

It points to a specific scanner, probably one that is physically present or already known from context.

Yes. For example:

• Bu belge tarayıcısı bozulduğunda, teknik servisi aradım.

This also means when the document scanner broke down, I called technical service.

The difference is mostly one of style and nuance:

• bozulunca often feels a bit more natural and event-based: when/once it broke down
• bozulduğunda can sound a bit more neutral or formal: when it was broken / when it broke down

In everyday Turkish, bozulunca is very common here.