Belge tarayıcısını kullanırken mutlaka donanım bağlantısını kontrol etmelisin.

Kullanırken means while using.

It comes from:

• kullanmak = to use
• verb stem: kullan-
• -ırken / -ken = while doing

So:

• kullanırken = while using

This structure is very common in Turkish:

• yemek yerken = while eating
• konuşurken = while speaking
• çalışırken = while working

In this sentence, Belge tarayıcısını kullanırken... means While using the document scanner...

Because the noun is a specific object and it also includes a possessive relationship.

Break it down:

• tarayıcı = scanner
• belge tarayıcısı = document scanner
  Literally, document its-scanner, which is how Turkish often forms noun compounds.
• belge tarayıcısını = the document scanner (as the definite direct object)

So the endings are doing two jobs:

1. -sı
   marks the compound noun: belge tarayıcısı = document scanner

2. -nı
   adds the accusative/direct object ending because it is the thing being used

So:

• Belge tarayıcısı = a/the document scanner
• Belge tarayıcısını kullanmak = to use the document scanner

That -n- is a buffer consonant.

In Turkish, when a noun already has a 3rd-person possessive ending like -ı / -i / -u / -ü or -sı / -si / -su / -sü, and then you add another ending such as the accusative, Turkish often inserts -n- to connect them.

For example:

• tarayıcısı = its scanner / scanner of the document
• tarayıcısını = the scanner (as object)

And:

• bağlantısı = its connection / hardware connection
• bağlantısını = the connection (as object)

So the -n- is not part of the root; it is just there to make the word easier and grammatically correct.

Donanım bağlantısı means hardware connection.

It is another Turkish noun compound:

• donanım = hardware
• bağlantı = connection
• donanım bağlantısı = hardware connection

This is built in the same way as belge tarayıcısı:

• belge tarayıcısı = document scanner
• donanım bağlantısı = hardware connection

Then in the sentence it becomes:

• donanım bağlantısını kontrol etmelisin
• you should/must check the hardware connection

Because both are definite direct objects.

In Turkish, if the object is specific, it usually takes the accusative ending:

• tarayıcı kullanmak = to use a scanner
  (any scanner, non-specific)
• tarayıcıyı kullanmak = to use the scanner
  (a specific scanner)

In your sentence, both are specific:

• Belge tarayıcısını kullanırken = while using the document scanner
• donanım bağlantısını kontrol etmelisin = you should check the hardware connection

So the accusative shows that these are particular, identifiable things.

Mutlaka means something like:

• definitely
• certainly
• be sure to
• without fail

In this sentence, it adds emphasis:

• kontrol etmelisin = you should / must check
• mutlaka kontrol etmelisin = you definitely should / must check

So it makes the advice or instruction stronger.

Etmelisin means you should do or you must do, depending on context.

It comes from:

• etmek = to do
• stem: et-
• -meli / -malı = should / must
• -sin = you (singular)

So:

• etmeliyim = I should do
• etmelisin = you should do
• etmeli = he/she/it should do
• etmeliyiz = we should do

In this sentence:

• kontrol etmelisin = you should check / you must check

Because kontrol etmek is a common verb phrase meaning to check.

It can be either, depending on tone and context.

The suffix -malı / -meli often expresses:

• recommendation: should
• necessity: must / need to

In this sentence, because of mutlaka, it sounds stronger than a mild suggestion. So in English it could be:

• you should definitely check
• you must check

If this is an instruction manual or technical advice, must may sound natural. In everyday teaching language, should definitely also works well.

Turkish word order is often more flexible than English, but the default neutral order is usually:

subject + objects/other information + verb

Here the main verb is at the end:

• Belge tarayıcısını kullanırken mutlaka donanım bağlantısını kontrol etmelisin.

Literally, it is close to:

• While using the document scanner, definitely the hardware connection check-you-should.

More natural English:

• While using the document scanner, you should definitely check the hardware connection.

Turkish usually puts the main verb at the end, and time/condition phrases like kullanırken often come earlier in the sentence.

Yes. The subject you is implied by the verb ending -sin in etmelisin.

So Turkish does not need to say sen unless it wants emphasis.

• kontrol etmelisin = you should check
• sen kontrol etmelisin = you should check
  (with extra emphasis on you)

This is very common in Turkish. Person is often shown by the verb ending alone.

Because kontrol etmek is a very common Turkish compound verb made from a noun plus etmek.

• kontrol = control/check
• etmek = to do/make
• kontrol etmek = to check

Turkish uses many expressions like this:

• yardım etmek = to help
• fark etmek = to notice
• telefon etmek = to phone
• kontrol etmek = to check

So kontrol etmelisin literally looks like you should do check, but it simply means you should check.

Only partly. A very literal version would be:

• Belge tarayıcısını = the document scanner
• kullanırken = while using
• mutlaka = definitely / certainly
• donanım bağlantısını = the hardware connection
• kontrol etmelisin = you should/must check

So a near-literal English order would be:

While using the document scanner, you should definitely check the hardware connection.

That is already quite natural in English, but the Turkish grammar works differently underneath, especially with:

• noun compounds like belge tarayıcısı
• accusative marking
• the -ken structure
• the modal suffix -meli

Yes. This is a very productive pattern in Turkish.

You can attach -ken or its common form after a verb stem to mean while doing:

• okurken = while reading
• yazarken = while writing
• araba kullanırken = while driving
• beklerken = while waiting
• çalışırken = while working

So if you learn kullanırken, you can reuse the same pattern very widely.

It is mostly neutral and suitable for instructions, manuals, technical advice, or standard spoken/written Turkish.

A few things make it sound instructional:

• mutlaka adds strong emphasis
• -melisin gives advice/necessity
• vocabulary like donanım bağlantısı is technical

It is not especially casual, but it is not overly formal either. It sounds like a normal instruction such as something a teacher, technician, or manual might say.