Quando a tela ficar preta, vou ligar para a técnica imediatamente.

Because ficar often means to become or to end up in a state.

So:

• a tela está preta = the screen is black
• a tela ficar preta = the screen becomes/goes black

In this sentence, the idea is not just the screen’s condition, but the change into that condition.

This is because after quando referring to a future event, Portuguese uses the future subjunctive.

So:

• Quando a tela fica preta... = usually sounds like a habitual/repeated fact, something like Whenever the screen goes black...
• Quando a tela ficar preta... = When the screen goes black... in the future

This is a very common pattern in Portuguese:

• Quando eu chegar, te aviso.
• Se ele puder, ele vem.
• Assim que terminar, eu saio.

English does not have this exact form, so it often feels unusual at first.

For many verbs, the future subjunctive looks identical to the personal infinitive or to other familiar forms, so it can be hard to notice.

Here, ficar is the future subjunctive form for ele/ela/você.

In the clause:

• Quando a tela ficar preta

the subject is a tela, which is treated like ela, so ficar is the correct form.

A useful clue is the structure:

• quando + future idea → often uses the future subjunctive

Because adjectives in Portuguese usually agree with the noun they describe.

• tela is feminine
• so the adjective must also be feminine

That gives:

• a tela preta

If the noun were masculine, you would use preto:

• o monitor preto

So preta agrees with tela.

Vou ligar is the near future / periphrastic future and is extremely common in Brazilian Portuguese.

• vou ligar = I’m going to call
• ligarei = I will call

Both can refer to the future, but in everyday Brazilian Portuguese, vou ligar often sounds more natural and conversational.

So this sentence could also be:

• Quando a tela ficar preta, ligarei para a técnica imediatamente.

That is correct, but a bit more formal or less conversational.

Here it means to call.

Ligar can mean different things depending on context:

• ligar para alguém = to call someone
• ligar o computador = to turn on the computer

Because the sentence has para a técnica, the meaning is clearly to call the technician.

When ligar means to call someone in Brazilian Portuguese, it is commonly used with para:

• ligar para alguém = to call someone

So:

• vou ligar para a técnica = I’m going to call the technician

In everyday spoken Brazilian Portuguese, you may also hear:

• vou ligar pra técnica

where pra is the informal contraction of para a.

Here, a técnica means the female technician.

This can be confusing because técnico / técnica can be:

1. a noun

   • o técnico = the male technician
   • a técnica = the female technician

2. an adjective

   • uma explicação técnica = a technical explanation

In this sentence, it is clearly a noun, because it refers to a person.

Portuguese uses definite articles (o, a, os, as) more often than English does.

So where English might say:

• when screen goes black
• call technician

Portuguese more naturally says:

• quando a tela ficar preta
• ligar para a técnica

Using the article here sounds normal and natural in Portuguese.

Imediatamente is an adverb meaning immediately.

It modifies vou ligar, telling you when the speaker will call:

• vou ligar imediatamente = I’m going to call immediately

Its position is flexible. These all work:

• vou ligar para a técnica imediatamente
• imediatamente, vou ligar para a técnica
• vou imediatamente ligar para a técnica (less common in everyday speech)

The version in the sentence sounds very natural.

The comma separates the introductory quando-clause from the main clause.

• Quando a tela ficar preta, = subordinate clause
• vou ligar para a técnica imediatamente. = main clause

This is standard punctuation in Portuguese and also very natural in English:

• When the screen goes black, I’m going to call the technician immediately.

Yes, but the meaning shifts a little.

• Quando a tela ficar preta = When the screen goes black / becomes black
• Quando a tela estiver preta = When the screen is black

The first emphasizes the change of state. The second emphasizes the state itself.

In many real situations, both could work, but ficar preta is better if you mean the moment the problem happens.

Yes, preta is the normal and natural choice for a screen.

For objects and colors, preto/preta is usually the everyday word:

• tela preta
• carro preto
• camisa preta

Negro/negra exists, but it is less commonly used for ordinary color descriptions like this and can have other social or stylistic meanings depending on context. For a screen, preta is the expected word.

With ficar in the future subjunctive, the most direct reading is a future condition: when the screen goes black.

However, depending on context, Portuguese can sometimes use this structure in instructions or procedures in a way that feels close to whenever:

• Quando a tela ficar preta, reinicie o aparelho.

That can sound like an instruction for any time the problem happens.

So grammar-wise it is a future clause, but context can make it feel like a repeatable condition.

Yes.

• vou ligar para a técnica
• vou telefonar para a técnica

Both are correct and mean I’m going to call the technician.

In Brazilian Portuguese, ligar is more common in everyday speech. Telefonar is perfectly normal but may sound a little more formal or less conversational depending on the situation.