We can't proofread or correct entire sentences here, dewylotus, but there's nothing grammatically wrong with "broken down." (I'd be more likely to describe a car as "broken down" than a computer, but that's a matter of style or usage, not grammar.)
Thank you Florentia for your kind reply. Because I am an English teacher, I have to know exactly whether the sentence is right or wrong,idiomatic or not, so that I can guide students through their study. Thanks for your patient reply which is very helpful.