A very significant exception must be brought up in the accentual pattern of phrasal verbs when they are separable. The rule is that, in neutral tonicity, when the particle is separated from the verb and there is a lexical object in between, the object bears the accent.
(128) You let your brother down.
Of course this does not apply when the object is a pronoun.
Owing to the frequency of its occurrence, this displacement of the accent in phrasal verbs constitutes a pretty important case. However, in spite of being amply reported in some of the more specialized literature (Wells, Ortiz-Lira, Hewings, among others), it generally goes unmentioned in the majority of EFL materials. The consequence is that English students usually learn just one fact about the accentuation of phrasal verbs –stress on the particle, whatever the case-, which is only half the truth.
Here are some examples of the accentuation of the object in separable phrasal verbs.
(130) For twenty years I tried not to and then I guess one day I let my guard down (John Mahoney; Blackpool, Lancashire, UK).
(131) You gotta go down to that station and talk to the boss and get him his job back (John Mahoney; Blackpool, Lancashire, UK).
(132) when Proby had his appendix out (Hugh Laurie; Oxford, England).
(133) I want my money back (Stephen Fry; London, UK)
Interestingly, the same pattern applies to certain idiomatic constructions which, without being proper phrasal verbs, are similarly built.
(134) She longed to run away from this dreadful bore and cry her eyes out (Tadhg Hynes -Dublin, Ireland- reading a story by Thomas Hardy).
(135) So maybe he was too busy working his tail off (Kelsey Grammer; Virgin Islands, US).