David Farber wrote:

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** Good servicing practice requires that you FIRST observe a fault
before delving inside to find the cause.

Consider that the unit may have no fault at all, the reported noises
being fed in from an external device and / or are due to AC supply
transients.


.... Phil


I would agree with you up until the point where after several days of
waiting, and no faults are exhibited, then a peek inside the unit might give
you a clue. Maybe something spilled inside, or perhaps another tech might
have done some creative repairs.


** The flaw with that idea is that you will very often find something odd looking and wrongly assume it must be the cause of the reported fault - when it is not.

False alarm reports are VERY common with guitar amps and accessories plus also with disco equipment and PA gear.

If after a reasonable time running and testing a unit, it shows no sign of the reported fault then it becomes the owner's problem to DEMONSTRATE the fault to the repairer.





..... Phil