Archived from groups: rec.audio.pro (
More info?)
Scott Dorsey wrote:
> Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
> >
> >> If the output MOSFETs are blown, then the drivers may well also be blown.
> >> So might the gate resistors.
> >
> >I'll beg to differ. That would be a rare condition IMHO.
> >
> >Hitachi (including other manufactuer similar style ) mosfets usually fail
> >open-circuit without destructive behaviour.
>
> Right, but often blown output devices are a symptom of something else gone
> wrong farther up the chain, rather than the original problem. Gate resistors
> gone open will take the output stage out with oscillation sometimes, for
> example.
My own experience has been mainly with failed devices due to overtemperature ( on
C Audio amplifiers that have marginal cooling for example ).
C Audio used to consider the failed devices as *normal* !
They also had poor lifetime on the PSU electrolytics as they stood in the path of
the searing heat from the fan cooling !
Replacement of either / both was considered normal service / repair !
Harman bought C Audio a number of years ago in a classic Harman move that left
the staff that knew the product in Cambridge UK unemployed whilst moving the
inventory to the Soundcraft site some 40 miles south approx.
A friend of mine who worked for Harman UK said at the time that they had a pile
of bits that they had no idea what to do with !
C Audio had just introduced the rather poor GB bipolar series. This eventually
ended up rebadged as the Crown CE series ! Nuff said ?
Does Harman have a death wish ?
Graham