Ashdown MAG 300 amp, 2004

[N_Cook]

Both 6.3amp fuses blown, 2 diodes of the bridge rectifier s/c. Internal
failure of this bridge, dodgey looking splodge logo, presumably Fronter
logo and 8amp rating, marked
AC BP8-04
or something else to change as well?
Main caps look ok and ESR (for what its worth in such cases) ok
The 2 failed diodes are
-ve to AC
+ve to other AC
Suspiciously 2 solder points look like crazed PbF solder but all is SnPb,
melted and reformed? the 2 points are at the -ve terminal and the AC
terminal of the other failed diode. Output devices DVM-D cold test as
expected. No heated traces or even obvious gaseous eruptions from the
bridge or anything out of the normal. No reported preceeding noises
prior to failure.

 

[dave]

On 07/30/2013 07:00 AM, N_Cook wrote:

Both 6.3amp fuses blown, 2 diodes of the bridge rectifier s/c. Internal
failure of this bridge, dodgey looking splodge logo, presumably Fronter
logo and 8amp rating, marked
AC BP8-04
or something else to change as well?
Main caps look ok and ESR (for what its worth in such cases) ok
The 2 failed diodes are
-ve to AC
+ve to other AC
Suspiciously 2 solder points look like crazed PbF solder but all is SnPb,
melted and reformed? the 2 points are at the -ve terminal and the AC
terminal of the other failed diode. Output devices DVM-D cold test as
expected. No heated traces or even obvious gaseous eruptions from the
bridge or anything out of the normal. No reported preceeding noises
prior to failure.

DVM-D cold test? Amps can become radio transmitters and fry themselves
without any audible indication, other than maybe some "rizzing" on the
violins. Are the output devices shorted?

 

[N_Cook]

On 30/07/2013 15:12, dave wrote:

On 07/30/2013 07:00 AM, N_Cook wrote:
Both 6.3amp fuses blown, 2 diodes of the bridge rectifier s/c. Internal
failure of this bridge, dodgey looking splodge logo, presumably Fronter
logo and 8amp rating, marked
AC BP8-04
or something else to change as well?
Main caps look ok and ESR (for what its worth in such cases) ok
The 2 failed diodes are
-ve to AC
+ve to other AC
Suspiciously 2 solder points look like crazed PbF solder but all is SnPb,
melted and reformed? the 2 points are at the -ve terminal and the AC
terminal of the other failed diode. Output devices DVM-D cold test as
expected. No heated traces or even obvious gaseous eruptions from the
bridge or anything out of the normal. No reported preceeding noises
prior to failure.

DVM-D cold test? Amps can become radio transmitters and fry themselves
without any audible indication, other than maybe some "rizzing" on the
violins. Are the output devices shorted?

No , output devices, cold test , seem fine.
Looking at the Fronter datasheet, the bridge has to be derated to only 3
amps at 40 deg C, which seems surprisingly low temp. This amp was all
day sitting outdoors in the cloudless sun and failed after 1 hour of use
in a set. So 40 deg C was quite likely exceeded, so probably the reason
for failure.
As constricted in space , without going off board, I see a heatsink
being bolted to the replacement same rating bridge, or wiring off board
and bolting to the chassis

 

[Arfa Daily]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:kt8gif$ah6$1@dont-email.me...

Both 6.3amp fuses blown, 2 diodes of the bridge rectifier s/c. Internal
failure of this bridge, dodgey looking splodge logo, presumably Fronter
logo and 8amp rating, marked
AC BP8-04
or something else to change as well?
Main caps look ok and ESR (for what its worth in such cases) ok
The 2 failed diodes are
-ve to AC
+ve to other AC
Suspiciously 2 solder points look like crazed PbF solder but all is SnPb,
melted and reformed? the 2 points are at the -ve terminal and the AC
terminal of the other failed diode. Output devices DVM-D cold test as
expected. No heated traces or even obvious gaseous eruptions from the
bridge or anything out of the normal. No reported preceeding noises prior
to failure.

I've replaced a few bridges on various Trashdowns. Maybe just not very good
quality ones used by them ? Bad snubber caps across the bridge diodes ?
Maybe none at all ? Power surge at a 'village hall' gig maybe ? Bear in mind
that there's been a lot of lightning around the last few days ...

I've just had a mixer come in dead. It apparently failed during a storm when
there was a power surge due to the cellar at the venue where they were
playing, flooding ... :-\

Arfa

 

[Gareth Magennis]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:xjRJt.18598$cb5.8735@fx19.am4...

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:kt8gif$ah6$1@dont-email.me...
Both 6.3amp fuses blown, 2 diodes of the bridge rectifier s/c. Internal
failure of this bridge, dodgey looking splodge logo, presumably Fronter
logo and 8amp rating, marked
AC BP8-04
or something else to change as well?
Main caps look ok and ESR (for what its worth in such cases) ok
The 2 failed diodes are
-ve to AC
+ve to other AC
Suspiciously 2 solder points look like crazed PbF solder but all is SnPb,
melted and reformed? the 2 points are at the -ve terminal and the AC
terminal of the other failed diode. Output devices DVM-D cold test as
expected. No heated traces or even obvious gaseous eruptions from the
bridge or anything out of the normal. No reported preceeding noises prior
to failure.


I've replaced a few bridges on various Trashdowns. Maybe just not very
good quality ones used by them ? Bad snubber caps across the bridge diodes
? Maybe none at all ? Power surge at a 'village hall' gig maybe ? Bear in
mind that there's been a lot of lightning around the last few days ...

I've just had a mixer come in dead. It apparently failed during a storm
when there was a power surge due to the cellar at the venue where they
were playing, flooding ... :-\

Arfa

I have had 3 Ashdown Electric Blue 180 amps with failed mains transformers
so far. (Shorted primary)
The replacement toroid Ashdown supply is a lot bigger.


Gareth.

 

[N_Cook]

On 31/07/2013 09:31, Gareth Magennis wrote:

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:xjRJt.18598$cb5.8735@fx19.am4...


"N_Cook" <diverse@tcp.co.uk> wrote in message
news:kt8gif$ah6$1@dont-email.me...
Both 6.3amp fuses blown, 2 diodes of the bridge rectifier s/c. Internal
failure of this bridge, dodgey looking splodge logo, presumably Fronter
logo and 8amp rating, marked
AC BP8-04
or something else to change as well?
Main caps look ok and ESR (for what its worth in such cases) ok
The 2 failed diodes are
-ve to AC
+ve to other AC
Suspiciously 2 solder points look like crazed PbF solder but all is SnPb,
melted and reformed? the 2 points are at the -ve terminal and the AC
terminal of the other failed diode. Output devices DVM-D cold test as
expected. No heated traces or even obvious gaseous eruptions from the
bridge or anything out of the normal. No reported preceeding noises prior
to failure.


I've replaced a few bridges on various Trashdowns. Maybe just not very
good quality ones used by them ? Bad snubber caps across the bridge diodes
? Maybe none at all ? Power surge at a 'village hall' gig maybe ? Bear in
mind that there's been a lot of lightning around the last few days ...

I've just had a mixer come in dead. It apparently failed during a storm
when there was a power surge due to the cellar at the venue where they
were playing, flooding ... :-\

Arfa


I have had 3 Ashdown Electric Blue 180 amps with failed mains transformers
so far. (Shorted primary)
The replacement toroid Ashdown supply is a lot bigger.


Gareth.

I cannot see how an honest rated 8amp bridge could be in a 15mm square
pack. Replacement will be 4 amp 200V rating, with a hole to take a vaned
heatsink, no hole in the original (perhaps to get 8A it uses the central
area). The fan airflow in these amps is fine for the output heatsink but
the bridge is sheltered by the main caps and wiring knot, vane will be
off-centre poking into clear air, off the edge of the board

 

[N_Cook]

I picked up the wrong bridge, the original Frontier one does have a
central hole