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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Ashdown MAG 300 amp, 2004
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. |
#2
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Ashdown MAG 300 amp, 2004
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? |
#3
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Ashdown MAG 300 amp, 2004
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 |
#4
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Ashdown MAG 300 amp, 2004
"N_Cook" wrote in message ... 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 |
#5
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Ashdown MAG 300 amp, 2004
"Arfa Daily" wrote in message ... "N_Cook" wrote in message ... 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. |
#6
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Ashdown MAG 300 amp, 2004
On 31/07/2013 09:31, Gareth Magennis wrote:
"Arfa Daily" wrote in message ... "N_Cook" wrote in message ... 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 |
#7
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Ashdown MAG 300 amp, 2004
I picked up the wrong bridge, the original Frontier one does have a
central hole |
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