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Behringer GMX1200H guitar amp, 2011 (?)
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N_Cook
Jul 21, 2016, 7:09:59 AM7/21/16
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Stock fault ?
Phones o/p but no sp o/p. Both pcb traces to the main bridge rects fried.
2xLM3886 seem ok cold DVM "test".
Both main caps good ESR and capacity, diodes test ok.
Both main caps bowed ends and one with brownish dried "wax" at the
cross, presumably electrolyte but no hole seen.
All the caps on the PA are Xunda, don't remember seeing that name
before, suspect? presumably China.
Main caps are radial Xunda RK series, 3300uF,50V 105 deg C, the supposed
glue to the pcb has (heat?)failed and they can flop around on axial-type
gauge of terminals, not snap-in.
Phones o/p but no sp o/p. Both pcb traces to the main bridge rects fried.
2xLM3886 seem ok cold DVM "test".
Both main caps good ESR and capacity, diodes test ok.
Both main caps bowed ends and one with brownish dried "wax" at the
cross, presumably electrolyte but no hole seen.
All the caps on the PA are Xunda, don't remember seeing that name
before, suspect? presumably China.
Main caps are radial Xunda RK series, 3300uF,50V 105 deg C, the supposed
glue to the pcb has (heat?)failed and they can flop around on axial-type
gauge of terminals, not snap-in.
stevehen...@gmail.com
Jul 28, 2016, 3:22:53 PM7/28/16
to
Sounds like the main caps have blown/shorted
N_Cook
Jul 29, 2016, 7:12:48 AM7/29/16
to
Yes, in my opinion too small caps squashed into a small place on a
heated part of the board, considering the amount of space available in
this valve amp size, full width head .
18mm diam, x35mm, 105 deg C, is suspiciously small for 3300uF,50V.
Fixed 2 proper size 80V 3300uF to the cooler metalwork and so far
running fine.
Wire replacements to the burnt traces, leaving unburnt and unlifted
parts of the traces as "fuses"
heated part of the board, considering the amount of space available in
this valve amp size, full width head .
18mm diam, x35mm, 105 deg C, is suspiciously small for 3300uF,50V.
Fixed 2 proper size 80V 3300uF to the cooler metalwork and so far
running fine.
Wire replacements to the burnt traces, leaving unburnt and unlifted
parts of the traces as "fuses"
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