FBT Maxx 2a, powered speaker, 2002

[N_Cook]

Small lighting unit and this powered speaker shared cheap and nasty plastic
multiway mains adaptor. Much crackles and bangs from bad contacts in the
adaptor but both survived working order . This amp had smoke coming from it,
at the time of the crackling. The bridge rectified 52-0-52V ac supply used
to have a cap across it, burnt up to just 2 pins now.
Only FBT schema, out there found, is for the MAX 9SA for which that
component is 100nF 200V , so replace with disc ceramic of that rating or
higher? or C +R ? and of course advice to obtain metal cased mains multiple
adaptor.

 

[N_Cook]

The owner may have interpretted as bad multiway mains connector.

This capacitor was .2 inch spacing, same as the one over the bridge for the
tweeter amp supplies. That shows no heating at all. That one is mustard
yellow 6x2.4x4.2mm high, marked
K2R
104K
That one must be 100 V rating at least, so probably MLCC for that size,
certainly if 200 V rating. The burnt one , same footprint may have been
taller or 100V rating only. Probably started with metal migration and MLCC
failure , yet again , starting with going ohmic down internal
micro-fractures then conflagration eventually, rather than bad adapter
leading to multiple mains spikes

 

[N_Cook]

N_Cook <diverse@tcp.co.uk> wrote in message
news:js16tv$55o$1@dont-email.me...

The owner may have interpretted as bad multiway mains connector.

This capacitor was .2 inch spacing, same as the one over the bridge for
the
tweeter amp supplies. That shows no heating at all. That one is mustard
yellow 6x2.4x4.2mm high, marked
K2R
104K
That one must be 100 V rating at least, so probably MLCC for that size,
certainly if 200 V rating. The burnt one , same footprint may have been
taller or 100V rating only. Probably started with metal migration and MLCC
failure , yet again , starting with going ohmic down internal
micro-fractures then conflagration eventually, rather than bad adapter
leading to multiple mains spikes

Will probably replace with 4 as 2x2 100nF/100V traditional disc ceramic for
4x power rating and one in place of the K2R one

 

[N_Cook]

I had to change the gain pot
The gain pot on these is reverse log , probably more like reverse log-log,
for the 5K pot the half-way split was .28K/5.1K , so a log pot slightly
adapted and 2 ends cut and cross-linked wiring