This is a studio monitor autoamplified speaker. It starts with apparently normal volume but after a minute or less it begins to drop volume.
Poor chinese materials and construction inside. But worst part is that the chinese that builds them applies a black glue to prevent vibration in capacitors and larger components. A very common subject in this forum, a budm's favorite: this glue becomes conductive and corrossive as it heats and becomes dry and brittle. Components that are underneath are corroded, specially their legs, eventually breaking.
Basically it's a cleaning job. Biggest problem was that R105 was very corroded, it fell apart when I removed glue and I couldn't read color bands. Reading was 5.7kΩ, a non standard value? I replaced with 5.6kΩ. Please, if someone opens one unit having this resistor in better shape, please confirm its value. Z101 is a 16V zener. I could save this one. Q101 is a 2SD667A, legs partially corroded. I mention this because they put glue over these components and they may become hard to identify if they need to be replaced. R100 and R101 are 2.2kΩ.
Poor chinese materials and construction inside. But worst part is that the chinese that builds them applies a black glue to prevent vibration in capacitors and larger components. A very common subject in this forum, a budm's favorite: this glue becomes conductive and corrossive as it heats and becomes dry and brittle. Components that are underneath are corroded, specially their legs, eventually breaking.
Basically it's a cleaning job. Biggest problem was that R105 was very corroded, it fell apart when I removed glue and I couldn't read color bands. Reading was 5.7kΩ, a non standard value? I replaced with 5.6kΩ. Please, if someone opens one unit having this resistor in better shape, please confirm its value. Z101 is a 16V zener. I could save this one. Q101 is a 2SD667A, legs partially corroded. I mention this because they put glue over these components and they may become hard to identify if they need to be replaced. R100 and R101 are 2.2kΩ.
