Amplifier Repair

Countfox

Novice Member
I have an Aiwa stacking system, and I'm afraid that I may have overloaded the AIWA MX-D91MK stereo integrated Amplifier/graphic equaliser by adding 2 small speakers (presumably wrong impedance) to the surround sound. When I turn the amp on, it activates; whereby, I can hear a clicking sound and it lights up. However, it will turn off immediately. I disconnected everything (including all speakers) from the amp, but the amp still doesn't stay on.

Does anyone have any idea what component/s may have blown?
 

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Daniel 70

Standard Member
I have an Aiwa stacking system, and I'm afraid that I may have overloaded the AIWA MX-D91MK stereo integrated Amplifier/graphic equaliser by adding 2 small speakers (presumably wrong impedance) to the surround sound. When I turn the amp on, it activates; whereby, I can hear a clicking sound and it lights up. However, it will turn off immediately. I disconnected everything (including all speakers) from the amp, but the amp still doesn't stay on.

Does anyone have any idea what component/s may have blown?
Probably an output transistor , the circuitry powers up and after a second or so delay it ,to stop the speaker whoosh, it applies power to the output stage. Then it detects a dc voltage on the speaker output terminal , which would burn out the speaker coil, and switches off. Unfortunately that era device probably has an encapsulated amplifier module ..a big plastic rectangular bit with a number of pins,so is not repairable.
 

Countfox

Novice Member
Probably an output transistor , the circuitry powers up and after a second or so delay it ,to stop the speaker whoosh, it applies power to the output stage. Then it detects a dc voltage on the speaker output terminal , which would burn out the speaker coil, and switches off. Unfortunately that era device probably has an encapsulated amplifier module ..a big plastic rectangular bit with a number of pins,so is not repairable.
I forgot to mention; when I connect the graphic equaliser to the amp, I hear the clicking sound - every 7 seconds. When disconnected, there is no clicking sound.
 

JayCee

Distinguished Member
That “big plastic rectangular bit” that Daniel 70 mentioned will probably be an “STK”-type integrated output IC...they are replaceable if you’re comfortable working with electronic components and are experienced in soldering/de-soldering neatly.
 

Countfox

Novice Member
That “big plastic rectangular bit” that Daniel 70 mentioned will probably be an “STK”-type integrated output IC...they are replaceable if you’re comfortable working with electronic components and are experienced in soldering/de-soldering neatly.
Yes, I'm experienced and comfortable... Where might I buy the component from, and what do I ask for? However, didn't Daniel 70 also said; it's not repairable?
 

JayCee

Distinguished Member
You need to take it apart and identify the output IC...it will be bolted to a large heatsink...the type no may start with “STK” followed by some digits.
Google for the part or try Farnell...you'll also need some heatsink compound/Thermal paste.
 

Daniel 70

Standard Member
Yes, I'm experienced and comfortable... Where might I buy the component from, and what do I ask for? However, didn't Daniel 70 also said; it's not repairable?
The "Chip" is not repairable, but it is replaceable. However they are unlikely to be available... They are basically a entire power stage, with voltage amplifier, driver stages and output stages.
 

Countfox

Novice Member
You need to take it apart and identify the output IC...it will be bolted to a large heatsink...the type no may start with “STK” followed by some digits.
Google for the part or try Farnell...you'll also need some heatsink compound/Thermal paste.
I'll get on it. Thanks for that...
 

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