BGW Model 200 ...lazy left channel (??) - diyAudio
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Old 8th July 2009, 02:55 PM   #1
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Default BGW Model 200 ...lazy left channel (??)

I bought a BGW Model 200, used $25.
One channel is fine, the other is weak, and slightly distorted.

I have traced a signal on the inputs (w/sine wave)

..balanced input >> NE5532 unbalancing circuit >> potentiometer >> amp circuit input

And all seems fine there, both channels give the same results.
It's on the outputs that they differ, and I am not sure on how (where) to trace the rest of the amplifier circuit....I don't have a schematic.
I could measure and compare EVERY transistor...working channel vs. sick channel.

Any ideas where to start ??

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=RR=
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Old 9th July 2009, 08:08 AM   #2
h_a is offline h_a  Europe
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I would first check the output transistors; if they got fried and their base is shorted to emitter that could show the same effects as you tell (drivers feeding the speaker, no power and much distortion).

Also, one of the more often occuring accidents are to short the speaker outputs, which also often kills the output transistors.

Have fun, Hannes
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Old 1st September 2009, 06:21 AM   #3
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Update...
Tested transistors as h_a suggested.
All seemed fine.

However...I did see that there was a missing resistor R114 (@1.54k).
Then, turning the unit around...heard a loose object rattling around under the circuit board.
Guess what it was.....a 1.54k ohm resistor, with pre-bent, unsoldered leads.
So I soldered it in, and praise-be-Allah... it works.

Why was it never soldered in ?? Maybe the former (Sony studios) tech was about to do this, and dropped/lost the resistor under the board, couldn't retrieve it, and shelved the unit indefinitely. (this board seems like a PIA to remove).

=R=
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