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Old 16th March 2008, 12:28 PM   #1
ManUtd is offline ManUtd  Norway
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Default JM Lab Electra SW-900

I am looking for scematic of this active subwoofer.
It has an built in amplifier (China amp ~150W)
When i first looked inside i was suprised about the PCB boards.
It looks like it is built on cheap pcb boards (poor quality pcb).

Amp is defective.It has short circuit in output stage (2SC5200 and 2SA1943, also drivers are defective.Element looks ok,~4ohm.Emitter resistors are 0,1Ohm 5W.What could be a good bias current? in this circumstance?

Most important is to obtain the service scematics,anyone got an copy?

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ManUtd.
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Old 16th March 2008, 10:28 PM   #2
ManUtd is offline ManUtd  Norway
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Join Date: Sep 2003
Location: Hof,Norway with Nice Mountains!
Default Change of drivertype

Drivers in this amp is 2SB649A and 2SD669A they were also to be changed(defective).Is there any good replacement for this drivers as i do not have them here? I have 2SB648A and 2SB668A but spec is not the same on the collector current.Also got some pairs of MJE15031 and MJE15030, BD139-40,bd143-44.
Any idea what i can use as replacement drivers?

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ManUtd
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Old 16th March 2008, 10:47 PM   #3
ManUtd is offline ManUtd  Norway
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Default Replacement

Just found some good spares here:
Could i replace the 2sc5200/2sa1943 with a pair of MJL4281/MJL1302? or MJL21193/21194? and use the MJE15030/15031 as drivers?

Please help as i need to get my sub up working again, hopefully work longer also.

regards,
ManUtd
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