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Old 4th March 2012, 07:30 PM   #91
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Originally Posted by Zen Mod View Post
wrong polarity , Bubba .

you need pair of 2SJ74BL

but - most important - you need either to little more learn basic electronic , or little more learn how to build strictly by the book ( if not in the mood for learning electronic)
Efff -- are you serious.. i got a matched pair of 2SJ74 in the datasheet photocopy under the lettering it also says 2SK170. Same fet?!

the writing on the fets is K170.
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Old 4th March 2012, 07:48 PM   #92
generg is offline generg  Germany
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one SJ109 can only be replaced by two SJ74 no SK170 possible, with SK170 the circuit cannot work....
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Old 4th March 2012, 07:55 PM   #93
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one SJ109 can only be replaced by two SJ74 no SK170 possible, with SK170 the circuit cannot work....
wow.. really i did not know
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Old 4th March 2012, 08:38 PM   #94
generg is offline generg  Germany
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SJ types and SK types have (always) opposite polarity.....

You have a good chance your circuit will work when you replace the SK170!

Good luck!
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Old 4th March 2012, 08:54 PM   #95
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Originally Posted by BScorner View Post
Efff -- are you serious.. i got a matched pair of 2SJ74 in the datasheet photocopy under the lettering it also says 2SK170. Same fet?!

the writing on the fets is K170.
have you maybe got matched pair of SJ74/SK170?
thats not the same.
you need 2 pair of matched SJ74. one pair pr ch.
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Old 6th March 2012, 08:11 AM   #96
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thanks guys used 74BL and works now... J09's were fake.

I have 2vdc offset on speaker output how do I lower this?
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Old 6th March 2012, 12:26 PM   #97
generg is offline generg  Germany
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Do you have the voltages over R7 and R8 mentioned in the scheme?

Click the image to open in full size.


There can be different reasons......
Are your J74 a bit matched on Idss?

If you replace R7 by a pot of 1kOhm it might be possible to adjust the offset.
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