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Old 27th March 2011, 07:37 PM   #1
tony Ma is offline tony Ma  United States
diyAudio Member
Join Date: Feb 2011
Default Help me pls with B&K st-140

Hi there I need helps on my old B&K ST-140
Suddenly my power amp went dead and these are what I did already
  • Replacing each side with new 2sk135 and 2sj50
  • Replacing each side with new 2N3440 and 2N5416
  • Replacing each side with new 100uF/100V and 47uF power supply electrolytics (silmic elna)
but still the there is sound coming out. I did check the BIG capacitor and there is a current over there. After I plug in, there is about 63 V still store in cap.

Any one can help me? Any idea why this amp still dead?
I am suspecting my rectifier might have a problem.
I could not find any replacement yet for this one (FPI4020W)
FPI4020W pdf, FPI4020W description, FPI4020W datasheets, FPI4020W view ::: ALLDATASHEET :::
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Old 28th March 2011, 02:06 AM   #2
tony Ma is offline tony Ma  United States
diyAudio Member
Join Date: Feb 2011
Any one can suggest me with PS replacement? I think I found the schematic
Any one can help me with PS design using the tyrodial from this B&K? tks so much
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Old 29th March 2011, 03:48 PM   #3
tony Ma is offline tony Ma  United States
diyAudio Member
Join Date: Feb 2011
any one can recommends repair in OC or LA area?
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Old 5th May 2012, 03:03 PM   #4
diyAudio Member
Join Date: Oct 2011
Location: Chicagoland
I recently replaced a bridge rectifier in my B&K ST-140 - big improvement. Purchased from Parts Connexion:

Item Number: SEMI-68495

This definitely works and is much faster than the stock rectifier.

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