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Old 3rd January 2013, 10:15 PM   #1
tony Ma is offline tony Ma  United States
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Default b&K St-140 schematic

any one has schematic for B&K st-140?

really appreciated

tks
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Old 4th January 2013, 01:14 AM   #2
win33 is offline win33  Indonesia
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Default Schematic Bk Component

I have it,drop your email
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Old 6th January 2013, 04:33 AM   #3
tony Ma is offline tony Ma  United States
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Win, I PM'ed you my email address.

Pls send me

tks so much
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Old 6th January 2013, 06:32 AM   #4
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Default This one needs a lot of tweaking to perform high end

A very big and heavy empty box.

good luck!

Carlos
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File Type: jpg st140.jpg (46.6 KB, 240 views)
File Type: jpg DSC01832.JPG (127.6 KB, 231 views)
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Old 13th January 2013, 07:37 PM   #5
Struth is offline Struth  Canada
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Hi Guys

The schematic they showed me and that I verified by tracing the circuit back in 1981 was a bit more complex. At that time, they used six dual-transistor cans - 2N2920npn and 2N3811pnp. The circuit is essentially as above: a PNP input loaded by a four-BJT Widlar current mirror; feeding a Darlington VAS that had a current-mirror to load the input transistor and quickly discharge the base of the output; constant current sources for the input comprised of dual BJTs with a cross-collector degeneration resistor; current source load for VAS; mosfet output as above.

A friend and I showed them an alternate way to lay the amp out and an alternate circuit using all-discrete BJTs. Maybe they saw the cost savings of dumping the duals?

Their original schemo was on a folded piece of paper with a pencil-drawn circuit on it. The circuit follows standard lines but I suspect they borrowed the details from someone else. A few years later the original designer left and was replaced by a young Asian guy who could also design tuners and suchlike allowing them to expand their product range.

Have fun
Kevin O'Connor
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Old 25th January 2013, 08:56 PM   #6
tony Ma is offline tony Ma  United States
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Default This is what I got from the factory

Get in touch with the factory by email
This is what I got from them
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File Type: pdf St140 Amp Schematic.pdf (636.3 KB, 138 views)
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