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tony Ma 3rd January 2013 10:15 PM

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

really appreciated


win33 4th January 2013 01:14 AM

Schematic Bk Component
I have it,drop your email

tony Ma 6th January 2013 04:33 AM

Win, I PM'ed you my email address.

Pls send me

tks so much

destroyer X 6th January 2013 06:32 AM

This one needs a lot of tweaking to perform high end
2 Attachment(s)
A very big and heavy empty box.

good luck!


Struth 13th January 2013 07:37 PM

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

tony Ma 25th January 2013 08:56 PM

This is what I got from the factory
1 Attachment(s)
Get in touch with the factory by email
This is what I got from them

reedcat 25th August 2017 04:59 AM

Does anyone know what transformer and capacitors are inside? I am thinking of using an old ST140 for parts/chassis...

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