US amplifiers.

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Kaliphan
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Re: US amplifiers.

Post by Kaliphan » 17 Jul 2018, 12:03

May I suggest that you take into account my original post where I say I *WOULD NOT* recommend buying an amplifier kit where the schematic is not published?

I stand by that statement until Telstar publishes his schematics, I may well change my mind at that point but I'm ignoring your posturing until that time.

There are plenty of tests already on the net for the Chinese kit, there are, as far as I can find, none for the Telstar one.

I'm very pleased your neighbour was a GCHQ design engineer, if that's true are you sure he's happy for you to publish his name on a public forum given his ongoing commitment to the official secrets act?

Blackolive
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Re: US amplifiers.

Post by Blackolive » 19 Sep 2018, 10:05

A useful read is here

http://archive.retro.co.za/archive/Moto ... ionOCR.pdf

Ive also attached a linear amplifier circuit with biasing

Ive an X-force 200 here that needs fixing. The prvious owner put 100 watts into it, Im hoping they havent popped the power transistors and its just taken the switching circuitry out.

the "bias" arrangement on these amps is arranged by a reverse connected diode standing the base of the power transistors at 0.6 volts.
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fodendaf
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Re: US amplifiers.

Post by fodendaf » 25 Sep 2018, 20:54

I built a 2x2sc2879 powerplate amp using the ab bias with thermal tracking instructions on worldwidedx. Of course the transistors are nearly shot from being overdriven. I don't know if it's against the rules to advertise but i'm in ireland so the postage wouldn't be too bad. I have two new hgsemi pills to go in it also. It's a rough build, but it would be cheaper to rework it than build a brand new amp.

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Unit 148 Mobile
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Re: US amplifiers.

Post by Unit 148 Mobile » 14 Oct 2018, 09:56

Black Olive, that amp has Toshiba's the schematic you posted has a different device from Motorola.

Did Xfarce send you that with the amp?

If you read back through the thread I think there's a 2SC2879 Toshiba datasheet posted. With the two in that amp 15W pep is more than enough drive and to save them from being pushed into compression and the intermod distortion going AWOL.

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Blackolive
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Re: US amplifiers.

Post by Blackolive » 16 Oct 2018, 10:12

Unit 148 Mobile wrote:
14 Oct 2018, 09:56
Black Olive, that amp has Toshiba's the schematic you posted has a different device from Motorola.

Did Xfarce send you that with the amp?

If you read back through the thread I think there's a 2SC2879 Toshiba datasheet posted. With the two in that amp 15W pep is more than enough drive and to save them from being pushed into compression and the intermod distortion going AWOL.

Unit 148 Mobile

No, I contacted Xfarce for a schematic. he wanted the amp back and 200 dollars to repair. guess the yanks must be more gullible than us.

the schematic is from an application note just to illustrate a feasible bias circuit

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