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Old 22nd Aug 2013, 12:00 am   #18
Herald1360
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Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
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Default Re: Roberts R200- Distorted Output

Quote:
Originally Posted by TrevorG3VLF View Post
TR4 has a low emitter/base voltage. I would expect about 0.2V not 0.05V.
If it's a bit leaky, 50mV may be fine. It's a classic pot on the base and emitter resistor circuit, so the current will just rise a bit to balance emitter volts with base volts minus whatever bias is needed (strictly speaking plus here I guess since the devices are pnp).

Voltages- I guess chassis is the heavy line at the bottom of the circuit, so you would expect the bases and emitters of the output pair to be pretty close to that, since it is itself sitting at the max possible bias voltage for the pair.
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