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Old 24th September 2011, 02:17 PM   #901
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Originally Posted by AndrewT View Post
if you want help then post accurately !!!!!
I am not pedantic, but still you are wright
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Old 24th September 2011, 03:23 PM   #902
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Originally Posted by Josip_Del View Post
again my mistake in prefix -0.4V on bc550c side
Look Josip this design is very simple and also symmetrical, so if you read +V on positive side of the sch there should be the same -V value on the mirror side.

Beside that Vbe of the input pair should be 0,6V for each transistor and voltage across 10ohm emitter resistor should be 45mV each (4,5mA through 10 ohm). So if Vbe is 0,4V at BC550C and 0,35V at BC560C these transistors are completely off. There is probably no supply current through 1k from +/-15V to feedback loop. Every transistor now is currently off. Check the voltages across all resistors (not referenced to GND but from one pin to another pin of a resistor and show us) so we will know which currents are too low.

Be precise with values, polarity and marking, otherwise I can not help.
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Old 24th September 2011, 04:31 PM   #903
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Originally Posted by Josip_Del View Post
I am not pedantic, but still you are wright
May i suggest you to open a separated thread about your problem ?
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Old 24th September 2011, 05:18 PM   #904
Ruwe is offline Ruwe  Europe
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Josip,
You better write all voltages on the schematic. This is the way to do some troubleshooting. Put the black lead of your voltmeter to common ground (star or whatever) and take the voltage measurements at all nodes of the schematic.
Then post the schematic and people (or better LC) can send you a PM. This way it will not take pages of this thread.
I personally think that your input is probably OK (at 0.4V B-to-E transistors are already conducting), what I suspect is your output stage. Are your IRF transistors measurements correct? 31,5V to both drain and source?! If yes, they are nicely shorted
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Old 24th September 2011, 05:54 PM   #905
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Originally Posted by Esperado View Post
May i suggest you to open a separated thread about your problem ?
OK no problem but last question? voltages on Vbe transistor is changing but very little turning 1K trimmer
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Old 24th September 2011, 06:29 PM   #906
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Originally Posted by Josip_Del View Post
OK no problem but last question? voltages on Vbe transistor is changing but very little turning 1K trimmer
I do not know does this has something to do with biasing but I changed 1K resistors to 2.7K to get 28dB gain
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Old 24th September 2011, 07:02 PM   #907
AndrewT is offline AndrewT  Scotland
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I think I can see 4pr of 1k0 resistors in post1 schematic.
Which pair did you change?
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Old 25th September 2011, 04:23 AM   #908
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I rounded them up in the post #785Simple Symetrical Amplifier
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Old 25th September 2011, 05:33 AM   #909
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Originally Posted by Josip_Del View Post
I rounded them up in the post #785Simple Symetrical Amplifier
Not precise link here is better #785Simple Symetrical Amplifier

Last edited by Josip_Del; 25th September 2011 at 05:35 AM.
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Old 25th September 2011, 05:55 AM   #910
shaan is offline shaan  India
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And here I start.
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