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Old 4th November 2012, 08:07 PM   #101
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Quote:
Originally Posted by Zen Mod View Post
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Thanks! But I have -50mV, not +50, will this trick work foe me?
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Old 4th November 2012, 08:15 PM   #102
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which trick ?


replace R11 (looking at original A60 sch, posted in #1) with series connection of 150R fixed resistor and 100R multiturn trimpot ; vary it and you'll get 0 on output , at temp. equilibrium

both inputs grounded during setting procedure
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Old 4th November 2012, 08:39 PM   #103
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Oh, thanks! I thought it is all about R8*( comment on 8Mohm there).
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Old 4th November 2012, 09:22 PM   #104
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Ok, guys, I have a bigger problem -- There is only 4V between -V and -G on the board (and negative daughter boards, respectively). Everything is ok(~28v) on the positive side. PSU gives 33V to the board.

Any ideas? Could I damage input transistors while soldering? I really need your help as it is my first ss DIY serious amp!
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Old 4th November 2012, 09:35 PM   #105
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well at 10:45 last night you were power up the supply, and now I see a almost done amp...You had to be hard at it to get to this point, now take a break and watch a football game. Think about it and come back. Then start with all wire connections.

Meanwhile the thread will get some replies on where to look, also

Steve
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Old 4th November 2012, 09:46 PM   #106
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Thanks Steve :-). I'll try a little bit more: i have 28.5 V between -G and ground. On the positive part its only 4V...hm...

I tested input transistors with multimeter I get some readings if i touch: neg. on source then switch pos. from gate to source.
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Old 4th November 2012, 10:01 PM   #107
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Here is my own example of finding problems after a night of "putting it all together" It was simple, ground wire wrong place, seems kinda funny now. It worked on the bench, and then.....

The Mini-A

Now it runs smooth. We have all had those days.



Steve

Do you have 9V across Z5?
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Last edited by HIPCHECK; 4th November 2012 at 10:03 PM.
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Old 4th November 2012, 10:02 PM   #108
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Funny, my plays music but very quiet :-)
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Old 4th November 2012, 10:55 PM   #109
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Hm, or there should be 4.8V between -G and -V as it is exactly voltage drop on R14(18).
The thing is, it is extremely quiet even with my pioneer hpm which are 95db sensitive...
Another, i run it for an hour(played led zeppelin 2,4) and it is not even close to the temperature i expected, it is like 40-45C max. Voltage across source resistors 0,34V(should be .37V according to A60 schem.)
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Old 4th November 2012, 11:05 PM   #110
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Balanced or single ended input? What source? etc
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