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4th November 2012, 08:15 PM
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#102 |
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diyAudio Member
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
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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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my Papa is smarter than your Nelson ! tnx to  clean  thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb
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4th November 2012, 09:22 PM
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#104 |
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diyAudio Member
Join Date: Aug 2011
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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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4th November 2012, 09:35 PM
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#105 |
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diyAudio Member
Join Date: Jun 2004
Location: ARKANSAS
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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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If a inch of duct tape will fix it, 3 feet should fix it for life!!!! |
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4th November 2012, 09:46 PM
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#106 |
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diyAudio Member
Join Date: Aug 2011
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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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4th November 2012, 10:01 PM
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#107 |
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diyAudio Member
Join Date: Jun 2004
Location: ARKANSAS
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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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If a inch of duct tape will fix it, 3 feet should fix it for life!!!! Last edited by HIPCHECK; 4th November 2012 at 10:03 PM. |
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4th November 2012, 10:55 PM
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#109 |
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diyAudio Member
Join Date: Aug 2011
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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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