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12th June 2005, 02:55 PM
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#1 |
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diyAudio Member
Join Date: Jun 2003
Location: Italy
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p3a problem
I've built some p3a board but some of them don't run correctly...
Without output transistor i've negative rail at the output... ANy ideas? If i connect positive and negative i've negative rail at output.. If i connect only positive i've a small positive at output... If i connect only negative i've full negative at output... |
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12th June 2005, 03:07 PM
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#2 |
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diyAudio Member
Join Date: Sep 2002
Location: near Milano , Italy
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It seems that you could have a short somewhere or a transistor inserted the wrong way.... if you don't show us a pic I'm afraid we can't help much.
A pic of the board might do, even better to check the node voltages and send a pic of the schematic with the values written on the nodes. Did you draw the boards yourself? BTW it is better, to avoid damages, to provide supply voltages through a 100 Ohm 3-5W resistor per rail when testing amplifiers the first time. Ciao Andrea
__________________
I don't believe in audiophile components - except when I can get them at frugal-phile(tm) prices 
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12th June 2005, 05:37 PM
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#4 |
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diyAudio Moderator
Join Date: Apr 2002
Location: Chatham, England
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Well, at first glance, it looks like the legs of the LCD are shorted...
__________________
Al The miracle is not to fly in the air, or to walk on the water; but to walk on the earth. Chinese Proverb |
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12th June 2005, 06:32 PM
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#6 |
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diyAudio Member
Join Date: Aug 2002
Location: Farmington, CT
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According to that schematic, you've got +30v AND -30V in the SAME PLACE on BC546. Two different voltages can't exist at the same time in the same place. I'm not great w/ terminology but it looks like thats the base of bc546 thats got both +30v and -30v at the same time...so which is it?
-Matthew K. Olson |
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12th June 2005, 06:54 PM
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#8 | |
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diyAudio Member
Join Date: Jun 2003
Location: Italy
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According to that schematic, you've got +30v AND -30V in the SAME PLACE on BC546. Two different voltages can't exist at the same time in the same place. I'm not great w/ terminology but it looks like thats the base of bc546 thats got both +30v and -30v at the same time...so which is it?
-Matthew K. Olson [/QUOTE] NOOO!  One reffer to base and the other reffer emitter.Quote:
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12th June 2005, 07:59 PM
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#10 |
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diyAudio Member
Join Date: Jul 2002
Location: Denmark - Jutland
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Q1 VBE = 60V?????
\Jens |
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