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Old 12th October 2004, 04:55 AM   #1
Greg F is offline Greg F  Australia
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Default Help please Sub Amp P68 from ESP

Hi Guys,

Hope you can help ...

Have assembled P68 from ESP

I'am using two 12Vdc 500mA plug packs to reach 21v +/- for testing with 22ohm 10w W/wound resistors ...

Get 16.8Vdc before resistors when hooked up to Amp
Current return is 6.7 + & - rail ??

But the main problem is - 4v @ output, lifted resistors R18,19,20,21 still getting - 4v then lifted R16,17 got - 6.7v

Not shore If this is do damage to other components ??

So the only power is from Q3 base if possible or D2,3 through C5 to the output ??

Also D1 always lights up but where is the current coming from ?? Q1 base ??

Any suggestion

Greg ...

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Old 12th October 2004, 09:30 AM   #2
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What is the voltage drop over the two 1 Ohm resistors.. is there any bias current flowing?
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Old 12th October 2004, 12:15 PM   #3
hjelm is offline hjelm  Sweden
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D1 lights up since the current goes from ground, r23, r8, D1, to -12V
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Old 13th October 2004, 12:11 AM   #4
Greg F is offline Greg F  Australia
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Join Date: Oct 2004

Didn't check that, I power down once output & return current was measured ...
Would it help to locate problem If I hooked everything back up and check that current ??


So LED can be power from - rail, that explains it ... thks ...

Greg ...
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