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Old 18th January 2002, 01:22 AM   #1
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Default aleph woes

greetings all,
i've been trying to debug my completed aleph5 but still have no output, except lots of DC

here's where i'm at:

ps checks out fine at the rails

everything's fine up till Q4 , with around 9 vdc at r114 in one channel. but when i measure across c-e of q4 i get nothing. is this normal or is it a failed device? i'm still getting nothing across the load resistors (1ohm) on the output mosfet banks.

i don't know what else to try!

and why am i getting ~30vdc at the outputs??!!

hope someone can help this nearly hairless newbie,

cheers,
scott
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Old 18th January 2002, 06:45 PM   #2
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Since Q4 and R14 are in parallel, the only way
you can have voltage across one and not the
other is that they are not connected.
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Old 19th January 2002, 03:22 AM   #3
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Given all the problems you've had, i'd replace the part but check all around the area for dry solder joints... as Nelson said... both those parts are in parallel and so should see the same voltage, if one is showing 0V it indicates that they are not connected be it because of a dry solder joint or because of a broken track on the pcb.
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Old 19th January 2002, 04:20 AM   #4
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i found that i mis-wired the source and sense on the output hexfets and corrected this. now, i get around 0,5 vdc at the outputs, which is a vast improvement.

i still have 33 volts at the rails, everything the right polarity. but now i'm seeing almost no voltage across the zener on the +vcc rail.???? how can this be??

and i pulled and checked all the input mosfets and they are fine. all resistors are fine as well.

i also reheated EVERY solder on both boards.

i also checked my pcb layout against the schematic very carefully.
what the !@#%$!( is going on here.?????
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Old 19th January 2002, 05:21 AM   #5
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do you have a multimeter with a diode tester??? if so turn off the amp and connect the leads of the meter to either end on the zener and measure the voltage drop if it's not what you expect it to be then you'll have to replace it.
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Old 19th January 2002, 06:04 AM   #6
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no i dont have a diode checker with my dvm. is there another way to check? it seems that the zener coming from V+ may be inhibiting current somehow. it's the only device in the front end of the amp that i haven't checked, cuz i don't know how.

thanks,
scott
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Old 19th January 2002, 06:58 AM   #7
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Sorry i'm a little bit lazy ... could you please tell me what the nominal voltage drop for this part is meant to be....
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Old 20th January 2002, 06:22 PM   #8
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in an effort to bog this forum down, i started a new thread going in a slightly differenct approach. as stated before, i'm still learning the diy forum etiquette. so, let's call this thread done.

thanks for the patience and help.

scott
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