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need help with regulators...

post #1 of 8
8/22/10 at 4:45am
Thread Starter 

... for a aune dac, ref: http://www.head-fi.org/forum/thread/505235/replace-lm1117-with-78xx-regulator#post_6824241

 

i don't think i have this figured out, need some expertise.

 

i want to replace these LM1117 with dexa super regulators, but i don't know whether to use positive or negative regulators.

 

my multimeter reads positive voltage at the LM1117 pins, but it looks like they are designated as negative as printed on the pcb.

 

i've looked at the data sheet for LM1117 - http://www.advanced-monolithic.com/pdf/ds1117.pdf , but don't know enough about this to make a decision.

 

i'm aware of the pinouts and dropout, and i think all i need to know is whether to get dexa 78xx, or 79xx.

 

AMS1117.JPG

 

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post #2 of 8
8/22/10 at 5:21am

lm117 is a positive regulator.

 

If you're getting negative voltages, you are likely measuring incorrectly (like having your probes on the wrong pins).

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post #3 of 8
8/22/10 at 5:30am
Thread Starter 

thanks, but that's not much help.

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post #4 of 8
8/22/10 at 6:04am
What cobalt means is that your 1117 regs are both positive regs, and you're measuring them with your dmm probes backwards. Give us a link to the dexa regs you are thinking about using.
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post #5 of 8
8/22/10 at 6:24am

They're positive - the "negative" signs on the PCB are just hyphens...

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post #6 of 8
8/22/10 at 6:45am
Thread Starter 
Quote:
Originally Posted by guzzler View Post

They're positive - the "negative" signs on the PCB are just hyphens...

ok, thats what was throwing me :)

 

thanks alot y'all.

 

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post #7 of 8
8/22/10 at 6:51am
You probably know the 1117 and 780x don't have the same pinouts. If you flip the 780x so the input is the same and then cross the output and ground pins it will match the 1117.

1117 = G O I
780x = I G O
Edited by digger945 - 8/22/10 at 6:53am
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post #8 of 8
8/22/10 at 6:59am
Thread Starter 

yep, thanks :)

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