| Started tweeking but help needed [message #2176] |
Thu, 09 April 2009 16:43  |
Amanda
Messages: 2
Registered: April 2009
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Junior Member |
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Hello,
Please can you help.
I am working on a Nocto Loco kit, all parts assembled but no signals are going through it, I'm not getting sound out or an illuminated LED. I've started the process of tweeking with regards to the power supply indicated in your PDF instructions as when I measure from ground to (what i believe to be) leg 3 of 7805 I'm receiving 11.5V (DC). There is no reading between leg's 2 and 1 of the 7805. I am using a 9V DC plug Stadium model PS9600 (which doesn't clearly state if it is negative/positive centered) and running this through an adaptor to the mains in the UK. I'm not clear what the 7809 is (mentioned in the PDF), if it is relevant, or simply means the 7805, the instructions mention this might have blown? Does this explain the high voltage? Also, no parts appear to be heating up.
Any advice much appreciated, can't wait to get going with it.
Cheers,
Amanda
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| Re: Started tweeking but help needed [message #2177] |
Sun, 12 April 2009 14:36  |
 dann
Messages: 829
Registered: December 2002
Location: Austin TX |
Senior Member |
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The "Tweaking Power" PDF that you're referring to was written for the large 7809 voltage regulator style, until now I hadn't updated it for the Nocto's small 7805 voltage regulator... so the pinout is different. I'm guessing that what you're calling pin 3 is actually pin 1 and vice-versa. When you're looking at the 7805 so that you can read the words on its face, the pins are 3-2-1, left to right.
See the updated "Tweaking Power" PDF for a picture:
http://www.commonsound.com/other/tweakingpower.pdf
So on the 7805 you get no voltage between pins 2 and 3 (center and left pins), but you get 11.5V between legs 2 and 1 (center and right pins)? The 11.5V on pin 1 is probably correct, that's the voltage coming from the powersupply. If you're in doubt about this, measure the voltage on the powersupply directly (it should be 11.5V).
If you're getting voltage going into the 7805 (on pin 1), but no voltage coming out of it (on pin 3), then the 7805 may be fried. To test, disconnect pin 3 from the board and see if you now get a voltage between pins 2 and 3.
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| Re: Started tweeking but help needed [message #2233] |
Wed, 20 May 2009 07:11 |
Amanda
Messages: 2
Registered: April 2009
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Junior Member |
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Hi Dann,
Thanks for your reply. I replaced the voltage regulator and all seemed well (as I was measuring the volts getting the correct readings) until it starting heating up. The voltage regulator is once again fried so am replacing that. I think my power adaptor might be wrong (guessing centre positive). I'm looking into getting a definite centre negative one but don't know what mA it should be. Please can you let me know.
Amanda
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| Re: Started tweeking but help needed [message #2235] |
Wed, 20 May 2009 10:52 |
dann
Messages: 829
Registered: December 2002
Location: Austin TX |
Senior Member |
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Well, if you got the correct voltage readings then you were using the correct power supply. Unless you wired the power jack a special way, that would be a center negative power supply, 9VDC, anything 150mA or more (it's hard to find a ps with less than 150mA)
It's really super easy to tell if you powersupply is center negative or positive. Just put the multimeter leads on the end of the plug and measure DC volts. If you get a negative voltage reading, then switch the red/black leads. Now if the black lead is on the center pin of the plug, it's center negative. If the red lead is in the center, it's center positive.
How long did it take for something to get hot?? Is it possible that you moved it or somehow something shifted and it shorted out momentarily? I've seen that happen before...
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