adafruit industries

greg · Post by **greg** » Fri Nov 11, 2005 4:33 am

i am getting twice the voltage that i should be at j4:

pin1 = 12v (instead of 5.333)
pin3 = 24v (instead of 12)

any ideas?

thanks,
greg

oh, and yes i'm using the supplied 9vac adapter.

greg · Post by **greg** » Fri Nov 11, 2005 4:42 am

also,
every other test in the power supply section checks out, except for j4.
suspicious, i know.
anyone?

thanks,
greg

Guest · Post by **Guest** » Fri Nov 11, 2005 5:13 am

if nothing has blown up yet id suspect you have
your meter connected to something other than ground

what is the voltage across c8

greg · Post by **greg** » Fri Nov 11, 2005 12:09 pm

i am using pin 2 of j4 as ground.

the voltage across c8 is 26v

thanks,
greg

Guest · Post by **Guest** » Fri Nov 11, 2005 1:34 pm

check to see that ic22 is in correctly
what is the voltage at pin5 of ic23
it should be 5.333

double check r2 and r3

greg · Post by **greg** » Fri Nov 11, 2005 4:27 pm

pin 5 of ic23 is 12.2v

ic22 (lm336) is oriented correctly (broken?)

r2 is correct (1k)

r3 is correct (6.8k)

thanks,
greg

Guest · Post by **Guest** » Sat Nov 12, 2005 1:48 am

if the lm336 is orientated correctly and soldered well
then it is probably broken
measure the voltage on its three pins
should be 0v 2v and 5v approximately
and if you can measure at the actual pins and
not the solder connection
it will eliminate cold solder joint as the problem

greg · Post by **greg** » Sat Nov 12, 2005 6:25 am

aah, i wondered as much.

are these commonly available? or is there a pin-compatible replacement?

thanks a lot,
greg

Guest · Post by **Guest** » Sat Nov 12, 2005 2:29 pm

both mouser and digikey carry them

Guest · Post by **Guest** » Sat Nov 12, 2005 2:30 pm

out of curiousity
what did the voltages on the pins end up being

greg · Post by **greg** » Sun Nov 13, 2005 4:00 am

my voltage readings at the lm336 are 0v 12.5v and 10.8v.

i'm going to order another one, but for now i'm just going to use another power supply so i can continue building the rest of the box.

thanks a million for your help!

greg · Post by **greg** » Wed Nov 16, 2005 2:32 am

ok,,,
i replaced the lm336, measured 10v and 12v at j4, then touched the lm336 and it was hot enough to actually burn my fingers. looks like the problem might be originating elsewhere in the circuit.

thanks for any suggestions,
greg

greg · Post by **greg** » Wed Nov 16, 2005 2:47 am

it works! sort of. i realized that i accidentally replaced the 7806 with the new lm336. when i put it in the right place, i now get 9.49v and 4.29v at j4. that's better at least.

i've been adjusting tm6 but it only varies the voltage between 4.27 and 4.29v. somehow i'm not hitting 5.333.

any ideas?

thanks,
greg

adafruit industries

getting double voltage at j4 power supply output. ?

getting double voltage at j4 power supply output. ?