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problem with power, J4 no voltage??
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problem with power, J4 no voltage??

by beno on Thu Jul 06, 2006 11:40 am

hi, here is my problem.i am doing the 1st section called power, I have soldered everything needed, but I am not getting any voltage across the j4 pins. I got the voltage of around 6V for C1 cap, so I'm guessing something has gone wrong since then.

also; voltage across the diodes D44-D47 doesn't register , perhaps this is the problem?

everything is soldered in correctly, and is the right voltage

please help!
beno
 
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by beno on Thu Jul 06, 2006 11:57 am

also the voltage across c5 is only about 0.2v! I don't know what is wrong
beno
 
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by guest on Thu Jul 06, 2006 10:29 pm

are you using the wallwart that came with the x0x
it sounds like you may have a dc wallwart
or some of the diodes like d42 or d43 in backwards
is anything getting hot
guest
 
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by beno on Fri Jul 07, 2006 6:08 am

oh yeh, thanks man! I had a 500mA adaptor at home, turns out it's DC output. I hope this hasn't effected anything on the board :oops:

edit: Ok, I bought a 500ma 9VAC. there is the correct charge across the large caps C3/C5, and across the ceramic caps C1 and C6. however, again there is still no voltage across the diodes D44-47 and no voltage between J4 pins and R179?

thanks
beno
 
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by guest on Fri Jul 07, 2006 11:08 am

what are the voltages on all of the pins of ic23
i think there is a post out there that says
what they should be
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by beno on Sat Jul 08, 2006 5:52 pm

thanks again, here are the readouts, not what they should be at all

J4 pin1: about 1V
pin2:0
pin3:0

IC23: pin1: about 5v
pin2:around 1V
pin3:0v
pin4: about 0.1v
pin5:0v
pin6:0v
pin7:0.6v
pin8:0v

this is really frustrating :cry:
beno
 
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by guest on Sat Jul 08, 2006 6:15 pm

is ic23 in the correct orientation
with the x0x unplugged
measure the resistance across r1
and from pin8 to ground

look for shorts and solder bridges
the traces might also have been poorly silkscreened
if all else fails
see if you can desolder ic23
and remeasure the voltages at the pin pads
it sounds like something is shorting out
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by beno on Sat Jul 08, 2006 6:34 pm

Unfortunately my multimeter can't check resistance...

i socketed ic23, so i can take it out easily, these are the readouts:

pin1:0v
2:0v
3:0.1v
4:0v
5:5.2v
6:0.05v
7:0v
8:over 20v
beno
 
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by guest on Sat Jul 08, 2006 7:04 pm

those voltages look right
so either r1 is the wrong value
or the opamp is bad
or there is a short to ground on one of the pin pads

double check the color bands on r1
try swapping in the other opamp that came with the kit
the notch should point away from j4
check to see if it gets warm
unplug it if it does

there are some really cheap multimeters out there
with resistance measurement
jameco sells some for less than ten dollars
it is near impossible to debug some things without one
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by beno on Sun Jul 09, 2006 5:44 pm

ok, R1 is correct, I bought a multimeter with a resistance check, and it's 100 ohms...

so I changed the opamp, it's in correctly, and it's not getting warm

but the problem is, every time i try to measure the voltages on J4, they keep increasing/ decreasing...ie on j4 pin 1 it starts at aroiund 5v but then constantly falls to 0v, with J4 pin3 it starts low, and slowly and steadily rises, up past 14v.....perhaps this is a faulty capacitor?
beno
 
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by guest on Sun Jul 09, 2006 6:36 pm

does the voltage on the pins of the opamp also rise and fall
what are their readings with the new opamp

do the voltages rise and fall
in relation to when you last plugged it in
or in relation to when you start measuring

what happens if you measure the 12v first and then the 5v
at what rate do the values decay

if you remeasure the voltages do they come back up
or do they stay at zero
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by beno on Sun Jul 09, 2006 7:16 pm

the opamp readings do fluctuate rapidly, and it's quite hard to read them, but they are aroung:
pin1:0v
2:0v
3:0.1v
4:0v
5:5.33v constant
6:0.1v
7:0v
0.5v

the voltages seem to rise and fall in relation to when i start measuring them

it doesn't matter which of the 5v/12v you measure first...they decay/rise at around 0.2v per second

when you re-measure, they don't stay at zero, they come up with something and then start to decay again. with the J4 pins, if you measure the voltage, then take away the probes, then measure again, it seems to carry on from when you last left it to decay...if you see what i am saying

perhaps the multimeter is faulty?

this is worrying :cry:
beno
 
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by guest on Sun Jul 09, 2006 7:31 pm

does both your old and new multimeter do the same thing

you have pin8 at .5v if i read your list correctly
that would be the first point of failure
it seems as though the opamp isnt gettng any power
or that it is shorting out to ground somehow

remeasure the voltages across c5 and c8
and then turn the power off and remove the opamp
and measure the resistance to ground at all of the pins
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by beno on Mon Jul 10, 2006 10:53 am

this is the same for both meters..

c5=14v
c8=0.5v (but is around 20v when opamp is taken out)

resistances without opamp

pin1: 36000k
2: 15000k
3: no reading
4: 50 (keeps fluctuating)
5: 0.316M
6: 0.3M
7: fluctuating, not sure
8: just keeps rising and rising (in the 200k range from about 0 to over 200k)
beno
 
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by guest on Mon Jul 10, 2006 4:32 pm

the resistances look a bit odd
but not really problematic

pin3 pin6 and pin7 are all tied together
and they do not connect to ground anywhere
so they should all have the same reading
and it should be inifinite
there will be a finite resistance as c60 charges up
but it should eventually go to infinite

make sure c60 is orientated correctly

pin1 should have 4k
and pin2 should have 1.8k
im not sure why your readings for those would be so high
they seem to bee just the wrong order of magnitude

pin4 should be zero ohms as it is connected to ground


double check the resistance from pin1 to ground
and then put in a jumper from pin1 to pin8
this will load down the voltage at pin8
to see wether the power supply is not able to source the current
or that the opamp is shorting out somehow
with the jumper in place
measure the voltage across c3 c5 and c8
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Please be positive and constructive with your questions and comments.