First off, measure the output of your AC adapter with it unplugged from the O2. Put your meter on 20V AC (upper right part of the dial, make sure it is not the DC setting in the upper left dial) setting and measure what is coming out of the adapter. Make sure the adaptor is plugged into the wall, of course. If your adaptor has different voltage settings like raspunsen's did, use the "16VAC" setting. If your meter doesn't give a result try the next highest 200V AC range. Your adapter may be putting out more than 20V AC.
Then if that works, make sure the O2 power switch is off and plug the power adapter into the O2, and make sure it is plugged into the wall, of course. Put your meter on the 20V dc setting now (upper left part of the dial) and measure from ground with the black lead (metal shell of the gain switch) to the lead of diode D3 with the band (furthest from the board edge). That should be around +24.9Vdc, like raspunsen got. Then measure from ground (using the black meter lead again) to the lead of diode D4 without the band (the end farthest from the on/off switch). That should read around -24.7Vdc.
Post back on those measurements.
Last edited:
If all that fails, take a voltage reading between ground (gain switch shell) and the cathode lead (with the band, farthest from board edge) of D3. Depends on what your input voltage is, but with 16VAC in you should get somewhere around +24.9Vdc, plus or minus a volt. If that is good then test ground to the anode side (end closest to the regulator) of D1. That should be around +12Vdc. If you get the +24.9Vdc on the first reading but no +12Vdc on the second, then your U5 regulator is bad.
Well, I did this test and got 19.1 on the first test and 0.00 on teh second test. Does this mean my U5 regulator is bad? Since this happened to another guy, do you think it could be a bad batch at Mouser. Or do you think it is easily static damaged and that we didn't care for it enough? Please help because I'd like to get this working ASAP.
Well, I did this test and got 19.1 on the first test and 0.00 on teh second test. Does this mean my U5 regulator is bad? Since this happened to another guy, do you think it could be a bad batch at Mouser. Or do you think it is easily static damaged and that we didn't care for it enough? Please help because I'd like to get this working ASAP.
+19Vdc may be OK for the reading on D3 if your adapter is putting out 12VAC rather than 16VAC like raspunsen's. Please do that first test I wrote above about checking the AC voltage coming out of your adapter plug. Also just see what it says on the adapter about how many output volts and how much current it is rated for.
But... the reading on D1 should be +12Vdc, like I wrote for raspunsen, and not 0Vdc. Yes, that does sound like another bad U5, or a short from the regulator to ground, but if you have replaced it then it wouldn't be very likely to have 2 bad ones.
Well, this is harder, but see if you can measure the voltage from ground (metal shell of the gain switch) to all 3 legs of U5 and post what you get. Might be easiest to flip the board over and make the tests on the back of the board, but be very careful not to short between the leads with your test probe.
The lead of U5 that is closest to the on/off switch connects to the banded end of D3, where you measured the +19Vdc. So you should get +19Vdc on that lead unless a PC trace is broken.
The middle lead of U5 connects to ground, so you should get OVdc there.
The lead of U5 farthest from the on/off switch connects to D1, so you should get 0V there like you are getting on D1 if U5 isn't working.
Also - how hot is U5 getting? Another way to get 0V out is a short from the output to ground, like a solder bridge from the middle lead of U5 to the lead farthest from the on/off switch. To test for this, unplug the power from the O2 and let it sit 10 minutes for the capacitors to discharge. Then put you meter on 20 ohms or so and check the resistance from the middle U5 lead (black wire on that) to the U5 lead on either side.
I get 0 voltage on each of the U5 leads. That pretty much means that Mouser is sending out bad U5's right? There is no way to fix this unless the U5 is working and I can't run it on AC power unless that stupid thing is working right? What do you think I should do because I am making this for a guy who isn't planning on using batteries with it and I wasn't planning to do it on mine either. PLEASE HELP as soon as you can. Thanks again for all the help!
If you are getting +19Vdc on the banded end of D3 to ground, but you are getting 0Vdc on all three pins of U5 to ground, then the problem is not U5. The banded end of D3 is directly connected to one of the U5 pins with a PC board trace. You either have a broken PC trace, or you didn't have the AC adapter plugged in when you made your voltage measurements on the U5 pins.
To find out if you have a shorted trace to ground on the regulator output, you would need to do those resistance measurements I posted above, with the O2 adaptor unplugged, from the middle pin of U5 to the pins on either side. From the middle pin to the pin closest to the on/off switch you should get something like 2 megohmms (2 million ohms). You would need your meter on the highest resistance scale to measure that. Then from the middle pin to the U5 pin on the other end you should get something like 33Kohms. Your meter would need to be on the 200k range to measure that. If you get 0 ohms with either test you have a shorted PC trace to ground.
I'm starting to think that maybe you damaged the PC board solder mask around one of the part leads with soldering iron heat, like maybe the lead of C6 which is closest to D1, which is allowing the solder to short to the ground plane and hence short the output of U5. If you measure 0 ohms from the non-banded side of diode D1 to ground then that is what has happened. To fix that you would have to suck up all the solder on that bad with copper de-soldering braid, then re-solder being very care to use only enough solder to barely cover the pad and solder the wire on all sides. There is no need for a "ball" of solder on a pad. That much is excessive.
Either the MC7812 or MC7809 work fine with AC. With the MC7809 and MC7909 you would have +/-9V rails which would not be high enough to charge the batteries, so "AC only" just because the batteries wouldn't charge. But what you have now, the 12V regulators, are just fine for AC.
To find out if you have a shorted trace to ground on the regulator output, you would need to do those resistance measurements I posted above, with the O2 adaptor unplugged, from the middle pin of U5 to the pins on either side. From the middle pin to the pin closest to the on/off switch you should get something like 2 megohmms (2 million ohms). You would need your meter on the highest resistance scale to measure that. Then from the middle pin to the U5 pin on the other end you should get something like 33Kohms. Your meter would need to be on the 200k range to measure that. If you get 0 ohms with either test you have a shorted PC trace to ground.
I'm starting to think that maybe you damaged the PC board solder mask around one of the part leads with soldering iron heat, like maybe the lead of C6 which is closest to D1, which is allowing the solder to short to the ground plane and hence short the output of U5. If you measure 0 ohms from the non-banded side of diode D1 to ground then that is what has happened. To fix that you would have to suck up all the solder on that bad with copper de-soldering braid, then re-solder being very care to use only enough solder to barely cover the pad and solder the wire on all sides. There is no need for a "ball" of solder on a pad. That much is excessive.
Either the MC7812 or MC7809 work fine with AC. With the MC7809 and MC7909 you would have +/-9V rails which would not be high enough to charge the batteries, so "AC only" just because the batteries wouldn't charge. But what you have now, the 12V regulators, are just fine for AC.
Last edited:
I don't see a broken PC trace, but it looks like the U5 connects to the C6 and the D3 connects right to the AC adapter input. I tested the U5 bands one by one with the AC power plug in and got no readings from either. Did you mean put the red lead on all 3 pins at once or seperate because I did it seperate? That leads me to figure a short to ground on that trace. That probably sounds like what it is because there is no way two U5 are bad and I know I tested each peg correct. Please help further.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Look at U5 to the left of it. Is that U6. Look at the bottom of U6, does that look like the bottom pin is connected to the pin below it? I could have sword I didn't see this with my eye and the flash caught it. Is this my problem?
NEVERMIND, IT JUST LOOKS LIKE THIS BECAUSE THAT PIN EXTENDS UPWARD AND OUT TO MAKE IT LOOK LIKE THAT. PLEASE HELP!!!!
NEVERMIND, IT JUST LOOKS LIKE THIS BECAUSE THAT PIN EXTENDS UPWARD AND OUT TO MAKE IT LOOK LIKE THAT. PLEASE HELP!!!!
Last edited:
Red lead is only one one pin at a time! Don't use the meter probe on more than one pin or you will short things out.
Yes, that is how it goes, one adaptor pins connects to the unbanded side of D3, so there should be zero ohms between those two points. Then the banded side of D3 connects to the top outer pin of U5, so there should be zero ohms between those two points. You can follow the traces on the top and bottom and use your meter on the lowest resistance range, like 20ohms or 2 ohms, to check if traces are OK like this - with the O2 power off. Always unplug the ac adaptor from the O2 when doing resistance readings. You only need the ac adaptor plugged in for voltage readings.
Yes, that is how it goes, one adaptor pins connects to the unbanded side of D3, so there should be zero ohms between those two points. Then the banded side of D3 connects to the top outer pin of U5, so there should be zero ohms between those two points. You can follow the traces on the top and bottom and use your meter on the lowest resistance range, like 20ohms or 2 ohms, to check if traces are OK like this - with the O2 power off. Always unplug the ac adaptor from the O2 when doing resistance readings. You only need the ac adaptor plugged in for voltage readings.
Whoops - ignore my comment above about the solder mask. I was going by the board layout diagram. The O2 has a ground plane on top, but not on the bottom where you solder so it would be harder to short to the ground plane.
From your photo though I see a lot of what looks like solder bridges that shouldn't be there. Like the top pad of C6 has solder slopping over another trace to the right of it. You should clean up any solder like that with solder wick. Solder should not be bridging any pads or traces. C6 is to the right of U5 in your photo. To the left of U6 I see another bunch of solder bridging over from C7 (to the left of U6) to the trace to the right of it.
Batteries will not charge correctly if the AC power supply in the O2 isn't working.
From your photo though I see a lot of what looks like solder bridges that shouldn't be there. Like the top pad of C6 has solder slopping over another trace to the right of it. You should clean up any solder like that with solder wick. Solder should not be bridging any pads or traces. C6 is to the right of U5 in your photo. To the left of U6 I see another bunch of solder bridging over from C7 (to the left of U6) to the trace to the right of it.
Batteries will not charge correctly if the AC power supply in the O2 isn't working.
Last edited:
Those solder bridges like the one on the top left and the one to the left of the U5 underneath are just the pins extended and then bended over near that piece that makes them look like bridges. They really aren't touching at all in the real thing I checked them all. The top part of C6 does have a little bubble underneath, but I can assure you it's not touching U5 at all.
Yeah, I just figured that out after pondering the photo a bit more. The angle of the photo just makes them look like shorts. Well good!
Well what I would suggest here is the resistance readings I posted above to check continuity of your traces. With the O2 unplugged and the meter in the low ohms range just test that trace from one of the adaptor jack pins to D3. Should be zero ohms. Then the other side of D3 to one of the U5 pins also zero ohms. Then D1 to the U5 pin on the other end, also zero ohms if all those connecting traces are good. And in each case measure the trace to ground - that should not be zero ohms, or you have a short to ground.
Because.. you measured +19Vdc to ground once on the banded end of D3. And if your resistance test here shows there is zero ohms (a good PC board trace) from the banded end of D3 to the pin of U5 closest to D3, then that U5 pin also has to be +19Vdc, which you were not getting. So figure that one out first!
Well what I would suggest here is the resistance readings I posted above to check continuity of your traces. With the O2 unplugged and the meter in the low ohms range just test that trace from one of the adaptor jack pins to D3. Should be zero ohms. Then the other side of D3 to one of the U5 pins also zero ohms. Then D1 to the U5 pin on the other end, also zero ohms if all those connecting traces are good. And in each case measure the trace to ground - that should not be zero ohms, or you have a short to ground.
Because.. you measured +19Vdc to ground once on the banded end of D3. And if your resistance test here shows there is zero ohms (a good PC board trace) from the banded end of D3 to the pin of U5 closest to D3, then that U5 pin also has to be +19Vdc, which you were not getting. So figure that one out first!
Last edited:
Alright. I did the test between the D3, the power adapter jack, and the U5 pin. The first way with the ground on the D3 and the red lead on the other pins i got .001 and .000. Then when I switched it I got a 1.4 and a .8 and .000 in the U5 pins and .001 and 1.4 I think on the power adapter pins. It might have been the other way around though with the ground on the U5 pins when I got the .001 and .000 readings. But both ways those were the readings and I didn't know which one was legit since I didn't know where to put the leads to. The middle pin read .000 of the U5 when I did it the other way around. Does that mean that one is bad? That is the one where it looked a little too burnt to me.
Wait a minute. I just had another idea from looking at the O2 pc board trace diagrams on top and bottom.
There actually is a way for the trace from the banded end of D3 to U5 to be broken. That square pad on the banded end of D3 is a "via hole", which is a plated connection that connects the back of the PC board to the front of the PC board at that point. Sometimes those don't work quite right, in which case even though you soldered the banded end of D3 on the bottom of the board the voltage may not make it to the trace on the top. I also just remembered that raspunsen posted something about reading 8V on the lead of the diode, but +24volts on the square pad around it.
Try this. Solder the lead on the banded end of D3 on the TOP of the board, to that square around it, in addition to the soldering you have done underneath the board on that lead. Then see if that fixes anything. That would get around a bad via hole.
There actually is a way for the trace from the banded end of D3 to U5 to be broken. That square pad on the banded end of D3 is a "via hole", which is a plated connection that connects the back of the PC board to the front of the PC board at that point. Sometimes those don't work quite right, in which case even though you soldered the banded end of D3 on the bottom of the board the voltage may not make it to the trace on the top. I also just remembered that raspunsen posted something about reading 8V on the lead of the diode, but +24volts on the square pad around it.
Try this. Solder the lead on the banded end of D3 on the TOP of the board, to that square around it, in addition to the soldering you have done underneath the board on that lead. Then see if that fixes anything. That would get around a bad via hole.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.