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Old 19th January 2012, 09:11 PM   #21
agdr is offline agdr  United States
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Quote:
Originally Posted by jschristian44 View Post
The guy said it's a bad regulator. Which tests with my MM can I use to test this?
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 by agdr; 19th January 2012 at 09:21 PM.
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Old 19th January 2012, 09:43 PM   #22
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I actually have 2 different ones I tested. I got the cheapest model first and the most expensive model last. So I tried both and same thing. As for D3 and D4, where are they?
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Old 19th January 2012, 10:27 PM   #23
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I measured D3 on the Voltage setting of 200. It measured 19.1. That seems low from the 24.9 it was supposed to read. Do I need a new D3 or what?
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Old 19th January 2012, 10:31 PM   #24
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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.
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Old 19th January 2012, 10:47 PM   #25
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So I put in another U5 from my other kit and it still doesn't work. Please help!
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Old 19th January 2012, 11:23 PM   #26
agdr is offline agdr  United States
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Quote:
Originally Posted by jschristian44 View Post
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.
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Old 19th January 2012, 11:30 PM   #27
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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!
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Old 19th January 2012, 11:36 PM   #28
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Also, there is no solder bridge at all on the U5. Plus I cannot test that because I can't get it to turn on! I am pretty sure it's a bad U5 shipment from Mouser. The other guy had the same thing and I tried 2 of mine which are bad. What can I do?
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Old 19th January 2012, 11:55 PM   #29
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Oh,
This part MC7809 says on the BOM that is for optional for AC only. Does this mean I need this part to run it only with the power supply and not batteries?
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Old 20th January 2012, 12:37 AM   #30
agdr is offline agdr  United States
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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.

Last edited by agdr; 20th January 2012 at 12:54 AM.
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