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Old 30th January 2012, 03:59 PM   #1971
agdr is offline agdr  United States
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Quote:
Originally Posted by SEdwards View Post
The resistances seem to check out, but when I connect the AC U6 quickly becomes too hot to touch.
Remove the batteries, if there are any, turn the O2 power switch "off" (out), then plug the AC adaptor in and see if U6 is still heating up.

With the power switch "off" the O2 power supply is still on but not hooked to the mosfets and the rest of the amp. If U6 heats up with the power switch off you have a power supply short, otherwise the short is in the rest of the amp.
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Old 30th January 2012, 04:03 PM   #1972
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After a few plug and unplug, it should be ok.
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Old 30th January 2012, 04:52 PM   #1973
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Originally Posted by agdr View Post
Remove the batteries, if there are any, turn the O2 power switch "off" (out), then plug the AC adaptor in and see if U6 is still heating up.

With the power switch "off" the O2 power supply is still on but not hooked to the mosfets and the rest of the amp. If U6 heats up with the power switch off you have a power supply short, otherwise the short is in the rest of the amp.
Wow, thanks for the rapid tech support. The little guy is here mocking me.

U6 is heating up with the power switch in the 'off' position. Scolding hot, very quickly. I had a 'what the hell' moment and quickly plugged the cord in to measure V over the battery slots.

B1 gives 11.9 V, B2 gives 0, as far as I can tell. I didn't want to leave the plug in long.

Need to run to pick up dinner, but will be watching keenly for things to try.

P.S. Adapter is one I found in my dad's shed. From a light I think. I can write down the specs shortly.
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Old 30th January 2012, 05:36 PM   #1974
agdr is offline agdr  United States
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Quote:
Originally Posted by SEdwards View Post
P.S. Adapter is one I found in my dad's shed. From a light I think. I can write down the specs shortly.
Yeah, that is the first most important thing. Needs to have AC output, not DC like most adaptors.

If the adaptor is OK and in the range of 12VAC - 20VAC then work through the steps I posted starting with post #1855 in this thread. That was for a fellow having the same issue as you but with a dead positive supply instead of the dead negative. For the negative supply you would look at D4, C3, C5, U6, C7, D5 and R2 instead.

Also read through this thread helping another fellow debug an O2 power supply. A boatload of good troubleshooting info in there.

My Objective 2 Will Not Turn On

Last edited by agdr; 30th January 2012 at 05:48 PM.
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Old 30th January 2012, 05:44 PM   #1975
sonja is offline sonja  Norway
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I need a power adapter for the objective2, which is capable of 230V environment. It was a link to an ebay site some time ago, but I don`t remember where I saw it. I think it was on the ebay UK. Anybody knows?
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Old 30th January 2012, 05:57 PM   #1976
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Originally Posted by agdr View Post
Yeah, that is the first most important thing. Needs to have AC output, not DC like most adaptors.

If the adaptor is OK and in the range of 12VAC - 20VAC then work through the steps I posted starting with post #1855 in this thread. That was for a fellow having the same issue as you but with a dead positive supply instead of the dead negative. For the negative supply you would look at D4, C3, C5, U6, C7, D5 and R2 instead.

Also read through this thread helping another fellow debug an O2 power supply. A boatload of good troubleshooting info in there.

My Objective 2 Will Not Turn On
Thanks for the links. The supply is
Input: 230-240V-50HZ
Output: 12V Max 12VA

So it is AC. It gives only 12.8 VA, though, so I know I need a better one. I thought I could use it to test the circuit. I'm looking intently for shorts but can't find one at the moment. Maybe I just killed U6.

If I link to some pics would you be willing to be critical of my joints?
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Old 30th January 2012, 06:04 PM   #1977
agdr is offline agdr  United States
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Quote:
Originally Posted by SEdwards View Post
Thanks for the links. The supply is
Input: 230-240V-50HZ
Output: 12V Max 12VA

So it is AC. It gives only 12.8 VA, though, so I know I need a better one. I thought I could use it to test the circuit. I'm looking intently for shorts but can't find one at the moment. Maybe I just killed U6.

If I link to some pics would you be willing to be critical of my joints?
Unfortunately solder bridges wouldn't show up well in a photo. Best thing to do is use a magnifying glass and take a look at them directly. Especially the solder joints on U6 - it is very hard to see a bridge between those pins without the magnifier.

You should get -24.9V or so to ground (metal shell of the gain switch) at the non-banded side of D4, going into the regulator.

Last edited by agdr; 30th January 2012 at 06:07 PM.
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Old 30th January 2012, 06:46 PM   #1978
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Whoops - make that -19Vdc with a 12VAC adaptor.
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Old 30th January 2012, 07:18 PM   #1979
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I guess the case didn't come with rubber feet?

I'll have to get a set of 4.
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Old 30th January 2012, 08:16 PM   #1980
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The case doesn't come with feet which is a shame because it slides around everywhere!
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