Bonzai CMOY.. Dead on One Channel - diyAudio
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Old 30th June 2012, 10:56 PM   #1
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Join Date: Jul 2004
Location: dresden
Default Bonzai CMOY.. Dead on One Channel

Greetings all,
I am not sure what is going wrong here but I will explain:

Built the CMOY and everything seemed to be working well. Of course I needed to get this into the case and somehow in my late night session which was two parts over training (cycling), and lack of sleep I put the opamp in backwards. Needless to say that didn't last long with smoke included...

New OPAMPS in now I get one side dead and other channel very very very low with just a hint of audible sound.
Checked caps one was dead so I changed them both just to be sure (matching).

Still a no go.
Doing power checks it seems one side with a battery work but the other nothing.

Ran through all resistors and they seem to be measuring correctly also.
I am pretty much at a loss here what is up but I suspect in power supply??
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Old 30th June 2012, 11:15 PM   #2
kumori is offline kumori  Europe
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Hey,

can you trace the voltage from the batterys along the powersupply to the op-amp pins?
Somewhere along the line you should see the fault, if it is the powersupply.
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Old 30th June 2012, 11:17 PM   #3
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Hey Kumori,
Still trying to do that.. Problem is the circuit board I did not build so its a bit more complex in unravelling the mystery.

Still at it though.
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Old 30th June 2012, 11:21 PM   #4
kumori is offline kumori  Europe
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So when you remove the op-amp, what voltage do you see at the powersupply-pins (pin 4 and 8, I guess)
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Old 1st July 2012, 12:52 PM   #5
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So measurements are:
with the one battery I am getting the LED working and on
pins 8 a voltage around 6 volts
pin 4 about the same -6volts

With two batteries its the same power reading however the second battery is placing power into the circuit as the cap is getting charged.
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Old 1st July 2012, 01:44 PM   #6
kumori is offline kumori  Europe
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Hallo,
is it one of these: ebay?

If I understand it right, with one battery, you get a positive and a negative voltage on the supply pins versus ground? I have no experience with this particular kit, but I would say, maybe you wired the battery wrongly.

If done right, the batteries are joint in the middle, this creates your 0V-reference. (as shown in the provided link) Than the free positive connector of the two batteries is connected to the positive supply pin. The same for negative connector and negative supply pin.

If you had wired it right, and connect only one battery, you should see only one supply voltage (positive or negative versus ground) at one of the pins. Can you check this?
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Old 1st July 2012, 02:31 PM   #7
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Battery is wired correctly and same with caps. In that regard it is pretty straight forwards so after 100 times checking its the same. No shorts on battery or caps either.

I am pretty much getting to the point on this and just tearing it apart and rebuilding on my own board.
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Old 1st July 2012, 02:42 PM   #8
kumori is offline kumori  Europe
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Ok, than I am also at the end my "knowledge".
But donīt give up yet, it is always the best kind of relief, when you find a really silly, simple and odd fault after several hours of looking :-)
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Old 1st July 2012, 03:12 PM   #9
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Pin 8 with one battery connected I get about 6+ volt.
Pin 4 is about -6ish range.

second battery alone
pin 8 about + 8 volts
pin 4 also about + 6????
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Old 1st July 2012, 03:51 PM   #10
kumori is offline kumori  Europe
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Join Date: Mar 2011
If your batterys are wired correctly, there are not many options what can go wrong because there are not many parts from the battery to the op amp.

If your opamp isn not yet taken out, take it out now.
I guess you can measure proper voltages at the battery contacts alone (the two contacts to form the center 0V should be joined and the other two contact schould be disconncted)

when you have the right voltages there, try to connect them individually. you schould see 9 volts (or -9 volts) at the supply pins. if not maybe the electrolytic cap for decoupling has a short. try to replace this one first before disassembling everything.
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