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Old 15th May 2007, 01:46 AM   #1
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Default A little XBOSOZ help

So I powered up PSU boards for xbosoz kit and measured +9 and 0 right before I started to see smoke!

I tried the second board same thing, not sure what to start checking to confirm PSU boards.

Before hooking up the boards I checked power supply was +70 and -28. Any suggestions would be great.

Thanks,
Pathmark
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Old 15th May 2007, 07:23 AM   #2
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Pathmark,
Could you provide a link to the schematic?

/Hugo
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Old 15th May 2007, 10:02 AM   #3
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The PSU was working properly by itself and then smoked when you connected the XBOSOZ, correct? I'll venture a guess that you got at least some of the 1000 uf caps in backwards on the XBOSOZ. You'll probably need to replace the caps.

That or you fried your fets (check for very high to infinite resistance Source to Drain in either direction. If not, they need replacing). Handle them carefully - a little static on the gate is all you need to fry them.
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Old 15th May 2007, 11:57 AM   #4
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Default More details

Sorry if not enough details. The boards are twisted pear audio based on Terry (metalman) schematic.

The xbosoz boards were not attached I was simply checking the PSU rails. Again on power-up the measured +9 and 0 (+ and - rails respectively) and then some smoke.

Pathmark
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Old 15th May 2007, 12:12 PM   #5
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I'd still guess a reversed cap somewhere or a solder bridge. Did you trim the component leads or could something have bent over and shorted.

I know where to find the schematic, but a link here would be handy.
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Old 15th May 2007, 01:13 PM   #6
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Default schematic info

Schematic for xbosoz psu
Attached Images
File Type: png xbosozschematicps.png (15.8 KB, 282 views)
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Old 16th May 2007, 12:47 AM   #7
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Pathmark-

Are you using two transformers?

I did not look up the Twisted pear wiring diagram, but the ps diagram you posted looks the same (as far as trafo wiring goes) as Nelson's original article.

When I first hooked up my BOSOZ ps, I tried to use a single transformer. I believe I had it wired wrong, which caused the magic smoke to quickly exit the bridges.

JJ
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Old 16th May 2007, 01:09 AM   #8
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Yes using two transformers for 30-0-30 for positive and 12-0-12 for negative, same avel as posted in forum.

I have posted on the xbosoz thread as it seems to have more replies. My issue is only with the positive rail on both boards! I only get 4.5V and then smoke.

Pathmark
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Old 16th May 2007, 01:18 AM   #9
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Check if zeners are put to the right direction.
Check the MOSFET's pins are correctly connected.


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Old 17th May 2007, 12:37 AM   #10
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Pathmark-

I would check those wimpy little 4004's to see if they are blown.

Also, if you have an unregulated power supply laying around, you can use it to check the regulated portion of the circuit past the diodes. A lower voltage PS, say +- 20 volts is better for this. (after doublechecking to see everything is installed correctly, of course.)
Just connect ground to ground, V+ to the junction between R1 and C1, and V- to the junction between R2 and C2. Your regulated voltage out will app. 3 to 4 volts less than your unregulated voltage.



JJ
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