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igy137  
#1 Posted : Tuesday, October 9, 2012 7:39:49 AM(UTC)
igy137

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Hi All,

I just finished assembling a Placid HD, and set the VR1&2 according to the manual.
All looked good, so adjusted VR2 until I got 5.25V on output, which seems to be fine & stable.

At this point I measured voltage between test points:
TP_OUT+ and TP_SHUNT+ = -23mV
VIN+ TP_CCS+ = -25mV

Is it ok to measure negative values here?
At this point I have no load attached, I wanted to make sure everything is ok before continuing.

(Note: on the Placid HD BP I see the same, and on the negative side I see positive values between the above test points.)

Thanks,

igy
Russ White  
#2 Posted : Wednesday, October 10, 2012 2:41:40 AM(UTC)
Russ White

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The polarity of the value will depend entirely on which probe is where. :)
igy137  
#3 Posted : Wednesday, October 10, 2012 9:49:59 PM(UTC)
igy137

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Thanks Russ, I guess this means, it's ok :)

Actually I moved forward and connected it to the Buffalo III. It was able to nicely lock to my I2S source, pretty cool :)
CCS is around (-)500mV, shunt is around (-)50mV :)

After a few minutes the initial 5.25V drops 0.12V, as expected based on the manual.
However, I noticed that transistor QN1 gets much warmer than QN2 (comparing the heatsinks). While the QN2 gets warm, but no problem to touch, QN1 feels much warmer for sure, can hold my fingers only for a few secs on it.

Is this difference normal?

igy
Russ White  
#4 Posted : Wednesday, October 10, 2012 11:48:54 PM(UTC)
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It is perfectly fine for one heatsink to be warmer than the other. The difference will be purely dependant on the situation.
igy137  
#5 Posted : Thursday, October 11, 2012 5:26:09 AM(UTC)
igy137

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Thanks!
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