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Voltage drops of Placid HD after connecting load (BIII)
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niekos  
#21 Posted : Tuesday, January 1, 2013 7:12:31 PM(UTC)
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Originally Posted by: avr300 Go to Quoted Post
Now, hand over to Russ and Brian. I can't debug the AVCC shunt without schematic ;-)

Something is wrong with your AVCC shunt module.


Brian and/or Russ can you help me out? And a happy new year of course :)
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Russ White  
#22 Posted : Tuesday, January 1, 2013 7:54:15 PM(UTC)
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Check your solder joint's - in the pics they look dry.
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niekos  
#23 Posted : Tuesday, January 1, 2013 10:00:55 PM(UTC)
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I resoldered all joints, but it did not seem to make any difference so far.

SRA2 joints

new joints other side


I measured on the AVCC from the in/out/gnd joint to the first resistor/capacitor on the track and they were all ok.

I measured voltages again, the same as before (a bit higher):

On the side where SRA2 is printed in the board:

5,29V IN and 5,29 OUT

On the other side

5,29 in 2,4 V OUT.

I will resolder tomorrow once and measure all, just to be sure.


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Russ White  
#24 Posted : Tuesday, January 1, 2013 10:20:46 PM(UTC)
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please measure the voltage across D1, R4 and R5.
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niekos  
#25 Posted : Wednesday, January 2, 2013 7:02:28 AM(UTC)
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D1 = 0,98V
R4 = 3 mV
R5 = 283 mV
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Russ White  
#26 Posted : Wednesday, January 2, 2013 1:46:22 PM(UTC)
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Sounds like you probably have a dead transistor or two - and possible D1 too.

Your best bet unless you feel like replacing parts until you find the borked one is to order a replacement. :)
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niekos  
#27 Posted : Wednesday, January 2, 2013 3:18:06 PM(UTC)
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Thanks, what parts do you supect/advice to be replaced?
Do you have part numbers? I think it might be worth the try?
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Russ White  
#28 Posted : Wednesday, January 2, 2013 5:07:41 PM(UTC)
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Honestly - its probably more worth while to get the newer AVCC module anyway - it's a better circuit, but if you are intent on trying to fix it - I would say you might need to replace the following (in order of what to try first)

QP1-2 (BC856) (they are cheap so get a few extra in case QP3-4 are also dead)
D1 (once again order a few)

possibly the opamp (use OPA2209)
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thanks 1 user thanked Russ White for this useful post.
niekos on 1/2/2013(UTC)
avr300  
#29 Posted : Wednesday, January 2, 2013 6:19:56 PM(UTC)
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Originally Posted by: Russ White Go to Quoted Post
Honestly - its probably more worth while to get the newer AVCC module anyway - it's a better circuit,....


And it brings an increased sonic performance to the DAC. It's a very worthwhile upgrade.

(I'm not connected to TPA in any other way than being a satisfied customer).
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niekos  
#30 Posted : Wednesday, January 2, 2013 10:03:53 PM(UTC)
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ok ok, you convinced me :-) I just ordered a new one :-)
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