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Meta42 trouble with rail splitter ...

post #1 of 8
1/27/11 at 12:07pm
Thread Starter 

I recently scored the board and chips plus some extra parts for a Meta42 on Ebay... couldn't resist since I got it for next to nothing. Thought this one might complement my other, much bigger headphone amplifiers :)

I was able to populate the board and build a matching Tread psu over Christmas and proceeded to check the important voltages. The psu puts out 24V (already cased up, center pin positive), but when I connect it to the Meta42 the input buffer immediately starts to heat up and I am having ~20V on pin1, about half on pin 2 and nothing on pin4 of the Elantec buffer. I rechecked all positions, replaced the TLE2426 once, reflowed all solder joints of splitter and buffer... no change.

My soldering skills usually are quite good and never made me trouble so far... but judge fo yourself.

 

http://s13.directupload.net/file/u/20659/skek3piz_jpg.htm

 

http://s13.directupload.net/file/u/20659/yby28l5y_jpg.htm

 

http://s1.directupload.net/file/u/20659/zyxcx48w_jpg.htm

 

 

I am out of ideas what might be wrong since even almost fully populated there are not many options to do something wrong... but I might be missing something redface.gif

 

I am thankful for any idea, hint, remark, comment...

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post #2 of 8
1/27/11 at 12:44pm

Do you have the power caps mounted the right way around?

The only other thing I can think of is blown EL2001.

 

Tangent would know best though...

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post #3 of 8
1/27/11 at 1:25pm

Are the inputs and outputs isolated from the chassis?

 

Is the wallwart in front of the Tread floating?

 

As an unrelated note: it looks like the right output has its solderpad lifted on the PCB in the last picture. Its near the middle/bottom edge of the third photo. 

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post #4 of 8
1/27/11 at 1:35pm

Looks like his power jack and RCAs might be shorted through the rear panel.

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post #5 of 8
1/27/11 at 5:06pm
Quote:
Originally Posted by Avro_Arrow View Post

Do you have the power caps mounted the right way around?


Good call. If the vents on those caps are always oriented w.r.t the leads the same way, at least one of those caps is oriented improperly. The "front" pair should be oriented the opposite way as the back pair, but if the vents are a clue, the frontmost one isn't oriented the same way as its neighbor, and it should be.

 

 

Quote:
Tangent would know best though...

 

 

Perhaps. Y'all seem to be doing pretty well. :)

 

Quote:
Originally Posted by nikongod View Post

Are the inputs and outputs isolated from the chassis?


I know the output jack: it's isolated.  (Plastic bushing.)

 

The inputs can be tied to the chassis, and that's a good idea.

 

But, as Avro points out, the power jack can't be tied to the chassis when you do that.  One or the other, not both.

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post #6 of 8
1/28/11 at 6:30am
Thread Starter 

 

Quote:
 

Do you have the power caps mounted the right way around?

 

     Quote:

 Good call. If the vents on those caps are always oriented w.r.t the leads the same way, at least one of those caps is oriented improperly. The "front" pair should be oriented the opposite way as the back pair, but if the vents are a clue, the frontmost one isn't oriented the same way as its neighbor, and it should be.

 Before I skinned them (those are Rubycon xxx) I made shure to have them oriented in pairs, so I do remember that I cut the leads on the bottom side in pairs either way... though the one vent out of orientation keeps bugging me. Still usually I am not that stupid to disregard proper orientation...

 

 

Quote:
 

Are the inputs and outputs isolated from the chassis?

 Inputs and outputs are isolated with plastic washers...

 

 

Quote:
 

Is the wallwart in front of the Tread floating?

 No wallwart in front of the Tread... I built the Tread with transformer, rectifiers, filtering and then Tread.

 

Quote:
 

As an unrelated note: it looks like the right output has its solderpad lifted on the PCB in the last picture. Its near the middle/bottom edge of the third photo. 

 

Like here...?

zyxcx48w.jpg

 

Must check when I get home... looks a bit suspicious.

But it wouldn't affect my problem...

 

 

Quote:
 

Looks like his power jack and RCAs might be shorted through the rear panel.

 

RCA's are isolated, but will doublecheck that insulation washers do not have contact somewhere accidentally---

 

Thanks everybody for your input so far!

 

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post #7 of 8
1/29/11 at 2:53am
Thread Starter 

 

Quote:
Looks like his power jack and RCAs might be shorted through the rear panel

Yeah, the winner is Avro Arrow...

As embarrassing as it is... for testing I forgot to mount the RCA's with the plastic washers...redface.gifredface.gif

After removing the RCA's from the back panel everything checks out fine... voltages exactly split

and the same on all important positions... glad that the splitter and buffer survived!

 

 

 

 

PS. No lifted solderpads whatsoever...

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post #8 of 8
1/29/11 at 9:22am

Good news for the solderpads. 

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