I built a Tread and a Pimeta...then...big oops!
Jul 14, 2005 at 2:05 AM Thread Starter Post #1 of 11

WSikorski

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I need some advice from the group.

Tested the Tread - OK.
Tested the Pimeta on batt power - OK.
Tested the Pimeta / Tread combo - OK.

The pimeta has been set as class A using:

Tangents Pimeta board v1.1b
AD8620AR, AD8610AR op amps, Burr-Brown BUF634 buffers ,Wima MKS-2, ELNA Cerafine, BC2062-ND Caps ,ALPS RK27, Pimeta cascode set, Vishay Dale resistors and silver-bearing solder.

Now the horror story...

Everything worked better than expected, adjusted the Tread to 24v, hooked it up to the Pimeta, it sounded great. My first "electronic" project in about 10 years.

The horror part of the story?

The Pimeta and Tread were/are sitting on top of the cigar box that I used for a work surface. I haven't gotten to the point of installing in a case yet. I figured that I should test every thing first.

While listening to some Acoustic Alchemy, I called my wife in to listen to my new toy and the left side output on the 1/8" jack fell against the LED on the Tread. Loud buzz, left side output all but non-existant. Left side buffer heated up, it's toast. No spares on hand. Right side still sounds good.

Is it possible that I also ate the left side of the op amp? I am going to need to order up some replacement parts.

So far, Buffer and AD8620AR.

What else might have fried? The left buffer was the only "hot" component.

Thanks for any help/advice.

Wayne

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Jul 14, 2005 at 3:18 AM Post #3 of 11

WSikorski

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Quote:

Originally Posted by James281
do you mind post up the picture again? bigger! thanks.
http://photobucket.com/

sorry to hear about your oops
wink.gif
how about try to the the good side buffer and put on the bad side to see if it going to work or not..



If I switch the Left and right buffers, the right side gets quiet and the left is louder, but distorted. Switch back, right side fine, left side quiet.

I think the Op Amp toasted also, at least the left side.

Wayne

Edited to show better picture and dump attachment.
 
Jul 14, 2005 at 4:03 AM Post #4 of 11

Jazper

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Quote:

Originally Posted by WSikorski
If I switch the Left and right buffers, the right side gets quiet and the left is louder, but distorted. Switch back, right side fine, left side quiet.

I think the Op Amp toasted also, at least the left side.

Wayne

Edited to show better picture and dump attachment.




Your logic sounds reasonable.

you may need to change the bias transistors also

EDIT: please tell me you're not running the tread without a heatsink on the LM317 - !!
if possible use isolators so the heatsink isn't electrically connected to the back of the chip
 
Jul 14, 2005 at 9:17 AM Post #6 of 11

mono

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Quote:

Originally Posted by Jazper
please tell me you're not running the tread without a heatsink on the LM317 - !!


Depending on Pimeta config and initial transformer voltage, there is no need for a 'sink on it. Suppose the amp draws around 70mA in that config. Suppose input voltage is from a (now lightly loaded) 24V transformer rectified down to around 32V, with regulated output 24V. That's only 1/2 watt heat.
 
Jul 14, 2005 at 8:08 PM Post #8 of 11

WSikorski

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Quote:

Originally Posted by Jazper
Your logic sounds reasonable.

you may need to change the bias transistors also

EDIT: please tell me you're not running the tread without a heatsink on the LM317 - !!
if possible use isolators so the heatsink isn't electrically connected to the back of the chip



Thought that might also be a problem, ordered.

I have a heatsink with mica isolator and plastic bushing. It barely warmed up in the ten minutes that it was running.
 
Jul 14, 2005 at 8:11 PM Post #9 of 11

WSikorski

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Quote:

Originally Posted by JackH
I may not be seeing this correctly, but is that a capacitor where the LED is supposed to go (pimeta board, between the pot and c4+)?


Nope, just the temp position for the blue LED. Sure does look like a cap in the pic though.
 
Jul 15, 2005 at 3:02 AM Post #10 of 11

Jazper

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Quote:

Originally Posted by WSikorski
Thought that might also be a problem, ordered.

I have a heatsink with mica isolator and plastic bushing. It barely warmed up in the ten minutes that it was running.




cheap insurance imho - general rule is if it gets warm, and you can, stick a heatsink on it
 
Jul 16, 2005 at 11:48 PM Post #11 of 11

WSikorski

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UPDATE on the minor disaster...

It turned out that I only fried the the left output buffer on the amp.

Unfortunately I killed the left side of my Senn PX 200's.

Oh well, This time testing with cheapie ear buds. Now I just need to pick a case.

Thank you all, for your input.

Wayne
 

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