Blackfinger Compressor - low output

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Blackfinger Compressor - low output

sonicsunspot
Background:  this is my 5th DIY pedal build.  First using Vero Board.  Appreciate any help I can get and your patience.  Something appears to fundamentally wrong with my build, negative values (is this normal in any build ever?) in IC and transistor voltages.  I am using the Mirosol Test Box with Input, Output, Ground and Voltage hooked up to a fresh 9V for the measurements below.  I feel really stupid NOT knowing if the negative voltages are normal and my gut is they ARE NOT and this is the basis for my problem.

- verified all cuts with Fluke and all appear clean (not continuity between strip cuts)
- verified all jumpers and all appear to have continuity
- verified all resistors for accuracy - appear good
- swapped ICs just in case one was bad
- used audio probe to trace some of the input circuit - because I am a novice I am not quite sure about the results, but I can hear places where the signal really drops.

Problem:  Very, very low output.  Have to crank volume to max and pluck strings hard to hear anything.  Effects seem to be working.

This is my first real attempt to use the debugging board here, I am trying hard to follow the directions as posted in "Read this before posting".

Layout:  http://tagboardeffects.blogspot.com/search?q=black+finger

Transistor voltages
Q1
C = - 8
B = - .9
E = - .4

Q2
C = 9.0
B = 0
E = - .1

Q3
C = -9
B = 0
E = -.7

Q4
C = 9
B = .4
E = .4

Q5
C = 5.5
B = 5
E = 5.5

Q6
C = -9
B = .1
E = .7

IC Pin Voltages
IC2
1 = -8.68
2 = -.072
3 = -.062
4 = -8.63
5 = -8.61
6 = -.041
7 = 8.69
8 = 0

7660s
1 = 8.66
2 = 5.06
3 = 0
4 = -3.6
5 = -8.61
6 = 3.7
7 = 5.2
8 = 8.66

CA3080
1 = 0
2 = 0
3 = -.01
4 = -8.64
5 = -8.00
6 = .07
7 = 8.66
8 = 0





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Re: Blackfinger Compressor - low output

PMowdes

I'm not super familiar with this one but the schematic seems to suggest that it is bipolar 9V, the original used two 9v batteries, i assume one is +9v and the other -9v



If you are debugging it is ALWAYS a good idea to try to track down a schematic.  you can have a look to see where you need to have specific voltages and you can track the audio through the circuit / vero.  if you have an audio probe you can use the schematic to track the audio as well.

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Re: Blackfinger Compressor - low output

nostradoomus
In reply to this post by sonicsunspot
Is that not perfboard?
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Re: Blackfinger Compressor - low output

PMowdes
In reply to this post by PMowdes

Also what is the chip that isn't a ca3080????
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Re: Blackfinger Compressor - low output

sonicsunspot
Thanks for the fast response!

PMowdes - chip is a NTE996.  I could not find CA3080s anywhere, found this used as a substitute.