Sabotage Problem (answered)

[Anonymous]

Hello,

I’m having a problem with my Sabotage build.  The clean channel works fine, but no sound through the board.  Here are the transistor voltages:

 

Q1:  2.7  2.7  3.45

Q2: 4.3  3.0  9.2

Q3: 0  0  2.7

Q4: 0 0 3.2

Q5: 4.4  3.2  9.2

Q6: 4.1  0  9.2

 

Thanks in advance,

Paul.

 

 

[Anonymous]

Q1 is installed backwards.  The voltages measured are suspect.  The Drain voltages of Q2, Q4 and Q6 should all be the same as the supply voltage.  Q3 and Q4 are wrong.

After correcting Q1, remeasure and report all voltages.  Identify each as Q# D# B# S# or Q# E# B# C#.  This will help us further isolate the issue.

[Barry]

Q1 may or may not be backwards depending on the transistor being used.

If it is a BC550 then it is backwards.

If it is another type of transistor then it may need to be flipped as in the photo so we will need to know what transistor is being used in Q1.

That aside there are many readings that are off like Wilkie1 said.

[Anonymous]

You are correct, Barry.  SInce we did not hear otherwise, I had to assume that he used the same components specified in the Build Document.  Your document did warn that  other transistors may have a different pin out.

[Anonymous]

Sorry for the slow response, here are my numbers:  It’s acting a bit different today.I did put a cloth between the board and case to avoid any grounding problems.

Q1: 2N5485  D=2.697  G=3.442  S=2.702

Q2: MPSA18-J08 C=OL  E=OL  B=2.65 (Number kept moving but settled here)

Q3: MPSA18-J08 C=0  E=2.6 (Number kept moving)  B=0

Q4: MPSA18-J08 C=OL  E=OL  B=OL

Q5: MPSA18-J08  C=0  E=0L  B=0

Q6: MPSA18-J08  C=OL  E=OL  B=0

 

[Anonymous]

We definitely have an identify problem here.

You say you have a 2N5485 in Q1.  That is a FET that should be used in Q2 through Q6.  Q1 is supposed to be a NPN transistor BC550.

You say you are using MPSA18 in Q2 through Q6.  Those are NPN transistors. You need 2N5485 in Q2 through Q6.

Your voltages are all wrong.  You need to have about 9V on the drains of Q2, Q4 and Q6.

Correct the transistors and remeasure.  Be sure you are measuring correctly.  Consult our guides for more information.

[Barry]

OK so I deleted my first response since I was working from memory. That is what happens when you are busy packing after a new board release and throwing a Birthday Party.

I think we are mixing up transistor packs or something.

MPSA18 can be inserted in Q1 backwards if memory serves ???

Then as Wilkie points out the others Q2 etc. need to be JFETs.

[Anonymous]

Thanks!  I’ll see if I’ve got any of those floating around and report back.

[Author]

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