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OpAmp question - Nothing to do with stompboxes!

Started by jfrabat, July 07, 2020, 12:10:38 AM

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jfrabat

#20
July 09, 2020, 03:24:07 PM
Sorry, I grounded pin 7 in the last iteration by error.  Just corrected, but the problem is still there.

Corrected voltages:
Pin 1: 0V
Pin 2: 3.31V
Pin 3: 2.29V
Pin 4: 0V
Pin 5: 0V
Pin 6: 2.35V
Pin 7: 9.5V
Pin 8: 0V
I build.  I fix.  I fix again.  And again.  And yet again.  (sometimes again once more).  Then I have something that works! (Most of the time!).

antonis

#21
July 09, 2020, 03:33:19 PM
Short D1 & D2 to see what will happen..
(don't worry for crossover distortion for the moment..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

jfrabat

#22
July 09, 2020, 03:38:37 PM
Nothing...  I just used jumpers over the diodes.  Did I understand you correctly?
I build.  I fix.  I fix again.  And again.  And yet again.  (sometimes again once more).  Then I have something that works! (Most of the time!).

antonis

#23
July 09, 2020, 04:06:28 PM
Yeaapp.. Just to make sure for diode correct orientation..

edit: Just realized your +6V power supply.. :icon_redface:

Your measurements are correct so the only thing left is TR1/TR2 reverse placement..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

jfrabat

#24
July 09, 2020, 08:00:33 PM
Quote from: antonis on July 09, 2020, 04:06:28 PM
edit: Just realized your +6V power supply.. :icon_redface:

it is currently 9V, not 6V...
I build.  I fix.  I fix again.  And again.  And yet again.  (sometimes again once more).  Then I have something that works! (Most of the time!).

antonis

#25
July 10, 2020, 06:03:14 AM
In such a case, you MUST read 4.5V on both pins 2 & 3 (unless your DMM impedance is ridiculously low..)

Disconnect SPK1, short pin 6 with output capacitor left leg (or with D1 Cathode / D2 anode, if it's more convenient) and take measurements..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

jfrabat

#26
July 10, 2020, 05:04:01 PM Last Edit: July 10, 2020, 05:06:49 PM by jfrabat
Must have been a bad connection somewhere.  I plugged it in today and Pin 2 is 4.66V.  Tried it, and signal is going through.  However, it sounds lower in volume than the original (albeit with more gain - as in a bit distorted).  Gain knob does nothing, as far as volume goes, by the way.
I build.  I fix.  I fix again.  And again.  And yet again.  (sometimes again once more).  Then I have something that works! (Most of the time!).
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