SOLVED Parenthesis octave problem

[K Pedals]

I just finished the new board and everything works good except when I turn the octave on...When I engage the octave switch the more I turn the potentiometer up the less volume the distortion has... like it’s sending it to ground and there is no octave at all...
Do you see any obvious mistakes on the board/wiring???

 

[JetFixxxer]

Wow...
Lol
I feel dumb...
Thank you for the help!!!!

We've all bee there.

Checked my resistor and all the values are correct. What's the voltage suppose to be at Q4?

 

[Chuck D. Bones]

Q4 collector should be around 6.5 to 7V. Q2 emitter should be around 4V.

 

[JetFixxxer]

Q4 collector should be around 6.5 to 7V. Q2 emitter should be around 4V.

I'm getting 8.6

 

[Chuck D. Bones]

On Q2? Something's not right there. Measure the voltage on Q2 E and Q2 B. Let's see if the transistor is bad or the bias resistors are wrong.

 

[JetFixxxer]

On Q2? Something's not right there. Measure the voltage on Q2 E and Q2 B. Let's see if the transistor is bad or the bias resistors are wrong.

No I got that on Q4.

 

[Chuck D. Bones]

Sorry, typo on my part. Please measure the emitter & base voltages on Q4. Are you using a battery or a 9V power supply?

 

[JetFixxxer]

Power Supply...

C= .9v
E= 8.5mV

 

[Chuck D. Bones]

Before, you said C = 8.6V.

 

[JetFixxxer]

Before, you said C = 8.6V.

My typo...
I have two DMM here at the house and they both are coming up with the same values.
C= 8.6v
B= 88.5mV
E= .1mV shows for about a few seconds, then drops for .00.

 

[Chuck D. Bones]

Something is wrong with R18 or R19. Q4's base should be around 800mV and the emitter around 150 to 200mV. Make sure R18 is 47K and not 4.7K. You can actually measure R18 in-circuit. With the power off, measure the resistance across R18 first one way, then reverse the leads and try the other way. Wait for the meter reading to settle. The higher reading is closest to reality. It won't be super accurate, but will tell us if R18 is in the ballpark or not.

 

[JetFixxxer]

Something is wrong with R18 or R19. Q4's base should be around 800mV and the emitter around 150 to 200mV. Make sure R18 is 47K and not 4.7K. You can actually measure R18 in-circuit. With the power off, measure the resistance across R18 first one way, then reverse the leads and try the other way. Wait for the meter reading to settle. The higher reading is closest to reality. It won't be super accurate, but will tell us if R18 is in the ballpark or not.

That's it! Will change it out tomorrow and let you know.

4.7k resistor instead of 47k.. I feel like an ass (wasting peoples time) I checked last night after PedalPCB posted this fix. Not sure when I was verifying the resistor colors that I used part of R18 and the last 2 band of R16.

 

[K Pedals]

That's it! Will change it out tomorrow and let you know.

4.7k resistor instead of 47k.. I feel like an ass (wasting peoples time) I checked last night after PedalPCB posted this fix. Not sure when I was verifying the resistor colors that I used part of R18 and the last 2 band of R16.

Glad you figured it out!!!
That’s weird we both made the same mistake...

 

[JetFixxxer]

Glad you figured it out!!!
That’s weird we both made the same mistake...

Unfortunately I didn't figure it out. I have thank Chuck, Pedal, and all the others for that.

I went through the schematic several times and even after thinking R18 could be the culprit. Then once again when once the fix for yours was posted. It still didn't register that I had a 4.7k in there instead of a 47k. Not sure why I thought I was a 47k each time I went through verifying.

 

[tmiso]

I’m having a very similar problem with mine. Volume drop when engaging the octave switch and turning the octave knob up. I’m also getting a volume drop when turning the filter pot up. Functions fine when both the octave and filter are rolled back all the way. Was this what was happening with your as well or was it just the octave pot that made it go quite?

 

[JetFixxxer]

Works great when the correct value R18 resistor is installed.

 

[Thunderstruckmjh]

Hey all,

So I have been having this exact issue. I discovered R18 was incorrect on mine too. Went ahead and fixed that, but I'm STILL not getting the octave to work. I went through each resistor and checked values (by the color coding, not a guarantee it's correct, but I like my chances.) I noticed in previous comments that Q2s emitter should be around 4V. I'm down to ~20mV. Something sure ain't stirring the kool-aid here.

Really scratching my head. Could someone kindly measure all the Q voltages in the octave section and post them?

 

[tommasoc]

On Q4 collector i have 6,74v, but on Q2 I have this situation:
Emitter 4,50v
Base 4,78v
Collector 10,5v

I checked R18 but on my board I have the correct value, se the picture.
Any suggestion? I still don't get it

 

[Nostradoomus]

Can you take more pictures? Try to get the whole board and the underside too.

 

[Chuck D. Bones]

On Q4 collector i have 6,74v, but on Q2 I have this situation:
Emitter 4,50v
Base 4,78v
Collector 10,5v

I checked R18 but on my board I have the correct value, see the picture.
Any suggestion? I still don't get it

Q2 and Q4 voltages look good. Q2-B reads low because your meter is loading it down. You must be using an unregulated power supply to power this thing because Q2-C = Vcc = 10.5V. It should still work at that voltage. Based on your measurements, Q3-E should be about 7.4V; Q3-C should be about 3.1V. Please verify.

For fun, drill a 3mm hole in the front panel behind D6, then mount D6 on the other side of the board, looking thru the front panel. When the toggle sw is in the ASYM position, the LED will glow when you play.

 

[Chuck D. Bones]

Hey all,

So I have been having this exact issue. I discovered R18 was incorrect on mine too. Went ahead and fixed that, but I'm STILL not getting the octave to work. I went through each resistor and checked values (by the color coding, not a guarantee it's correct, but I like my chances.) I noticed in previous comments that Q2s emitter should be around 4V. I'm down to ~20mV. Something sure ain't stirring the kool-aid here.

Really scratching my head. Could someone kindly measure all the Q voltages in the octave section and post them?

Verify you have 4.5V on D2 & D3 cathodes. If that's good then either your diodes are not leaky enough, Q2-B is shorted to ground or Q2 is dead. How about posting a picture?