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PostPosted: Sat Nov 19, 2022 11:50 am 
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I tried out this octave up module for my crown jewel. Seemed liked a pretty straight-forward build. It seems way too quiet though. I have to crank the boost channel volume all the way up, and it's still quieter than bypass. Same thing if I also have the drive channel on, the boost circuit is sucking the volume out.

I also don't think it sounds like it should. It does have an effect on the tone, but doesn't sound like I'm getting any "octave up" effect.

I already reflowed all the joints, to no effect.

The only part I'm not quite sure about is the diodes. The instructions say "if they have a gray stripe and a white stripe, gray goes to square hole". But the diodes I got don't look like that. One end has two black stripes, so I figured those went to the square hole.

Any idea if these are the right diodes, and if the orientation is correct?

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PostPosted: Sat Nov 19, 2022 12:45 pm 
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Two things:

  • Are you sure that you have the two 3904 transistors and the one 3906 in the correct positions?
  • The resistor I've circled below appears to be a 1.8K, while the PCB silkscreen and the circuit schematic both indicate an 18K. Since that resistor is part of the voltage biasing for one of the 3904's, it could be causing your problem if I'm reading the color code right. Try reading the resistance with your multimeter--it may come out a bit low since it's in the circuit, but it should be close to 18K if it's the right one.

The diodes look OK to me.

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octup_resistor.jpg
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PostPosted: Sat Nov 19, 2022 1:17 pm 
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Joined: Tue Feb 02, 2021 7:32 pm
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duhvoodooman wrote:
Two things:

  • Are you sure that you have the two 3904 transistors and the one 3906 in the correct positions?
  • The resistor I've circled below appears to be a 1.8K, while the PCB silkscreen and the circuit schematic both indicate an 18K. Since that resistor is part of the voltage biasing for one of the 3904's, it could be causing your problem if I'm reading the color code right. Try reading the resistance with your multimeter--it may come out a bit low since it's in the circuit, but it should be close to 18K if it's the right one.

The diodes look OK to me.

Attachment:
octup_resistor.jpg
Yeah the transistors are in the right place. Looking at the resistor color bands, I would agree it does look more like a 1.8 k(that 4th band looks more brown than red) - but I've triple checked it with my digital multimeter, and it unambiguously reads 18k.

I found an old threads asking a similar question about diode position. Looking closely at my diodes, I wasn't convinced either way, but just out of curiosity I went ahead and flipped them around.. and I would say it works better now. The volume is roughly the same as bypass now, and I think I get more of that green ringer sound.

So I think I'll consider this resolved.

Thanks for looking, as always, @duhvoodooman !

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PostPosted: Sat Nov 19, 2022 4:09 pm 
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They looked right to me, but if it works, it works! Those Russian germaniums are confusing! In any case, enjoy! :mrgreen:

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