Boss OC-2 Harald Sabro Layout Help

[PeakyBlinders]

Salut Folks, i'm new here and first sorry my english is a bit rusty 
i have a problem with my Boss OC-2 Clone, i've build that from the Harald Sabro Layout,
https://www.sabrotone.com/wp-content/uploads/2011/10/BossOctaverOC2.gif

So far so good, Octave 1 and Direct Level works fine, but Octave 2 don't work, nothing happens when i rise up the pot
i also messured a few strange voltages, i checked the board double, on solder briges and wrong componets and for me it seems ok.
i'm helpless, can someone have a look on the measurements? and give me a tip where the problem possibly is located?

i've marked my measure findings which seemed strange to me in red, and the Sabro meassurements in brace green.




here is the Harald Sabro meassure chart, and the original Boss OC-2 schematic, pls scroll a bit down.
https://www.sabrotone.com/?p=1223

thanks a lot!
greetings Markus

[ElectricDruid]

Hi Markus, and welcome.

I took a look. I got a bit confused with the IC numbering, since Harald's list doesn't follow the schematic, but I got there in the end.

Firstly, I don't think the two odd results on IC3/LM324 are important. They are outputs that are supposed to switch either high or low, and yours seem to be doing that. You just happened to measure them while they were in a different state to Harald.

The IC5/4027 pin 3 result is a different story. That's supposed to be a CMOS logic output, so it should either be 9V or 0V (or close to those levels) and nothing like 4.69V - that's right in the middle!
That might happen if the connection between pin 13 and pin 3 wasn't actually connected (e.g. the input would not be connected - in the digital world that is called a "floating input", and it's generally bad!). That could be a missing wire link, or just a bad solder joint.

If you can sort that out, you might find that IC4/4013 starts to look more healthy. At the moment, I doubt it's getting a good input. Since it's generating the signals that control the second octave, if it isn't right, I'm not surprised you haven't got anything happening.

I hope that gets you started. Let us know what you find with the 4027.

[PeakyBlinders]

Hello Tom, actually i wouldn't do any stripboard cuircuit again, that has to do with modulation and that size, cause it's to error prone.
my knowledge on electronic is limited, but i like the challenge 
thank you so much, that's a good start for me to find the bug.

[PeakyBlinders]

hello again, i'm still try to debug this pedal. i changed all the IC's and transistors but the 2nd Octave Knob will not work.
there are some things i have figured out.
when i plug in the input cable, i meassure 9V on Pin 3, on IC5/4027, but if i hit the strings, then the Voltage goes down to 4,69 V something.

the second thing i've noticed was, if i meassure Pin 1 + 3 on the Octave 2 Potentiometer there is 0 Ohm,
my first thought was it is broken, but i meassured again without the cables, and then there was 100k Ohm.
i'm getting deperate, i try to fix this this pedal since 2 weeks with no result.
does someone have another advice?

i add some photos,
don't wonder i had bridged the Q2 to see if i get any Signal from Octave 2 and take away the TL072 to meassure the Pot.

[Slowpoke101]

A few silly questions;

1: What type of JFETs did you use for Q1 and Q2 ?
2: When you measured 0Ohms across the 2nd octave pot, was the pedal powered?
3: Got an audio probe?

Your construction and soldering skills are very good. I can not see any problems with the board except for one thing. There is a wire link under IC5 that connects to pin 5 of IC5. It looks like the wire pulled back from the solder joint and isn't making connection. Your voltage readings show that it is but double check anyway.

Also check the polarity of D6 and D7. Some germanium diodes are marked oppositely to what we expect.

[PeakyBlinders]

Thanks for your answer Ian,
i use 2SK30A JFET's for Q1+Q2
https://datasheet.octopart.com/2SK30A-Toshiba-datasheet-101654.pdf

i meassured 0 Ohm on Octave 2, if the Pot is wired and not powerd.
On Octave 1 and Direct Level i meassured 100k Ohm.

i did no audio probe, i have to figured out where to trace the audio signal for Octave 2
but the schematic confuse me.

The wire link to Pin 5 of IC5 is connected, i've checked this, and the polarity of the Diodes are in the proper direction, i've checked that, too

thank you for the flowers, but i'm not perfectly satisfied with my skills :-)

Edit: I've cleaned the stripboard traces once more, and now i've got a modulated Signal but very silent and distorted if i turn on the Octave 2 pot.
Octave 1 and Direct Level still Sound good.

[PeakyBlinders]

I've renew the wireing for the Octave 2 Pot again, and now i meassure 100k Ohm but there is still no Sound if i turn the Pot up.
Octave 1 and Direct Level are still fine.

I tried to trace the Signal and i noticed that the Signal on TL074 at Pin 8 = (Output 3), Pin9 = (Inverting Input 3) und Pin 10 = (Non-inverting Input 3

is very distorted

Pin 1-3 & 5-7 are fine

[Slowpoke101]

I've renew the wireing for the Octave 2 Pot again, and now i meassure 100k Ohm but there is still no Sound if i turn the Pot up.
Octave 1 and Direct Level are still fine.

I tried to trace the Signal and i noticed that the Signal on TL074 at Pin 8 = (Output 3), Pin9 = (Inverting Input 3) und Pin 10 = (Non-inverting Input 3

is very distorted

Pin 1-3 & 5-7 are fine

Good work with the Octave 2 pot. Finding wiring problems can be somewhat aggravating to say the least.
Now good work with chasing the signal, your result shows that some parts of the circuit are fine. A distorted signal at that point is normal.

After quite a bit or research I've come to the conclusion that this layout has a few little problems. Put everything back on the board (TL072, 2SK30A, etc ) and try the following;

C15 1uF Capacitor - Change it for a non-polarised type (film or MLCC ) or reverse the polarity of the one already there.
IC5 pins 6 and 7 - remove the small wire link between them and install a small wire link between pins 7 and 8.
Refer to the following picture;



Hopefully this will solve the problems.

[PeakyBlinders]

thank you very much for your help Ian, i really appreciated that.

I've did the changes you adviced me, and now I have a silent Signal if i turn up the Octave 2 Pot.
but it is very silent and distorted.
Octave 1 and Direct Level still work fine

thank you this bring me a big step forward.

EDIT: I Changed The TL072 and now i have on both Octave Signal, but Octave 2 is less strong in my opinion, and in general, i have a silent distorted signal in the background, till the strings stop vibrate. What could be the reason for that?

I will upload a sound exampe the next day's
till then, thank you to all for your support 

[Slowpoke101]

I did build this layout and had a bit of fun with it. The way Boss did the sub-octave effect is very clever and it does track surprisingly well. If anyone is interested, check out Merlin's (Valve Wizard ) U-Boat for a good explanation of Boss's technique and his very interesting alternative. By the way both Boss's and Merlin's methods leave the MXR (? ) Blue Box in the dust. Like the Blue Box octave effect playing technique is important - Neck pick-up, tone rolled down a bit (about mid-way ) and try to pluck the strings near the neck - this may be a bit difficult as some idiot has no doubt placed a pick-up right there.

This little octave effect can be fun. The first octave down can be heard without much difficulty. A little bit of it mixed with the dry signal really does make the guitar's sound more full - subjective analysis only as your results may vary. Octave 2 is of a far lower frequency and is getting near the lower end cut-off frequencies of everything (including our hearing ). Octave 2 is more felt than heard assuming the audio chain and amplifier can pass it (bass guitar amp stuff here )...Octave 2 is not very useful but can give a little bit more to the guitar signal - but you can barely (if at all ) hear it. An oscilloscope or a good audio spectrum analyser can show it better than most ears can experience it.

The Sabro layout works but do carry out the modifications that I have suggested in this thread as they do help. But I do have some other suggestions that I have tested. The first is to put the input buffer back in. Check out the circuit for the OC-2 on the hobby-hour website. You will need 2 x 10K resistors, 1 x 1M resistor, 1 x 22nF capacitor and a JFET (2SK30A or 2N5457 or a J201 ).

The second mod is to stop the interaction of the mix pots. See picture below;



Use a film capacitor for the 1uf. Polarity can be a pest and if you can dodge it, do so.

Please note that this picture does not include my recommended mod regarding the grounding of pin 7 of IC5. That mod was recommended as some 4027s don't always respond to an initial indeterminate set-up at power on. The output of pin 1 of IC5 may or may not change at all with the clocking input. The output can be indeterminate unless pin 7 is grounded.

The last mod is to calm the 4027 down a bit. One side of it is unused and left floating...CMOS chips don't really like this but most of the time they will not cause problems but it is best to prevent potential problems. Ground pins 10, 11 and 13 of IC5. Then connect pins 9 and 12 of IC5 to pin 16 (+9V ).

A fun effect. Try it.

[PeakyBlinders]

Hey Ian, thanks for the "Merlins" U Boat tip, i will give it a try.

I've a question in terms of the mods you suggest, what's the benefit to stop the interaction between the the mix Pots?, (i assume you mean the Octave Pots)
and can you clarify the buffer back mod, cause it's hard for me to read the schematic.

and third as i described the last time, i've have some very little silent distortion in my signal (see my sound examples) will the calm down mod solve the problem?
http://www.mediafire.com/file/x43vybb9v6br1m6/BossOC-2CloneSound_examples.zip/file

best regards, Markus