BYOC Optical Compressor- issue?

[g1]

Can you recheck pin 2 ?
For others reading, my interpretation of the layout is that pin 2 belongs to IC1B on schematic (lower op amp).

Anyone else care to comment on pin2 reading 0 volts?

[J M Fahey]

1) the schematic is *orrible* (sic) .
Who's the braindead designer?
Why does he use the same number for different points?
To boot, 3 or 4 times?
No, I couldn't care less they are different colours.

2) this is the 4558 pinout, referring to the IC pins themselves, ignore the goofy schematic:




in each Op Amp, the non inverting + input sets the reference, the output does whatever it can (which implies some times it can not) to keep the inverting - input at same voltage as + input or at most a couple millivolts away.

so back to the posted values:
Pin 1. 4V <-good
Pin 2. 0V <-wrong
Pin 3. 4V <-good
Pin 4. 0V <-good

Pin 5. 2.7V <-wrong
Pin 6. 4V <-good
Pin 7. 4V <-good
Pin 8. 8.5V <-good

given that the output voltages are right, which would be an incredible coincidence, I suspect poor measuring, please recheck.

Edit:
* and the Opto LED is drawn backwards.
* and the gain/compression pot must be an anti log / "C" type ; a Lin "B" one will have 90% of the effect in the last 10% of its setting.
* no, you can't correct that with a resistor in parallel with the cursor.

Personally, I'd use a small rotative switch and select between 560k/220k/75k/27k/10k which is a very smooth progression with the right curve.

[nickb]

Pin 1. 4V
Pin 2. 0V
Pin 3. 4V
Pin 4. 0V

Pin 5. 2.7V
Pin 6. 4V
Pin 7. 4V
Pin 8. 8.5V

Let's add some pin numbers to the schematic:

[Mick Bailey]

There are two versions of the pedal according to the BYOC schematic archive, though I didn't see any revision notes;

Instruction Archive ? Build Your Own Clone

[nickb]

There are two versions of the pedal according to the BYOC schematic archive, though I didn't see any revision notes;

Instruction Archive ? Build Your Own Clone

As far as I can see the circuit is the same but I felt the annotation present on the rev 1 sch would be helpful to the discussion.

You need to sort out the odd measurement results but, if it's basically working and the attack time constant is too short and from your description it's underdamped , then I'd hazard a guess that the 33uF cap C6 is open.

[Sea Chief]

Hi chaps- great help and info, appreciated.

Re-measured Pin 2. is 4V (not 0V). Apologies.

All other Pins re-measured/ as above. Pin 5 -is- 2.74V

The 33uf caps are securely in place/ all legs continuity to next spot ok.

[Sea Chief]

There are two versions of the pedal according to the BYOC schematic archive, though I didn't see any revision notes;

Instruction Archive ? Build Your Own Clone

Yes 2 versions. This is simply version 1.

[nickb]

Hi chaps- great help and info, appreciated.

Re-measured Pin 2. is 4V (not 0V). Apologies.

All other Pins re-measured/ as above. Pin 5 -is- 2.74V

The 33uf caps are securely in place/ all legs continuity to next spot ok.

Pin 5 could be due to meter loading - what is the make the & model of your meter?

"Open" includes problems internal to C6 as well. Try one in parallel.

[Sea Chief]

Pin 5 could be due to meter loading - what is the make the & model of your meter?

"Open" includes problems internal to C6 as well. Try one in parallel.

You mean swap out C6 for another? I have only a 22uf and a 10uf.. can you remind me whether Im connecting these 2 in series or parralel to get 33uf (www info is stupidly complicated for such a simple answer it seems). thanks

[J M Fahey]

Hi chaps- great help and info, appreciated.

Re-measured Pin 2. is 4V (not 0V). Apologies.

All other Pins re-measured/ as above. Pin 5 -is- 2.74V

The 33uf caps are securely in place/ all legs continuity to next spot ok.

Ok, the pin 5 is real 4V ... but the meter internal impedance which I guess is 1M is pulling that voltage down while measuring.
Same thing as adding a 1M resistor from pin 5 to ground; couple that with the reference 4V (~1/2 Vcc of 8.5V) coming through a 470k resistor and you understand the voltage drop.
And how am I so certain there's 4V there if I don't trust the measurement?
Because I have 4V on pin 7 that is , and the Op Amp works like a very high impedance, unity gain (at DC) buffer .
Measurement is correct at the other Op Amp on pin 3 , because it comes straight from the voltage reference point.

Ok, back to the BYOC, now I'm certain the Op Amp is fine but we still have a functional problem.

Since we seem to have a time constant problem, I'd pull suspect C6, solder 2 pieces of solid wire (clipped resistor leads are fine) where it used to be, to avoid overheating the PCB pads, and solder to them different caps.
Try 1/10/100 uF and check which one you like best.
Too small: very fast tracking but may distort or show some kind of Tremolo effect (the compressor trying to track even the smallest signal variations real time) .
Too large: the compressor will duck too much and take forever to recover signal level, similar to what camera and You Tube built in compressors do.

** verify the Opto LED is wired the proper way, the schematic is WRONG **

*maybe* the layout is right anyway, sometimes happens either by chance .... or on purpose ..... a homemade build (following just the bare schematic) does not work but the "official" kit or at least the "official" PCB does

Thanks to nickb , I'll further edit his editing by killing the silly confusing reference numbers (which I guess refer to pads on the "official" PCB, confusing those which don't use it) and correcting LED(s) orientation:

[Sea Chief]

Ok, the pin 5 is real 4V ... but the meter internal impedance which I guess is 1M is pulling that voltage down while measuring.
Same thing as adding a 1M resistor from pin 5 to ground; couple that with the reference 4V (~1/2 Vcc of 8.5V) coming through a 470k resistor and you understand the voltage drop.
And how am I so certain there's 4V there if I don't trust the measurement?
Because I have 4V on pin 7 that is , and the Op Amp works like a very high impedance, unity gain (at DC) buffer .
Measurement is correct at the other Op Amp on pin 3 , because it comes straight from the voltage reference point.

Ok, back to the BYOC, now I'm certain the Op Amp is fine but we still have a functional problem.

Since we seem to have a time constant problem, I'd pull suspect C6, solder 2 pieces of solid wire (clipped resistor leads are fine) where it used to be, to avoid overheating the PCB pads, and solder to them different caps.
Try 1/10/100 uF and check which one you like best.
Too small: very fast tracking but may distort or show some kind of Tremolo effect (the compressor trying to track even the smallest signal variations real time) .
Too large: the compressor will duck too much and take forever to recover signal level, similar to what camera and You Tube built in compressors do.

** verify the Opto LED is wired the proper way, the schematic is WRONG **

*maybe* the layout is right anyway, sometimes happens either by chance .... or on purpose ..... a homemade build (following just the bare schematic) does not work but the "official" kit or at least the "official" PCB does

Thanks to nickb , I'll further edit his editing by killing the silly confusing reference numbers (which I guess refer to pads on the "official" PCB, confusing those which don't use it) and correcting LED(s) orientation:
[ATTACH=CONFIG]34610[/ATTACH]

Ive just removed C6 but such are the minute tracks and the tricky removing of it, both tracks were lifting. Ok I tried to spot-solder a link between the 2 (3mm apart) buts its just impossible its too small & Im just further damaging the tracks.

Ok so I tried to just solder C6 back in as gently as posssible, but not successful- the pedal doesnt work at all now. F88k it.

[Sea Chief]

Chaps I think Im done with this f**king thing. The board & tracks are so small my fat fingers just cant deal with even removing X it seems, & even if found the prob to Y Id need to take it to a tech. It makes me hate pedals with even more vengence than I did before. One chorus pedal- thats it for me (I built- and it sounds great).

[Rant edited for cnuts f&cks and one c*ck. Tracks rescued I think so C6 back ok I think].

Thanks for your help tho. SC

[Mick Bailey]

Are you in the UK?

If so I'll fix it for free for the price of return postage.

[nickb]

Are you in the UK?

If so I'll fix it for free for the price of return postage.

I think you're up North Mick? What a nice guy!

SC: if you're in the SW call by and we can do it together. I can't bear to see a grown man weep

[Sea Chief]

Are you in the UK?

If so I'll fix it for free for the price of return postage.

Guys thanks so much. NickB Im south midlands but thank you. Im going to undo my rant now after clearing my head.

Mick I gladly accept- a gentleman you are. I do hope there is a prob & its not a case of 'thats how they are, you muppet' but I guess youd know straight off w'out wasting any time if so. Im fairly damn sure its not meant to be like this tho, but, what with gtr > amp stuff such a stalwart mystery to me.. there is a chance it could be exactly how theyre meant to be. I have done a decent salvage job on the tracks & C6 is back ok/ works as it did at least.

Thanks SC.