Sunking Tone Pot not working (and other issues)?

[Marcelo]

Hi all,
New to this forum. I just finished building the sunking and I am having some issues. First of all, the tone control appears to do nothing. rolling the pot does not have any effect in the sound. i looked at the board over and over and measured all components and everything seems to be ok. i am lost here. any idea where the problem could be (the pot works fine).
the other thing I noticed is that when I kick the switch on, i takes a little time for the pedal to kick in (a little delay with no sound). I am wondering if the two problems are related. any idea?? help!!!
thanks!
m

[jkokura]

It does sound like you have some issues doesn't it! Just so you're aware, you should NOT be having either of those issues.

First off, what I need you to do is hook up power to the board, and give us the following measurements using your Multi Meter's DC voltage setting. Put the black to ground and measure:

IC 1: Pins 1-8
IC2: Pins 1-8
IC3: Pins 1-8

Also, what will be very helpful is for you to describe whether you changed any part values, or if you modified the circuit at all. If you didn't that's fine, but sometimes you might think it's okay, but at other times you can't.

Just so you know, a very high percentage of the problems with builds are either a wrong or backwards part, a wiring mistake, or a poor soldering job. Check and then recheck all of those things, don't assume you did it right. I have installed a 100k resistor in place where it should have been 100 ohm because I wasn't aware there was a 100 ohm resistor! Check, and then recheck your part values, orientation, wiring, and soldering.

Also, if you post some good quality pictures of your build they may help us determine what you should do to get it running.

Hope that helps!

Jacob

[Marcelo]

Hey  jkokura, thanks for the reply. i know i screwed something up but i cannot find hte problem even after checking and rechecking over and over. maybe if you could get me a hint on where to look for the problem i can locate it. mods: i added a true bypass switch/wiring and i wired the led from the switch rather than using the board (could that be the problem? i cannot see it). here are the values i am getting on the ics using a battery (actualy measuring 8.36v):
ic1-1: 4.21v
ic1-8: 8.61v
ic2-1: 4.27v
ic2-8: 14.76v
ic3-1: 8.61v
ic3-8: 8.60v
i cannot upload pics due to file size. i'll try to reduce the resolution and upload them in a different post.
hope this helps. let me know if you have any hint. thanks!!!
m

[jkokura]

Hey man, you might have misunderstood what I meant.

when I posted IC 1: 1-8 it meant 1 'through' 8, not 1 'and' 8.

Those numbers look good so far, but they're aren't telling me anything about why your pedal isn't working. Good quality pictures will be very helpful.

Jacob

[Marcelo]

Ok got it. Here you go. i got some weird numbers... (some reverse polarity and some microv numbers). I still cannot upload pics due to size of fuiles but if ok with you I may be able to email them to you. let me know.
IC1:
1: 4.21v
2: 4.22v
3: 3.35v
4: 1.1mv
5: 8.33v
6: 4.16v
7: 4.16v
8: 4.15v

IC2:
1: 4.27v
2: 4.00v
3: 3.99v
4: -7.60v
5: 14.05v
6: 3.95v
7: 4.01v
8: 3.99v

IC3:
1: 8.61v
2: 4.14v
3: 2.1mv
4: -3.61v
5: 8.00v
6: 5.96v
7: 3.44v
8: -7.64v
thanks!
m

[madbean]

You've got the readings a little backwards there. The pins read 1-4 top to bottom on the left side and 8-5 top to bottom on right side. You've got the right side backwards.

Your overall supply voltage is a little low at 8.61 which leads me to believe that you've got a dying battery or a low rated PSU.

Ic2 pin4 should read closer to -9v, as should Ic3 pin5 (what you've labeled pin8).

Ic3 pin1 and pin8 (what you labeled pin5) should read +9v (supply voltage).

The intermediate voltages on Ic1 and Ic2 are more or less correct, although 1c2 pin8 (what you labeled pin5) is on the low side.


So, a low supply voltage could be part of the problem. Given the delay in sound when you click the bypass leads me to believe there is a faulty cap, perhaps.

Overall, I think there is a strong possibility of mis-wiring here. The best thing to do is to test the build independent of any switching or jacks on a breadboard. Time and time again, I try to emphasize this. Make sure that the effect works before wiring it to anything (except for the bare minimum of an input and output jack).

Anyway, not trying to single you out, but rather encourage you to try to make this part of your building process in the future.

As far as uploading photos, I believe I set the limit to either 500k or 1M per post, and you can upload pics via the "Additional Options" link at the bottom of the screen. Alternatively, you could upload them to Photobucket or something similar and link them here. I mention this because it might help us along a little further in diagnosing the problem.

[Marcelo]

Hey thanks for the reply and advise.
you are right on the pin labels. sorry. the left side are correct but 5 thru 8 are backwards. with respect to the drained battery, yes, but I only used for the readings. I tested the pedal with a power supply and fresh battery with same results.
what is your opinion regarding the tone pot not working? do you think it could also be a faulty capacitor? if so, i can try replacing caps one at the time.
I'll check the wiring again, in particular the tone pot ones.
re pics, the max size is 1000k, quite low for a good resolution pic. but thanks for the idea of posting a link. i'll upload some pics tomorrow and post a link.
thanks again and any further advise will be greatly appreciated!
m

[Marcelo]

Ok, I posted 2 pics of the pedal. Hope they show something that will lead me to the problem!

http://i1189.photobucket.com/albums/z427/mdcairo/IMG_1398.jpg
http://i1189.photobucket.com/albums/z427/mdcairo/IMG_1400.jpg

Healp Please!!!
m

[CRBMoA]

The first and biggest issue I see is the DC power jack not being insulated and sitting between the tone and volume pots.

[Marcelo]

DC power jack not being insulated and sitting between the tone and volume pots.

What is the reason this could be a problem? there is quite some room between the jack terminals/jack and the pots. are you thinking htey are almost in contact with each other?

[CRBMoA]

From the angle of your picture, it look slike the treminals of the DC jack may be making contact with the pot cases. If they are, you will have problems.

Where is C-3?

[jkokura]

True, Chris, but at the same time, if the DC jack was making contact he wouldn't get any sound whatsoever. If just the tone pot is not working right, then the problem is on the board with the tone stack. What's odd to me is that you've got fairly normal sound (I believe) except that the tone pot has no affect on the sound. That makes me think you've got either a crummy pot, bad wiring to the tone pot, or there's a problem in the board.

If you get out the schematic, locate all the parts around where the tone pot is, and begin to examine those parts on your board. Is on improperly soldered? Are any backwards? Are they all the right value? Reexamine the wiring. Get out a Multimeter and check that the pot is actually working.

jacob

[madbean]

Run a wire from the output to your guitar and test each lug on the tone pot.This is a quick and dirty audio probe.

[Marcelo]

I can see why you thought the DC jack may be in contact with the pots, but this is not the case. to make it clear, yes i get a nice sound out of the pedal, but the tone pot does not have any effect whatsoever. the other issue is a very small delay (no sound at all) when I push the switch on.
I went thru the entire board a couple of times, checking the orientation of the elec caps, ICs, etc. also I measured each component and compare it with the bill of materials.
I also checked the wiring and seems fine (with the exception of a different way of wiring the LED and the switch). I tested each pot with the multitester and seems since too.

Madbean, I am not sure I follow you on your proposed test, sorry, but would you mind expanding a bit more on what to do?

[CRBMoA]

OK - I believe you. I am just trying help.

  Where is C-3?