Pork Barrel (VER 4) LFO Not working

[kryoz]

Hi everybody... my name is Hernan and i am from Argentina..

I am really sorry that my first post here is about asking for help but i really have no clue of what is going on with my pork barrel build.. I´ve been reading FSB and DIYSB and building a couple of projects for the last years.

I´ve etched a previous version of the pork barrel (the one with all the tonepad´s mods) and have been debugging it for 3 days...

The problem is that my build is not chorusing at all, i have signal but only a kind of "clean enhanced" signal.

The only two substitutions that i made to the original project is IC2 (tried TL082, NE5532, LM1458 and lastly the non-FET LM2904 just to check) and replaced R40 from 33 ohm to 47 ohm.
The Mix pot is working as far as i can tell, it goes from clean signal to "clean enhanced" but the depth and rate pots don´t do anything.

I have double checked all the parts orientarion, values, checked for solder joints or traces cut.
I have audioprobed the circuit from the begining to the end.
I have tweaked the 10kb trimpot and goes from distortion to clean signal, but no chorus.
I have also tried 6 different MN3007 from two different suppliers, and 2 different MN3101.
I have signal on pins 7 & 8 of the IC4 (MN3007) so i think IC is OK.
I have tried debugging the circuit @9v, 10v and 12v DC.

I think the problem is the LFO around IC2 i can´t get it to work.. i´ve tried stock version and trying to find the problem i did the Depth Mod replacing R39 (4k7) for the 22k + LED to see if the led blinked. Led stays on (dimmed but on) at all times, does not change with the depth pot, it stays fixed... i have also tweaked the feedback resistor (R34) between the 2 Opamps on IC2 with no success.

I am taking a breath from this circuit and tomorrow i will try a CMOS oscillator to R37 to see if the rest of the circuit is working... But if someone can guide me with any kind of ideas about this problem will definitely help.

My DMM readings  @ 9.03v DC are the following.

IC1 (JRC4558)
1 - 3.69
2 - 3.68
3 - 3.67
4 - 0
5 - 3.68
6 - 3.68
7 - 3.69
8 - 9.02

IC2 (TL082)
1 - 8.44
2 - 4.90
3 - 5.38
4 - 0
5 - 4.90
6 - 4.90
7 - 4.90
8 - 9.03

IC3 (MN3101)
1 - 8.96
2 - 4.51
3 - 0
4 - 4.53
5 - 0.35
6 - 7.60
7 - 3.16
8 - 0.60

IC4 (MN3007)
1 - 8.96
2 - 4.59
3 - 2.99
4 - 0.60
5 - 0
6 - 4.54
7 - 3.51
8 - 3.51

Well that´s it... Thanks in advance.

[jkokura]

Voltages look normal to me, but I'm not the BBD expert around here.

One thing that might help is giving us high quality pictures of both sides of the PCB, and also giving us a link to the documents you're using. I wasn't sure which version of the chorus you're trying to build, but the mix pot gives me a hint that it's a previous version.

Jacob

[kryoz]

Hi Jacob, thanks for your reply.

I´m using PorkBarrel_ver.2.pdf from the documents in this .zip

http://www.madbeanpedals.com/projects/PorkBarrel/docs/PorkBarrel.zip

You´re right, i will post HQ pics later.

Hernan

[kryoz]

Here are my pics... soldeing job look kind of ugly after redoing some pads...










Hope it helps.

Hernan.

[wgc]

Your pcb looks a little scratchy?  At least from the pic.  Try ohming out your traces one at a time.

[kryoz]

Yes... it looks scratchy because when i was searching for soldering hairs in between traces i cleaned it with isopropyl alcohol and brushed it with a copper brush..

i have already tested for continuity in the traces and audioprobed the circuit... but guess i am doing it again...

thanks for your reply.

Hernan.

BTW. forgot to say that R34 is lifted above IC2 because i was tweaking it with an external 50k pot, that´s why there is also 2 red cables soldered to R34 pads.

[spaceboss]

On mine (I have a thread about 20-30 or so threads down) the voltages on the Tl062 varied dramatically.

TL062
1  0 -8          8  9.48
2  4.69-4.8    7  3.25-6.97
3  2.81-6.87  6  4.79-4.86
4  0             5  4.69-4.85

I'm not familiar with the build version your working with, and I'm no circuit expert at all, but if the TL082 plays the same role as the 62, I would replace that chip first, because that seems to have a major role in the LFO.

I killed one 62 in my build and needed to swap it out to get the LFO working again.

Good luck.

[spaceboss]

Actually if you used a tlo82 at all (and it wasn't a typo) that might be the problem as the build doc for version 2 lists a tlo62. I don't know if those ICs are interchangable or not.

[kryoz]

Hi, thanks for your feedback...

Yes tl022/062/l072/082 should be interchangable they just have different specs according to power draw and noise.. but basically any dual op amp with the same pinout should fit this circuit... most common opamps used in stompboxes are these and lm1458/ne5532/jrc4558/lf353 etc etc.

i have even tried a non-fet IC like LM2904 (which worked like a charm on my phase90 to eliminate LFO noise) with still no luck..

I am building an external oscillator to test the rest of the circuit and then i think i´ll replace all parts on the LFO section one at a time to check faulty components.

I guess that problems like these are where the fun in DIY is at.

Hernan.

[kryoz]

Well, just to finish this thread, long story short... tried external oscillator, chorus came to life... lifted all parts from the LFO section, replaced with new caps and new resistors, throwed in the tl082, hooked it up... voila! flawless chorus...

Thanks you all for your feedback

Hernan.

[batak_man]

Sori sir, can you post your new debugg?

I have same problem with you
Just clean signal, when switch vibe off there no sound
and three pot doesnt work at all

Can you help to give sir

thx