Zombie chorus no modulate sound

[2tonewarrior]

Hi,

I´ve made this zombie chorus (http://solderman.fatabur.se/Never%20Mind/Nevermind%20project%20file.pdf) and I get a clean sound both in bypass and with the effect on. I´ve reviewed all two or three times.

Does anyone know how to solve this? Maybe the problem can be a fake mn3007? I´ve bought 5 pieces from ebay (I know, I know... the best place to get a fake chip, but the seller had 99,8% positive feedback)

[Scruffie]

Feedback score means absolutely nothing regards fake or real chips, people buy, get them, leave good feedback and don't test them for ages and they probably sell a lot of legitimate items.

Back to your chorus... voltages.

[2tonewarrior]

Feedback score means absolutely nothing regards fake or real chips, people buy, get them, leave good feedback and don't test them for ages and they probably sell a lot of legitimate items.

Back to your chorus... voltages.

Thanks for the quick reply. I am out for weekend on my parent´s house and don´t have a DMM right here, I´ve bring the guitar and various pedals but not the multimeter, my bad. I´ll post the voltages on Sunday.

[2tonewarrior]

Sorry for the delay, here are the voltages (both pots set to max):

IC1 (TL082)

1 - 4,9
2 - 4,9
3 - 1
4 - 0
5 - 1,48
6 - 1,48
7 - 1,48
8 - 8,78


IC2 (MN3007)

1 - 8,81
2 - 0
3 - 4,9
4 - 0
5 - 0
6 - 8,79
7 - 6,2
8 - 6,2


IC3 (CD4046)

1 - 0
2 - 0
3 - 8,88
4 - 8,88
5 - 0
6 - 0
7 - 1,47
8 - 0
9 - 0,13
10 - 0,51
11 - 0,46
12 - 6,94
13 - ---
14 - 8.82
15 - ---
16 - 8,82


IC4 (TL082)

1 - 8,08
2 - 4,86
3 - 4,86
4 - 0
5 - 4,86
6 - 1,49
7 - 1,46
8 - 8,76

[Scruffie]

Few problems... first off, your clock isn't working (4046) I don't know that chip too well but you should have approximatley half voltage on pins 2, 3 & 4 and on 2 & 6 on the 3007.

Your OpAmp isn't biased right, I assume that's just because you haven't set the bias trimmer to approximatley half way or wrong value perhaps?

Is your LFO OpAmp voltage moving? It shouldn't be fixed like that... a TL082 might not be the best for the job and causing it to lock up.

[2tonewarrior]

So what could be the problem? 

There is no trimmer to adjust and the OpAmp voltage is not moving.

[Scruffie]

Oh it's the really old one... really should have a trimmer but playing along...

Are R6,7,8 & 9 all 47k? Check... i'll take Pin 3 of IC1 being so low due to a false DMM reading due to the impeadance.

No voltage movement or proper clock voltages... could be any number of things, bad solder joint or solder hair shorting something... the LFO might not work well with a TL082 and need a lower power opamp like a 1458, you might have damaged the 4046 with static.

Try removing the 3007 and check the voltages on pin 2 & 6 again, if the voltages still aren't half supply here, your 4046 is causing your issue.

[2tonewarrior]

Oh it's the really old one... really should have a trimmer but playing along...

Are R6,7,8 & 9 all 47k? Check... i'll take Pin 3 of IC1 being so low due to a false DMM reading due to the impeadance.

No voltage movement or proper clock voltages... could be any number of things, bad solder joint or solder hair shorting something... the LFO might not work well with a TL082 and need a lower power opamp like a 1458, you might have damaged the 4046 with static.

Try removing the 3007 and check the voltages on pin 2 & 6 again, if the voltages still aren't half supply here, your 4046 is causing your issue.

Resistences checked, all correct value.

Voltages on 4046 are basically the same without the mn3007, I think a´m gonna try to find a new mn3007 in my town, and a new 4046 and if with those 2 new chips the pedal doesn´t work i´m gonna do other version. I only wanted to do this version because it houses on a 1950a.

Back to the OpAmps. Some guy in a spanish forum suggest tl062s, would they work better?

[Scruffie]

Oh it's the really old one... really should have a trimmer but playing along...

Are R6,7,8 & 9 all 47k? Check... i'll take Pin 3 of IC1 being so low due to a false DMM reading due to the impeadance.

No voltage movement or proper clock voltages... could be any number of things, bad solder joint or solder hair shorting something... the LFO might not work well with a TL082 and need a lower power opamp like a 1458, you might have damaged the 4046 with static.

Try removing the 3007 and check the voltages on pin 2 & 6 again, if the voltages still aren't half supply here, your 4046 is causing your issue.

Resistences checked, all correct value.

Voltages on 4046 are basically the same without the mn3007, I think a´m gonna try to find a new mn3007 in my town, and a new 4046 and if with those 2 new chips the pedal doesn´t work i´m gonna do other version. I only wanted to do this version because it houses on a 1950a.

Back to the OpAmps. Some guy in a spanish forum suggest tl062s, would they work better?

If the voltages are the same without the 3007, I wouldn't go looking for a new one just yet or bother replacing the one in there, it may very well be fine, your 4046 however, is not, for any of the reasons given, damaged or being shorted by something etc.

Yeah a TL062 may be better, a LM1458 or LM358 would also probably be reasonable substitutes. But it could be the 4046 stopping the LFO working, get the clock to work first then sort the rest.

I'm gunna be honest here... this may fit a 1590A but i'm not sure how great it's gunna be, the zombie chorus is seriously stripped down, it has no bias for the 3007 so you can't trim out any distortion, the filtering is lax so it'll be noisy and hitting the strings hard will most likely clip the BBD, the LFO is at great risk of ticking etc. Then again it may suit your needs perfectly and i'm being fussy.

Another option (although not analog and some claim to have issues with) would be Rick Holts Little angel chorus, that'll fit a 1590A and is a much simpler build, it uses a PT2399 or you could wait for Madbeans Pork Rind chorus.

[2tonewarrior]

Thanks for your time, you are helping me out a lot. I see now that I definitely should have built another version  but I´m gonna try to finish this build. I will buy a new clock tomorrow and see what happen.

I´ve buy some PT2399s from tayda in my last order and I had Little Angle as a someday todo, looks very good. Madbean´s builds are always a great deal. If the zombie fails at last I´ll do one of these two, probably Pork Rind if available.

[2tonewarrior]

Unlucky   Changed the clock and the 2 OpAmps, checked the solder joints (just in case), .... and nothing. The voltages are the same and the sound too.

[Scruffie]

Right, no broken parts so we're looking for something in the build that's wrong.

Can you post clear photos of the top and bottom of the circuit? An extra set of eyes can help.

Wrong value, broken trace, solder bridge/hair, bad joint wrong polarity component is the sorta stuff you should be looking for now, even though you've looked before.

[2tonewarrior]

Right, no broken parts so we're looking for something in the build that's wrong.

Can you post clear photos of the top and bottom of the circuit? An extra set of eyes can help.

Wrong value, broken trace, solder bridge/hair, bad joint wrong polarity component is the sorta stuff you should be looking for now, even though you've looked before.

Sorry for the delay Scruffie, I´ve been busy at work. I´ll post photos as soon as possible.