Need help with zombie chorus

[jamal]

Hello everybody, new here at the forum. I'm having trouble with a pedal I just built. Here are the schematics: http://www.sabrotone.com/?attachment_id=3129. I can get the "dry" (Clean) signal throw but not the altered one. I did some audio probing and I discovered that th eproblem is on C1. The thing is, when I attach the battery to the circuit, the signal can't get through C1. However, when deattach the battery, the signal gets through C1 and into the input of U1. Could anybody please help me out and tell me what could cause this?
Many thanks.

[midwayfair]

Take voltages on each pin of each chip. See here for the format and information we need:
http://www.madbeanpedals.com/forum/index.php?topic=902.0

You will also need to locate the actual schematic for the effect -- what you linked to is a layout. You'll need the schematic so we can all be sure we're referencing the same part numbers.

Although this is simple as far as chorus pedals go, it is simply too complicated a pedal to guess what might be wrong from the description of the problem. Keep your audio probe handy, though, it will be helpful.

Since this is a vero build, you should also take and post pictures of both sides of your board, and make sure -- using the continuity (beep) setting on your multimeter (NOT your eyes!) -- that your cuts are all made properly and thoroughly.

[flanagan0718]

Hey man,
   I've built a few of these (this exact layout) and it's a very touchy build. First make sure you have the trace cut under R4. It's a little tough to see but there is a cut there. Also double check the electro caps and diode orientation. In order to diagnose the issue further please post some pictures of the board front and back. This will help pinpoint the problem. Also take some voltage readings off the ICs if possible.

-Mike-

EDIT: What Jon said.   

[jamal]

Thanks for replying so quickly! I did have in account the trace cut under R4 and I checked the polarity's on the caps and on the diode. As far as the schematic goes, I'm sorry but I can't find one that uses the same components as the ones in this layout but I will have pics and the ic's voltages up in 5 min, along with the names of each IC. The values of each cap and resistor are described under the layout. The only replacement is the diode. I'm using a 1N4003 as a replacement for the 1N4001.

[flanagan0718]

Other cuts hard to see on the layout are R20, R18, R8

[jamal]

Pics:

[jamal]

Voltages:
U1(TL072CP):
P1 - 7.42 V
P2 - 7.42 V
P3 - 7.32 V
P4 - 7.85 V
P5 - 7.33 V
P6 - 7.31 V
P7 - 7.33 V
P8 - 8.79 V

U2(MN3007)
P1 - 8.78 V
P2 - 8.78 V
P3 - 7.32 V
P4 - 0 V
P5 - 0 V
P6 - 0 V
P7 - 6.89 V
P8 - 6.90 V
U3 AND U4 coming up in a sec

[Scruffie]

Check R12... is it going to the right holes? Your V.Ref is way off.

[jamal]

U3(TL072CP)
P1 - 1.4-8.0 V
P2 - 5.26-5.42 V
P3 - 4.0-6.87 V
P4 - 0 V
P5 - 5.27-5.42 V
P6 - 1.45 V
P7 - 4.4 - 6.8 V
P8 - 8.77 V

U4(CD4046BE)
P1 - 8.76 V
P2 - 0 V
P3 - 0 V
P4 - 4.42 V
P5 - 0 V
P6 - 1.03 V
P7 - 1.03 V
P8 - 0 V
P9 - 5.22 - 5.80 V
P10 - 4.24-4.71 V
P11 - 4.14 - 4.72 V
P12 - 6.85-6.88 V
P13 - 8.76 V
P14 - 2.92 V
P15 - 0 V
P16 - 8.76 V

[jamal]

Yes, R12 is in the right holes

[Scruffie]

Pin 14 of the 4046 should be connected to pin 16 and both to 9V so there's an issue there, until that's fixed your clock isn't working, LFO looks fine though.

[jamal]

Thanks scruffie, the voltage on pin 14 is now the same as in pin 16 (bad contact) but I still don't have the modulated signal, only the clean signal.

[midwayfair]

sorry for the derail, but I need (NEED) that blue perfboard for ... reasons. Can you tell me where you got it?

[Scruffie]

Thanks scruffie, the voltage on pin 14 is now the same as in pin 16 (bad contact) but I still don't have the modulated signal, only the clean signal.

Okay do you now have about half supply on Pins 2 & 6 of the 3007?

If so then you need to find out why the bias on U1 pins 5, 6 & 7 is so high (1, 2 & 3 are biased by the BBD output so once those are fixed they should hopefully correct).

[jamal]

I'm sorry but it belonged to a friend of mine's dad. And i don't really have a way to contact him now but on the side, it says BICC vero no. 03-27557B