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.
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.
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. :)
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.
Other cuts hard to see on the layout are R20, R18, R8
Pics:
(http://i62.tinypic.com/4fzu60.jpg)
(http://i58.tinypic.com/bjhldw.jpg)
(http://i58.tinypic.com/2v3t09k.jpg)
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
Check R12... is it going to the right holes? Your V.Ref is way off.
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
Yes, R12 is in the right holes
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.
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.
sorry for the derail, but I need (NEED) that blue perfboard for ... reasons. Can you tell me where you got it?
Quote from: jamal on February 18, 2015, 05:12:45 PM
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).
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
U1(TL072CP):
P1 - 7.46(And then decreases constantly until 0, than starts again) V
P2 - 7.42(same as above) V
P3 - 0.98 V
P4 - 7.8 (Sometimes changes) V
P5 - 1.06 V
P6 - 5.22 V
P7 - 5.22 V
P8 - 8.71 V
U2(MN3007)
P1 - 8.71 V
P2 - 8.71 V
P3 - 5.22 V
P4 - 0 V
P5 - 0 V
P6 - 0 V
P7 - 6.72 V
P8 - 6.72 V
U3(TL072CP)
P1 - 4.9-5.70 V
P2 - 5.18 V
P3 - 5.1-5.34 V
P4 - 0 V
P5 - 5.18 V
P6 - 1.51 V
P7 - 5.39 - 5.42 V
P8 - 8.70 V
U4(CD4046BE)
P1 - 0 V
P2 - 4.29 V
P3 - 4.36 V
P4 - 4.36 V
P5 - 0 V
P6 - 0.93 V
P7 - 0.93 V
P8 - 0 V
P9 - 5.14 - 5.17 V
P10 - 4.27-4.30 V
P11 - 4.45 - 4.49 V
P12 - 6.79 V
P13 - 0 V
P14 - 8.69 V
P15 - 0 V
P16 - 8.69 V
Well fixing that fixed the bias issue on U1 and you also have the proper clock voltages, so something between the 3007 pins 2 & 6 and 4046 pins 2, 3 & 4 is going wrong, probably just another bad joint.
Possibly a short between pins 1 & 2 of the 3007 too seeing as they're both at supply.
I know get on the 4046:
P2 - 8.69 V
P3 - 0 V
P4 - 4.36 V
And on the 3007
P2 - 0 V
P6 - 0 V
Is that correct?
sorry, 8.68 for P2 of the 3007
No, pins 2,3 & 4 of the 4046 should be approx 1/2 supply as in your previous readings, as should pins 2 & 6 of the BBD.
well I'm getting kind of annoyed here. The voltages on those pins, if i move the board a little or if some minutes pass, they have the right values, but then, hey return to the wrong values
Then you probably have a bad solder joint
well i now get the right voltages but still no noticeable modulated sound.
I assume you're the same member debugging a zombie chorus on freestompboxes? If so as I said your BBDs are likely fake.
Yes I am, and i guess you are right, I just used my audio probe on the 3007 and the output sounds exactly the same as the input. That means it's a fake right? Btw, do you know if it can be replaced by a nte1641?
Quote from: jamal on February 18, 2015, 08:21:35 PM
Yes I am, and i guess you are right, I just used my audio probe on the 3007 and the output sounds exactly the same as the input. That means it's a fake right? Btw, do you know if it can be replaced by a nte1641?
are you in the states? If so, I have one or two I could part with.
NTE1641 should be fine.
Sorry flanagan, europe here. And thanks for all the help Scruffie, it was very valuable.