Hi everyone. I'm struggling with yet another "do it yourself" guitar pedal. It is a pedal similar to Boss's CE 2 and therefore a chorus. I followed this diagram:



 from which I obtained a PCB and I also compared it with other diagrams like this: from ELECTROSMASH (which however it did not vibrate and also includes the activation of the pedal with JFET switching while I did it with 3PDT true bypass) and this one from the OP-ELECTRONICS PCB dealer site.
I did this with the addition of the R42 which if connected via the SPDT lever the pedal should have a Vibrato effect.
The problem is that I have no chorus effect when the switch connects 2 to 1 and absolute silence when the switch connects 2 to 3 of the SPST.
I checked every single component, the capacitors, resistors etc and the values ��I entered are what they should be. I also noticed a little overheating of the MN3007 IC, I cleaned it with isopropyl as much as possible and checked for shorted pins on the IC pins, but there are no problems. Now the overheating is gone (I don't want it because maybe the IC was baked).
Also from the OP-ELECTRONICS website I found documentation about it that tells us what values ��the integrated circuits should have (I wrote the ones I measured in pen): https://drive.google.com/file/d/1p1NrhVoslF6-ZRtmOuuN7325njGLOiMJ/view?usp=drive_link
As you can see pin 4 of the MN3007 and pin 8 of the MN3101 have a disproportionate voltage compared to what the documentation reports, in fact I have 8.7v and also pins 7.8 of the MN3007 instead of a fixed voltage of 3, 6v on pins 7 and 8, I have an oscillation between 6.3 and 7.7v.
In short, I did some checks on the PCB that I designed, on the components, but nothing, I can't understand it. Maybe there's something I did wrong in the schematic (the very first connection from which I then made the PCB).
Could someone enlighten me to understand where the problem might be? Thanks for any replies!

That op-electronics schematic looks like it's set up for a On-Off-On 3-position SPDT switch to me. Like that it would give you:

Up, 2 connected to 3: Standard chorus
Middle, 2 not connected: Vibrato
Down, 2 connected to 1: half way between vibrato and chorus.

The schematic looks ok, so if you're not getting any signal, I'd check that the switch wiring is actually identical to the schematic. You could audioprobe the switch and check you're getting the signals you expect. With the switch in the centre, you should have dry signal on pin3 of the switch, and delayed signal on pin 1. If you've got a 2-position switch, that won't work.

The Vgg voltage on pin 8 of the MN3101 clock chip is created inside that chip, so if that voltage is wrong, either the chip is damaged, or it's in the wrong way around, or something weird is going on. Since the other supply pins look ok, a faulty clock chip is possible.

Of course, if the clock isn't happy, then the BBD isn't happy, and if the BBD isn't happy, you'll get no delay and no chorus. So before you stress too much about the switch, we need to make sure that the clock and BBD are working and make sure you have signal coming out.

Thanks for the reply.
As can be seen from the OP-ELECTRONICS website, the switch must be an SPDT ON/ON, it is indicated both in the documentation and in the silk-screen printing of the PCB.

I checked the connections 5 times and they are correct. The biggest problem is that the MN3007 IC gets overheating and consequently the 33 Ohm resistor R52 does too.
Removing the MN3007 IC from the board and measuring the values ��on pin 8 VGG_OUT of the MN3101 there are 8.7v.
I also checked pins 2 and 4 of the MN3101, i.e. CP1 and CP2, with the oscilloscope and by rotating the RATE pot I have a sine wave that changes.

I checked for bad soldering, unwanted connections but nothing.

Could it be that the MN3007 is fake? I read about a similar problem HERE.

Quote from: anto.dima on November 22, 2023, 12:03:03 PMThanks for the reply.
As can be seen from the OP-ELECTRONICS website, the switch must be an SPDT ON/ON, it is indicated both in the documentation and in the silk-screen printing of the PCB.

Ok, but if that's the case, there's no "vibrato only" option. With the switch in the down position you get a 2:1 ratio of wet to dry, but you don't get wet-only, so it's not a pure vibrato.

QuoteI checked the connections 5 times and they are correct. The biggest problem is that the MN3007 IC gets overheating and consequently the 33 Ohm resistor R52 does too.

That's not right at all. Something is badly wrong somewhere.

QuoteRemoving the MN3007 IC from the board and measuring the values ��on pin 8 VGG_OUT of the MN3101 there are 8.7v.
I also checked pins 2 and 4 of the MN3101, i.e. CP1 and CP2, with the oscilloscope and by rotating the RATE pot I have a sine wave that changes.

I checked for bad soldering, unwanted connections but nothing.

Could it be that the MN3007 is fake? I read about a similar problem HERE.

If the Vgg voltage coming out of the MN3101 is 8.7V, then it's not only the MN3007 that's fake/broken. It should be 1/15th of the supply, in your case 9V, so 1/15 * 9 = 0.6V. 8.7V is not even close.
If you've got oscillations, that's good, but they should be clean squarewaves, not sines, unless there's something loading them very heavily.

Where did you get the chips?

Quote from: ElectricDruid on November 22, 2023, 12:53:51 PMIf the Vgg voltage coming out of the MN3101 is 8.7V, then it's not only the MN3007 that's fake/broken. It should be 1/15th of the supply, in your case 9V, so 1/15 * 9 = 0.6V. 8.7V is not even close.

Are you sure that the calculation is 1/15*9 and not 14/15*9 that I saw on the datasheet which would give me a correct value?

Quote from: ElectricDruid on November 22, 2023, 12:53:51 PMThat's not right at all. Something is badly wrong somewhere.

I directly tested the PCB in buzzer mode to check if all connections are as shown on the diagram. I've done this several times as well as comparing the two schemes. I checked the welds, cleaned well with isopropyl alcohol

Quote from: ElectricDruid on November 22, 2023, 12:53:51 PMWhere did you get the chips?

Italian Ebay Store

Agree 14/15.

The BBD should not get warm. It is not zero power, and the power does rise with frequency, but it never sucks a lot of current.

All the old BBDs were sold years ago. A few people have genuine BBDs, a lot of people sell any old chip with a BBD number over-printed.

Sorry guys, it's only 14/15ths like it says in the datasheet if you use a *negative supply* like it says in the datasheet. That's not what we're doing here. If you flip the supply rails (like in this circuit) then it's 14/15ths of the way to ground, which is 1/15th of the way above ground.

If you like, think of it as 14/15ths of -9V, so it should be -8.4V below the 9V rail. That's how the datasheet sees it, but you'll have to put the probes the other way around to get that in this situation: black to 9V, red to Vgg.

It's the same thing, of course. Voltage is relative.

Quote from: ElectricDruid on November 22, 2023, 02:51:38 PMIf you like, think of it as 14/15ths of -9V, so it should be -8.4V below the 9V rail. That's how the datasheet sees it, but you'll have to put the probes the other way around to get that in this situation: black to 9V, red to Vgg.

Yes, right. In this way I have 0,65/0,7v.
So the MN3101 haven't any problem, right?

So, could be the MN3007 a fake, Maybe it's an MN3207 disguised as MN3007. Do not you think?

No, that's still not right. That way around you should get -8.4V, not 0.6V. If you've got the black probe on +9V, there shouldn't be *any* way to get a positive reading in that circuit.

If you get -0.6V, then perhaps the clock chip is the MN3102 instead too. You might have a pair of MN3207/MN3201.

Quote from: ElectricDruid on November 22, 2023, 04:01:12 PMNo, that's still not right. That way around you should get -8.4V, not 0.6V. If you've got the black probe on +9V, there shouldn't be *any* way to get a positive reading in that circuit.

If you get -0.6V, then perhaps the clock chip is the MN3102 instead too. You might have a pair of MN3207/MN3201.

The black probe on +9V, and Red on pin 8 of the IC return a value of -0,6v.
So probability these are MN3207 and MN3201 disguised as MN3101 and MN3007!

So I had a similar problem years ago and it was indeed a counterfeit part.  I actually sent the chip to a guy overseas and he opened them up (these are the actual chips I sent him).
https://www.richis-lab.de/bbd05.htm
Not saying that's what you have, but it's possible... Have a look here for the remake 3007 by Xvive
And stay away from eBay....
https://cabintechglobal.com/semi

I solved! Indeed, as hypothesized, the ICs mentioned were fake! I received the original ones and now it works! Thank you all for the support!