Help find a small problem with Boss CE2 build with 4558 Op-Amp

[rectifier23]

Hello everyone

Just finished bulding a small clone chorus and a boss ce2. The small clone works as expected and sounds great.
The CE2 got a small problem with the 4558 Op-Amp. At first I wasn't getting any signal at all on the output.
I started working with an audio probe. After the first Q1 stage I could get a signal but later after two capacitors and
a resistor going into Pin 2 I couldn get anything out on the output of the first Op-Amp stage (Pin 1)

So I skipped the Q1, pre emphasis/hipass stage and tried to feed my guitar directly into the Op-Amp. On Pin 2 (negative Input)
I wasnt getting any sound but on Pin 3 (positive input) I suddenly got the whole thing working. The chorus effect worked with all the controls
and mods. Of course the tone was bad and there was some lfo clicking there.

I measured the Voltages on the 4558:

1: 7.78v
2: 3,77v
3: 5,03v
4: 0v
5: 5,06v
6: 5,09v
7: 2,43v
8: 8,43v

I used the vero from http://tagboardeffects.blogspot.de/2014/06/boss-ce-2.html

Here's the important part of the schematic around the 4558
http://s7.directupload.net/images/140917/6wgqnkh3.jpg

Any suggestions where the problem could be ?

[Mustachio]

Welcome to the forum rect,

The link was missing the L in html so it wasn't loading. Here ya go.

http://tagboardeffects.blogspot.de/2014/06/boss-ce-2.html

As for the circuit having no output at pin one of IC1 , not totally sure yet. Check the trace cuts under the IC make sure there isn't any continuity. Pictures of the top and bottom of the board might help us find a problem.

[PRR]

> 1: 7.78v
> 2: 3,77v

Pin 1 is an Output. It should normally be near half-supply.

Instead you have it nearly at battery voltage. It is jammed-up as high as it can go. Being jammed, it really can't wiggle your precious signal.

Why is pin 1 high? Because inverting input pin 2 is low. It really should be "same" as the non-inverting input pin 3 (which is kinda-near half-supply, as expected).

Chip op-amps don't ever fail (very-very rarely, if bought from reputable vendors).

Something is wrong with the stuff connected to pin 2.

My sore gut likes a backward or leaky C2.

But there is other stuff you cut-off the "important part" which could also be dragging it down.

[rectifier23]

Thanks for the replies everyone. I thought that 7.78v on Pin 1 is way too high. Especially if compared to voltages of other CE2 builders.
Listen to the quick soundsample I've made. This is my guitar connected straight to Pin 3 --> http://picosong.com/9uF4/
I'm turning the rate knob, switching on the vibe mod afterwards, then back to chorus. Everything seems to work. But of course the sound is bad
without the pre emphasis/hipass stage. My guitar also has an preamp build in, if I turn it on I have no sound even when connected to Pin 3 (Low input impendance )

Two days ago I took 2 hours of time and measured every component with a multimeter. The solder points should be fine but I couldn't measure the capacitors. I only check the legs of them if they're properly connected.
So maybe there is a faulty capacitor somewhere.

Here are some pics:

http://s1.directupload.net/images/140917/d62c625q.jpg
http://s14.directupload.net/images/140917/wcalioh3.jpg

...I need to get a new soldering iron though  

Forget the schematic I posted before. This is the schematic the vero is based on: http://www.electrosmash.com/images/tech/ce-2/boss-ce-2-schematic-true-bypass.png
The Pins of the 4558 are wrong though. 1 should be output not  3

[duck_arse]

it looks like yr soldering iron is doing a fine job, bright and shiny, but you need to steel-wool your vero before you solder (after all the cuts is good). this alone will improve the solders, and stop the blobby's.

and if you are going to use sockets, push the IC's in! they will go clunk, and sit lower than the one at the top of yr photo.

[rectifier23]

> 1: 7.78v
> 2: 3,77v

Pin 1 is an Output. It should normally be near half-supply.

Instead you have it nearly at battery voltage. It is jammed-up as high as it can go. Being jammed, it really can't wiggle your precious signal.

Why is pin 1 high? Because inverting input pin 2 is low. It really should be "same" as the non-inverting input pin 3 (which is kinda-near half-supply, as expected).

Chip op-amps don't ever fail (very-very rarely, if bought from reputable vendors).

Something is wrong with the stuff connected to pin 2.

My sore gut likes a backward or leaky C2.

But there is other stuff you cut-off the "important part" which could also be dragging it down.

Thanks you for the response PRR. Today I'll try to remove C2 and replace it with another capacitor. What components could drive the voltage to 7.7v on Pin 1 ? Could it be something related to R4, R5 and R6 ?

http://www.electrosmash.com/images/tech/ce-2/boss-ce-2-schematic-true-bypass.png

[Seljer]

Like mentioned, pin 1 is high because pin 2 is low. So the thing you should be pondering is why is pin 2 low.


The current over R6 = (7.78volts-3.8volts)/47kiloohms = 0.084milliamperes


R5 is wired in series with C3 so there can't be any DC current flowing over it, the input of the opamp has a very high impedance so that means that 0.084mA is flowing over R4. Doing the math with U = I*R, that means that the far side of R4 next to C2 is for some reason at 0V, shorted to ground.

So yes, check C2 (remove it and measure the voltage without it installed) or any solder bridges or incomplete/forgotten cuts in the veroboard around C2 and R4.


The voltages on the other half of the opamp is also a bit funny, but they'd be explained by a waterfall effect from the first half acting up. Pin 1 from the first half is high, which is also pulling pin 6 (the negative input) *slightly* high which is making pin 7 go low. Fix the first half of the opamp and this issue will disappear.