EA tremolo no sound

[villano666]

Hi! I've build a EA Tremolo based on this schematic


I've made my own pcb



The problem is that with the effect on (i can see the led on) I have no sound no matter what i do with any of the three knobs. With the effect off I get clean sound.
These are the voltages I'm getting:

Q1	Q2	Q3	Q4
5,57	0	oscilating up to 6V	9
1,48	0	0,56	5,2
0,99	0,66	0	3

I've believe these values are ok, I'm not sure about Q2 non 0V, which oscilates only between 0,3 and 0,66 no matter what I do with depth knob.
I haven't solder my wires they are only twisted to most of the 3dpdt but I don't think that's the problem, I've tested continuity accross the wires and everthing looks normal.

Any ideas what could be happening?
Thanks

[antonis]

Q2 Gate should follow Q3 Collector in a percentage set by (R19 + lower R13 setting) / (R19 + R13 + R7)..

Q1 Base should stand at 1.9V (can't say if your DMM's impedance loads R3..) but, as it is, Q1 marginally is between slightly ON & OFF regions..
(480mV V_BE don't indicate a happy working BJT..)
Of course, Q1 Collector quiescent voltage is OK and you should have output for input positive signal waveform..
(like reverse half rectified amplified signal..)

[duck_arse]

.... and, antonis, what else do we say? yes, photos. please show us some photos of what you have built, so we can see parts values and solder joints and off board wirings.


and welcome to the forum.

[villano666]

Q2 Gate should follow Q3 Collector in a percentage set by (R19 + lower R13 setting) / (R19 + R13 + R7)..

Q1 Base should stand at 1.9V (can't say if your DMM's impedance loads R3..) but, as it is, Q1 marginally is between slightly ON & OFF regions..
(480mV V_BE don't indicate a happy working BJT..)
Of course, Q1 Collector quiescent voltage is OK and you should have output for input positive signal waveform..
(like reverse half rectified amplified signal..)

I'm not quite sure to understand, I know Vbe should be 0.7 to get activated, so 480mV is not enough. Could that be because of a Q1 malfunction? Should I replace it or is it something else?

Here are some pictures, as I said 3pdt wires are only twisted as I haven't drilled the enclosure yet and wires are not adjust to their final lenght. I just wanted to do a quick test before placing this in the enclosure. Could that be the problem?




I've checked the entire bord for short circuits, couldn't find one.

Thanks!

[antonis]

.... and, antonis, what else do we say?

Other than "Welcome"..?? 

Beware of the, by a whisker, shorts..!! 



P.S.
Plz also post an item side of your PCB..
(as it is, it calls for a double sided PCB.. probably, 3 X 1μF LFO non-polarized caps are box-type and not electrolytics, as appeared on PCB layout..)

[villano666]

Yeah, I've checked those haven't found nothing. I don't know where to go.

[antonis]

Yeah, I've checked those haven't found nothing. I don't know where to go.

https://www.diystompboxes.com/pedals/debug.html

https://www.diypedalgearparts.com/en/novita/26_Audio-probe-how-to-build

https://www.youtube.com/watch?v=jWvIfDSxbIk

[villano666]

Great info, thanks!
I'm gonna build a probe and test the circuit.

[willienillie]

pot(s) got solder in the lug rivets? we don't allow solder wires to the rivets, no matter how enticing they appear - it causes too many problems.

[villano666]

pot(s) got solder in the lug rivets? we don't allow solder wires to the rivets, no matter how enticing they appear - it causes too many problems.

I'll fix that as well, thanks!

[villano666]

P.S.
Plz also post an item side of your PCB..
(as it is, it calls for a double sided PCB.. probably, 3 X 1μF LFO non-polarized caps are box-type and not electrolytics, as appeared on PCB layout..)

here it is, sometimes i use the one that fits for the hole separation, not exactly the model I'm going to install.

[villano666]

I've fixed it! Took your advice, built an audio probe and found that I've installed a ceramic C9 instead of an electrolitic one. Changed caps, worked like a charm 
Thank you so much for your help!

I'll leave you some images of the probe I put together.