Echo base debugging

[Les_Portes]

Hi everyone,

I have been debugging this one for a while now, and I believe I'm very close to completing it ! I am following the veroboard schematic, here : http://www.sabrotone.com/?attachment_id=977

I had to replace the 2N5089 by a 2N5088 and the 2N5087 by a BC560 (which I therefore mounted the other way, CBE from top to bottom), as advised by my local provider who had a shortage. My 4066 reference is MC14066BCP.

It now works if I remove the 4066 and SC pin 1-2 & 3-4, but the sound's distorted. Every pot work, the LED does to if I SC 8-9 as well, the sound comes out delayed & modulated, but it is distorted (saturated ? not sure of the word here).

Here is the voltage readout - please note my multimeter is low quality and messes the reading on high resistors, as I understood thanks to one of the debugging topic on this pedal I read
4066 socket short circuited 1-2/3-4
1-4  2.85V
5     0.39V
6-7  0
8     4.93V
9-12 0
13    7.5
14    9.16

TL072 Modulation
1    4.2 - 5.5
2-3 4.99
4    0.7-0.82
5    4.06
6    0-7
8    8.3

TL072 the other one
1-2 4.99
3    4.97
4    0
5    2.47
6-7 4.99
8    9.16

And the PT2399
1       4.99
2       2.48
3-4    0
5       3.06
6       2.48
7-8    0.5-0.8
9-13  2.48
14     2.52
15-16 2.48

If I put back the 4066 the voltage readout of the 4066 is
1-2    2.85
3-4    2
5       0.39
6-7    0
8       4.4-5.6
9-12  0
13     7.50
14     9.16

The 4066 socket works correctly (it was one of the issues already encountered I read about)

I will try to get a replacement 4066 tomorrow in case the part is faulty, but if you have other leads I'm all ears

[Les_Portes]

Transistor Q2 was broken, I replaced it with a 2N5089 2 days ago

I know have the following behavior

• All pots work
• With effect on I get modulated delay, but it's saturated
• With effect off I get the trails, but I don't have any clean signal coming through (so it goes silent)

Here is the complete voltage & audio read out
https://drive.google.com/open?id=1GTNrFAktlwQ20oZNnPnsPgDN3OwCyyMoh4F8JGx3CBE

Any help would be highly appreciated, I am running in circles here

[slacker]

Nice spreadsheet, your voltages look Ok, pin 5 of the audio TL072 looks low but like you said that's just your meter. I would check the component values and the connections around pins 13 and 14 of the PT2399, if the 47k resistor was too large or has a bad connection that could cause the distortion.
If you're getting no dry signal at the output check that R11 and the dry switch are connected correctly and that the dry switch works. If you haven't fitted the dry switch then you need to add a wire connecting Dry SW 1 to Dry SW 2 otherwise you will have no dry. If the dry switch is set to kill the dry then you will have no dry in bypass either, the switch is a bit of a dirty hack.

[Les_Portes]

Awesome ! Thanks a lot for the info, indeed I did not connect the dry switch, so that's one mystery solved already

I will follow your advices and keep you posted.

Thanks again !