Building the Echo Base PCB

[lordanthony]

I'm having great difficulty getting my echo base up and running. The led doesn't come on and I get no sound. An audio probe shows a clean signal on pins 1,2 and 3 of u3 TL072 and pins 1 and 2 of CD4066. I get a weird sound on the other pins here and on the pt2399. I've uploaded a video so you can see what I mean.

Pin readings as follows:
U1:TL072
4.91
5.03
5.03
0.89
4.84 - 4.99
5.03
5.04
8.87

U2:PT2399
5.03
2.51
0
0
2.90
2.51
3.16
3.17
2.51
2.51
2.51
2.51
2.51
2.54
2.51
2.51

U3: TL072
5.03
5.03
4.57
0
5.03
5.03
5.03
9.78



U4: CD4066
4.68
4.68
0.68 - 0.72
0.72 - 0.75
0
off:0.47-0.49 on:4.64-4.65
0
off:1.68 on:4.89
off:0 on:1.67
4.68
4.68
9.56
9.36
9.77

2n5089
E:on:0 off:0
B:on:0 off:0.61
C:on:9.33 off: 0.95

BC560
1.53
0.96
0

7805
0 (retested - 5.02)
0
9.75

I've used most of the mods from the guide: dry kill, diode lift switch, dub switch, waveform pot, modulation switch.

If anyone can suggest where to look I'd be really grateful.


Can any one suggest what's going on?

[Taylor]

One thing that looks weird is that your 5v rail seems to be present, i.e. on pin1 of the PT2399, but according to your reading the 7805 regulator is not putting out 5v (should be present on the left pad). I'd guess maybe you just didn't get a good reading on the regulator - sometimes solder flux will prevent a good reading so you need to use the sharp points of your probe leads to really stab the solder joint. Try measuring again - I'm pretty sure you'll get 5v there.

Is this your first build? Can you post a pic?

[lordanthony]

Hi Taylor

Yes, you're quite right. The 7805 is giving out 5.02 which now you mention it does make sense.
I've built 6 pedals so far and started about 6 weeks ago so am attempting to learn as i go.

Photos of the build:




Note that pin 11 of the 4066 does not appear to have much solder but I have tested continuity with the (1.5m?) resistor and it appears sound.

It's 1.30am here so am going to sleep now, but thanks for looking into this.

[lordanthony]

I've tried to follow the schematic to trace the signal input and I would assume that I should be getting clean sound from the guitar on U3 at pins 5, 6 and 7? This is where I get the horrible sound as shown on the video I posted. I do however get sound on Pins 1,2 and 3 (Pin 3 toggles depending on the bypass switch), which I understand to be pretty much near the output of the circuit. Have I misread the schematic?



Another question re the schematic - is there a way to identify which components are next in the path where there is more than one possible component? eg the 47u capacitors.

[slacker]

Can't see your video, it's private you need to make it public so we can see it.

The opamp top left on the board, under the level pot is the input and output stages. With the dry kill switch closed, ie: dry not killed you should clean signal on pins 1 and 7 no matter what position the bypass switch is in. See here for the pin out for opamps to make sure you're checking the right pins http://tangentsoft.net/elec/opamp-tester.html

Hopefully the video will give more clues as to what is wrong.

[lordanthony]

Oh man, I've made the video public now - thanks for pointing it out.
I'm getting signal from 1, 2 and 3 on the top left chip, nothing on the other pins, including 7.

[Fine Mechanics]

Hi guys. First post here!

I'm a relative newb. After building a couple of kits I've now moved onto the echo base. First 'proper' build sourcing parts, drilling and decorating the enclosure from scratch, etc.

Waiting on some final parts, but all being well I'll be looking at a finished build before the weekend. One tweak that I'd like to make to my pedal is to add a 'drive' control that will adjust the amount of distortion on the repeats. I'm planning to achieve by tweaking the diode lift mod shown in the schematic; I'm hoping that someone can sense check my approach:

- Replace the SPST with a 10k pot wired as a variable resistor to control drive level.
- Add second pair of 1n914s in series with the existing pair to increase the amount of drive available for a more noticeably distorted effect. 

It'd be awesome if someone more experienced than myself could confirm whether or not this approach makes sense.

All help much appreciated in advance! I'll be sure to share photos and some clips once my build's done.

[Taylor]

I've tried to follow the schematic to trace the signal input and I would assume that I should be getting clean sound from the guitar on U3 at pins 5, 6 and 7? This is where I get the horrible sound as shown on the video I posted. I do however get sound on Pins 1,2 and 3 (Pin 3 toggles depending on the bypass switch), which I understand to be pretty much near the output of the circuit. Have I misread the schematic?



Another question re the schematic - is there a way to identify which components are next in the path where there is more than one possible component? eg the 47u capacitors.

The 47uf caps are for power supply filtering, so they're not part of the audio path and you won't get any audio there even with a functioning pedal. This is generally true so when you're looking at schematics you can usually see that the largest electrolytic caps will be connected to power pins on ICs.

I should note here that the individual opamp packages labeled U3A and U3B on the schematic are in fact swapped on the PCB. So, the input section on the PCB is actually U3A with pins 1, 2, and 3. The output is U3B with pins 5, 6, and 7.

When probing, I'd recommend that you try to separate the different sections and look at outputs for each section. So check for the signal at pin 1 of the top left opamp on the board, then pin 2 of 4066, then pin 10 of 4066, then pin 7 of the top left opamp. If you can compartmentalize to find the problem areas, then you can focus in on them. It's tough because with your build it sounds like possibly all of the sections are not functioning. If possible, what I'd do personally is undo all the mods and get it working stock, then add the mods back once you know the circuit is functioning. It's going to be difficult to guess what's causing the problem with all the mods in place. Or at least double check to make sure you don't have something like the clean kill is activated (no clean signal) plus the level is turned down so you have no delay signal.

[Taylor]

Hi guys. First post here!

I'm a relative newb. After building a couple of kits I've now moved onto the echo base. First 'proper' build sourcing parts, drilling and decorating the enclosure from scratch, etc.

Waiting on some final parts, but all being well I'll be looking at a finished build before the weekend. One tweak that I'd like to make to my pedal is to add a 'drive' control that will adjust the amount of distortion on the repeats. I'm planning to achieve by tweaking the diode lift mod shown in the schematic; I'm hoping that someone can sense check my approach:

- Replace the SPST with a 10k pot wired as a variable resistor to control drive level.
- Add second pair of 1n914s in series with the existing pair to increase the amount of drive available for a more noticeably distorted effect. 

It'd be awesome if someone more experienced than myself could confirm whether or not this approach makes sense.

All help much appreciated in advance! I'll be sure to share photos and some clips once my build's done.

Hey, welcome. 

By adding diode pairs in series, you actually raise the clipping threshold, which means you'll have less distortion at a given signal level, not more. You could try some germanium diodes instead of silicon, as they have a lower forward voltage, which translates to clipping threshold in this instance.

You could also try increasing the gain coming out of the PT2399, by changing the 47k to the right of the 2399 to a larger value, but I suspect this could disturb the functioning of the feedback and/or cause distortion in the analog switches. Maybe Slacker can comment? I don't see another simple way to increase distortion there.

[Fine Mechanics]

Hi guys. First post here!

I'm a relative newb. After building a couple of kits I've now moved onto the echo base. First 'proper' build sourcing parts, drilling and decorating the enclosure from scratch, etc.

Waiting on some final parts, but all being well I'll be looking at a finished build before the weekend. One tweak that I'd like to make to my pedal is to add a 'drive' control that will adjust the amount of distortion on the repeats. I'm planning to achieve by tweaking the diode lift mod shown in the schematic; I'm hoping that someone can sense check my approach:

- Replace the SPST with a 10k pot wired as a variable resistor to control drive level.
- Add second pair of 1n914s in series with the existing pair to increase the amount of drive available for a more noticeably distorted effect. 

It'd be awesome if someone more experienced than myself could confirm whether or not this approach makes sense.

All help much appreciated in advance! I'll be sure to share photos and some clips once my build's done.

Hey, welcome. 

By adding diode pairs in series, you actually raise the clipping threshold, which means you'll have less distortion at a given signal level, not more. You could try some germanium diodes instead of silicon, as they have a lower forward voltage, which translates to clipping threshold in this instance.

You could also try increasing the gain coming out of the PT2399, by changing the 47k to the right of the 2399 to a larger value, but I suspect this could disturb the functioning of the feedback and/or cause distortion in the analog switches. Maybe Slacker can comment? I don't see another simple way to increase distortion there.

Thanks for the response Taylor, it's appreciated.

After revisiting some articles about diode clipping, I now see where I was getting my logic mixed up assuming that adding diodes would increase clipping. Thanks for the tip on the Germaniums. Short term I think I'll wire a pair of Germs and the pair or 1n914s  onto a DPDT to switch between lift, standard and germanium drive settings, adding in the pot later if necessary. If it sounds any good I'll post clips.

Driving the output of the pt2399 definitely sounds interesting - looks like an evening of Googling awaits! Adding some kind of input boost and output attenuation circuits similar to the Moog delay also seems like an option which may warrant further investigation.

[lordanthony]

I've tried to follow the schematic to trace the signal input and I would assume that I should be getting clean sound from the guitar on U3 at pins 5, 6 and 7? This is where I get the horrible sound as shown on the video I posted. I do however get sound on Pins 1,2 and 3 (Pin 3 toggles depending on the bypass switch), which I understand to be pretty much near the output of the circuit. Have I misread the schematic?



Another question re the schematic - is there a way to identify which components are next in the path where there is more than one possible component? eg the 47u capacitors.

The 47uf caps are for power supply filtering, so they're not part of the audio path and you won't get any audio there even with a functioning pedal. This is generally true so when you're looking at schematics you can usually see that the largest electrolytic caps will be connected to power pins on ICs.

I should note here that the individual opamp packages labeled U3A and U3B on the schematic are in fact swapped on the PCB. So, the input section on the PCB is actually U3A with pins 1, 2, and 3. The output is U3B with pins 5, 6, and 7.

When probing, I'd recommend that you try to separate the different sections and look at outputs for each section. So check for the signal at pin 1 of the top left opamp on the board, then pin 2 of 4066, then pin 10 of 4066, then pin 7 of the top left opamp. If you can compartmentalize to find the problem areas, then you can focus in on them. It's tough because with your build it sounds like possibly all of the sections are not functioning. If possible, what I'd do personally is undo all the mods and get it working stock, then add the mods back once you know the circuit is functioning. It's going to be difficult to guess what's causing the problem with all the mods in place. Or at least double check to make sure you don't have something like the clean kill is activated (no clean signal) plus the level is turned down so you have no delay signal.

Thanks for your reply. I took the mods off - still no luck. Then reseated the 4066 a few times and it sprung into life!
I hhave now put all the mods back in and the sound is still fine but I'm only getting 0.3v on the LED, on or off. I'm much further forward than I was before though, so really pleased.

Thanks for your help.

[Taylor]

Thanks for your reply. I took the mods off - still no luck. Then reseated the 4066 a few times and it sprung into life!
I hhave now put all the mods back in and the sound is still fine but I'm only getting 0.3v on the LED, on or off. I'm much further forward than I was before though, so really pleased.

Thanks for your help.

Cool, and, no problem.  I'm always happy to help when I can, but I don't necessarily know the answer to every question. Even after building stuff for a number of years, I still consider myself a student.

So, your audio is working pretty much as it should, but no LED? Do the bypass switching and LFO work?

What type of LED do you have? The 50k resistor to the right of the 4066 is the current limiting resistor for the LED. Depending on your LED type, you may just need to lower this value to get it to start lighting up. Try something like a 1k. If it's now very bright, use a value in between. If it still doesn't light, the issue is probably in the area around the 4066, or the LED could be in backwards perhaps.

[lordanthony]

So, your audio is working pretty much as it should, but no LED? Do the bypass switching and LFO work?

What type of LED do you have? The 50k resistor to the right of the 4066 is the current limiting resistor for the LED. Depending on your LED type, you may just need to lower this value to get it to start lighting up. Try something like a 1k. If it's now very bright, use a value in between. If it still doesn't light, the issue is probably in the area around the 4066, or the LED could be in backwards perhaps.

I did play around with different values for the CLR and got a good result with an 8k - it was working fine when all the mods were taken out but it stopped after I'd put them back in. The mods themselves are all working as they should; LFO switch and pot, diode lift, clean kill etc. However, I think I'll be ok finding the LED problem myself now.  It was good to talk the whole thing through with someone - your advice was really appreciated. Thanks for your help again.

[Fine Mechanics]

Finished mine today, but still some troubleshooting required.

I'm only getting a single repeat and the modulation doesn't work. The speed knob seems to control the pitch of some kind of oscillation. I've wired up with all the mods described in the build PDF.

Any ideas what could be causing the issues?

[Taylor]

Finished mine today, but still some troubleshooting required.

I'm only getting a single repeat and the modulation doesn't work. The speed knob seems to control the pitch of some kind of oscillation. I've wired up with all the mods described in the build PDF.

Any ideas what could be causing the issues?

For the single repeat, this means your whole audio path is working, through the CMOS switches into the delay chip and through the output stage, but there is no feedback happening. Your problem will be in the parts right below the feedback pot, probably a solder joint that needs to be reflowed, or possibly a wrong (too large) value for the 20k resistor there.

For the modulation, if moving the speed pot has an effect on the sound, that means the link from the modulation section to the delay chip is good, but your LFO isn't oscillating. This involves the parts on the right side of the board around the right TL072. Since you have all the mods, maybe your LFO switch pads are shorted together, or a short across your switch contacts, which would stop the LFO.

[Fine Mechanics]

Finished mine today, but still some troubleshooting required.

I'm only getting a single repeat and the modulation doesn't work. The speed knob seems to control the pitch of some kind of oscillation. I've wired up with all the mods described in the build PDF.

Any ideas what could be causing the issues?

For the single repeat, this means your whole audio path is working, through the CMOS switches into the delay chip and through the output stage, but there is no feedback happening. Your problem will be in the parts right below the feedback pot, probably a solder joint that needs to be reflowed, or possibly a wrong (too large) value for the 20k resistor there.

For the modulation, if moving the speed pot has an effect on the sound, that means the link from the modulation section to the delay chip is good, but your LFO isn't oscillating. This involves the parts on the right side of the board around the right TL072. Since you have all the mods, maybe your LFO switch pads are shorted together, or a short across your switch contacts, which would stop the LFO.

Many thanks again for the support, Taylor.

The feedback issue was an error on my part - I'd misread the instructions for the dub mod and had omitted the 20k resistor below the feedback pot from the board. After fitting the resistor the delay (without LFO) works as expected and sounds amazing.

The issue with the LFO persists however. When the LFO switch is in the 'on' position there is no modulation and there's a faint high pitched tone/oscillating/whining sound. The LFO speed knob alters the pitch of this sound. The LFO Depth knob alters the delay time slightly (suggesting that the problem isn't with the transistor) and the wave shape knob doesn't change the sound at all. The LED flickers briefly when the LFO switch is used but does not pulse with the speed of the modulation.

I can't see any shorts and have reflowed all the joints to the right hand side of the board and LFO related pots.

Any advice regarding where next to direct troubleshooting efforts would be greatly appreciated!!

[Taylor]

So, the LFO's not oscillating. Could be something funky with the 1uf cap above that rightmost TL072? It needs to be a non-polarized part, what kind of cap do you have there? Does anything change between the two settings of the LFO switch?

[Fine Mechanics]

So, the LFO's not oscillating. Could be something funky with the 1uf cap above that rightmost TL072? It needs to be a non-polarized part, what kind of cap do you have there? Does anything change between the two settings of the LFO switch?

Thanks again Taylor. The cap is a non polarised film type as per the build spec. After removing the  TL72, reheating all relevant joints in the area and re-inserting the chip all is now working and sounds great! I love it! Will be sure to post pics and maybe a video in a couple of weeks once I've gotten round to painting the enclosure.

Initial thoughts are that the delay sounds quite overdriven in a Memory Man kind of way, which I absoloutely love, but can see why certain players would comment that the repeats aren't as clean as expected.  Oscillation sounds awesome; way better the in any of the video demos I've seen. Wave shape mod is awesome, unlocking almost a faux sequencer type quality, dub mod is cool, diode lift doesn't make a huge difference but I've only played for a few minutes at low volume.

Further mods that I'll be including will be exp control of feedback and maybe a momentary footswich for dub madness.
 
Thirst for a Moog delay is now quenched. For the time being, at least!

[Granny Gremlin]

Hi guys, new here, was having some problems with my Echo base build (1st of 2 - building one for me and one for a bud) and was about to post a question but it looks like this here might be (part of) my problem:

Finished mine today, but still some troubleshooting required.

I'm only getting a single repeat ...

Any ideas what could be causing the issues?

For the single repeat, this means your whole audio path is working, through the CMOS switches into the delay chip and through the output stage, but there is no feedback happening. Your problem will be in the parts right below the feedback pot, probably a solder joint that needs to be reflowed, or possibly a wrong (too large) value for the 20k resistor there. ...

Many thanks again for the support, Taylor.

The feedback issue was an error on my part - I'd misread the instructions for the dub mod and had omitted the 20k resistor below the feedback pot from the board. After fitting the resistor the delay (without LFO) works as expected and sounds amazing.

So I do not have this resistor populated either so that's def my issue (kicking myself because as I was wiring up my momentary  switch assembly I totally noticed that I read the build doc wrong too but then forgot).  thanks.

The mods I have included are:
- modulation shape - no workie
- dub madness - works (momentary footswitch - love this! even without the feedback knob working properly the oscillation works and sounds brilliant; neat warpage sounds if you tweak the delay time knob while engaged)
- clean kill - works


With the single repeat I can't quite tell if the modulation overall is working; leaning to not.  I definitely do not hear any change when I crank the wave shape knob back and forth.  I originally thought that I buggered the wave shape mod (when the wave shape pot it all the way counter-clockwise the LED goes out; it flashes a bit as you turn it up and then remains solid 1/3 clockwise and up), but probably I just don't have the modulation working at all.  Once I fix the feedback and have more repeats it will be easier to tell.

Even if the modulation isn't working at all, it may not be for the same reason as Fine Mechanics as I am not getting that weird noise that changes pitch with the speed knob.  Or maybe that's because I have the wave shape mod but he doesn't (?)  What I do see is that when the effect is on (no matter if LFO is on or off IIRC, but I will have to double-check that) I have what seems to be excessive noise.  More than there should be; I am not expecting this to be dead quiet.

Anyway, I'll try fixing the feedback and check some of the other things Taylor mentioned to FM to look at and see if I can figure out the modulation issue. So, uh, thanks for the help; I'll come back if I can't sort it out.

[Granny Gremlin]

I got the feedback working so I have multiple repeats now.  Got rid of a significant chunk of the noise by tracking down a resistor shorting to ground (shape mod; 240K to pot chassis).  Modulation is definitely not working - haven't figured that out yet but only gave it a quick look.  That large film cap is not the problem though.  The 72 in the modulation section looks a bit crooked in it's socket so I think I'll try re-socketting that  first in case there's a leg that's not making contact or something, heck even sub in another one just to be sure I didn't burn it somehow.