Echo Blue (Deep Blue Delay) voltages issue

[khm9]

Hi all,
I finished populating Echo Blue PCB I got from pedalparts.co.uk ( http://pedalparts.co.uk/docs/EchoBlue-v3.pdf ).
I soldered every part very carefully and checked for shorts multiple times before soldering pots onto the PCB.

Before connecting the battery I checked it's voltage, 8.76V, after connecting it, it dropped to 5.90V and I also checked if there is any connectivity between v and g on the PCB, and there was, it was beeping like there was a short, that should not happen right?

Then I proceeded to check the voltages on the IC's, got very odd results,

IC1 (TL072)
0.08 -- 0.78
0.66 -- 0.14
0.66 -- 0.14
0.00 -- 0.00

IC2 (PT2399)

0.42 -- 0.10
0.21 -- 0.08
0.00 -- 0.16
0.00 -- 0.13
0.09 -- 0.13
0.00 -- 0.11
0.03 -- 0.04
0.03 -- 0.04

IC3 (L78L05)
0.39
0
0.76

After I did this, I checked the voltage between the v and g again, and it dropped to just a bit below 3V. After I disconnected the battery I checked its voltage and it was 7.76V.
All components except the elec caps and the trimmer were bought from Tayda.
I haven't attempted connecting it to the amplifier due to the weird voltages.

Schematic:




PCB I finished:




I really do not know how to debug this build, first thought that came on my mind were the IC's from Tayda, which I think are not genuine.

If you had any similar experience with your builds, share your solutions or any help on how to debug this build is much appreciated! 

[Kipper4]

Did the battery get hot?
I dont get why you have no +9v anywhere on the pcb.
Is Diode D1 oreintated right?
Your battery sure drained fast.......

Make sure you check the pinout and double check the pinout of the voltage regulator (IC3) 78L05.
Some data sheets show the package from below. Which in my experience is not the norm.


I've bought pt2339 from Tayda and not had any problems so far and TL072s too.

[khm9]

Did the battery get hot?
I dont get why you have no +9v anywhere on the pcb.
Is Diode D1 oreintated right?
Your battery sure drained fast.......

Make sure you check the pinout and double check the pinout of the voltage regulator (IC3) 78L05.
Some data sheets show the package from below. Which in my experience is not the norm.


I've bought pt2339 from Tayda and not had any problems so far and TL072s too.

No battery did not get hot, "v" on the pcb is +9v, diode is oriented correctly, cathode in the square spot. (from pdf: Striped end of the diode goes into the square pad).
I know delay circuits eat batteries fast, but can it really eat a battery in less than 3 mins?

[Kipper4]

I thought if the reverse polarity protection diode D1 was back to front it would short the power supply. but then the battery would get hot very quickly.

The pt2399 is a digital chip and will eat batterys but not within minutes surely.

[khm9]

I thought if the reverse polarity protection diode D1 was back to front it would short the power supply. but then the battery would get hot very quickly.

The pt2399 is a digital chip and will eat batterys but not within minutes surely.

I just checked the diode with a multimeter, and it shows readings when probes are put both correctly and incorrectly, and it should only show readings when they are put correctly right? Could it be that I fried the diode while soldering it?

[Kipper4]

What readng?
Forward voltage in diode mode?
Resistance?
Continuity ?


If in diode mode the meter should register a forward voltage of around a half volt? Mine usually say 0v7
Only one way?

Not trying to be funny.

You could always remove/replace the diode maybe.

Double check the power supply orientation. I only say this because I've made this gaff before.

[khm9]

What readng?
Forward voltage in diode mode?
Resistance?
Continuity ?


If in diode mode the meter should register a forward voltage of around a half volt? Mine usually say 0v7
Only one way?

Not trying to be funny.

You could always remove/replace the diode maybe.

Double check the power supply orientation. I only say this because I've made this gaff before.

I was reading in diode mode, continuity, it showed a reading of .500 when placed correctly and .1600 when placed incorrectly.

Anyway,
I replaced the diode, took a new battery, and got some new incredible results that to my eyes look like they could be correct

Battery: 9.5v

IC1
1: 3.77 - 5: 7.13
2: 3.74 - 6: 3.48
3: 3.69 - 7: 3.38
4: 0.00 - 8: 3.21

IC2
1: 4.54 - 9: 2.45
2: 2.18 - 10: 2.45
3: 0.00 - 11: 2.45
4: 0.00 - 12: 2.45
5: 2.39 - 13: 2.45
6: 2.10 - 14: 2.45
7: 0.62 - 15: 2.45
8: 0.64 - 16: 2.45

IC3
1: 5.53
2: 0.00
3: 4.18

Battery after disconnecting: 8.95v, there were no shorts between v and g anymore.
Only weird looking thing are the 9 - 16 voltages in IC2 which are all 2.45v.

What do you think?

[Kipper4]

I'm concerned about IC3
Pins should be +9v 5v 0v no?

I'll look up the rebote delay which I think is near enough the same circuit and its voltages.

[MrStab]

hi Khm,

is that definitely a new battery? is it a cheap one? i ask as it's being sagged considerably under load, as you'll notice from Pin 8 of IC1 (which you marked as pin 5. count em as though it's a smiley face!). also, that 4.5V from the 78x05 regulator seems a bit low to me - the datasheet says min. output should be 4.75V. i'd imagine any lower and you'll hit a voltage drop which won't meet the PT2399's needs.

PT2399 chips latch up a LOT, btw, i think due to counterfeits. shorting pins 3 and 4 of IC2 together is known to fix latch-ups a lot. afaik, those pins are connected by a 10-ohm resistor anyway, so it shouldn't affect the Delay pot. if that still doesn't work, you might wanna try a new PT2399.

[MrStab]

yeah IC3 is definitely wrong. what does IC3 read if you remove IC2?

[khm9]

I'm concerned about IC3
Pins should be +9v 5v 0v no?

I'll look up the rebote delay which I think is near enough the same circuit and its voltages.

I just checked again the voltages on IC3, I haven't written them correctly last time.
now,
1: 7.50
2: 0.00
3: 4.91

[khm9]

hi Khm,

is that definitely a new battery? is it a cheap one? i ask as it's being sagged considerably under load, as you'll notice from Pin 8 of IC1 (which you marked as pin 5. count em as though it's a smiley face!). also, that 4.5V from the 78x05 regulator seems a bit low to me - the datasheet says min. output should be 4.75V. i'd imagine any lower and you'll hit a voltage drop which won't meet the PT2399's needs.

PT2399 chips latch up a LOT, btw, i think due to counterfeits. shorting pins 3 and 4 of IC2 together is known to fix latch-ups a lot. afaik, those pins are connected by a 10-ohm resistor anyway, so it shouldn't affect the Delay pot. if that still doesn't work, you might wanna try a new PT2399.

Yes battery is new and it's a cheap one. I only use it for testing circuits, never had a problem. IC3, Vout, pin 1, is 7.50v, I wrote it wrong in a previous test.

[Kipper4]

These voltages are from a post on Madbeans.

here are my working voltages
     78L05
4.91 - top
0.00 - middle
9.01 - bottom

        TL072
4.5 - I--U--I- 9.02
4.5 - I       I- 4.5
4.5 - I       I- 4.5
0.0 - I ___ I- 4.5

      PT2399
4.9 - I--U--I- 2.4
2.5 - I       I- 2.4
0.0 - I       I- 2.4
0.0 - I       I- 2.4
0.0 - I       I- 2.4
2.4 - I       I- 2.4
0.0 - I       I- 2.4
0.0 - I ___ I- 2.4

[Kipper4]

See what I mean about the underside view of the IC

[khm9]

These voltages are from a post on Madbeans.

here are my working voltages
     78L05
4.91 - top
0.00 - middle
9.01 - bottom

        TL072
4.5 - I--U--I- 9.02
4.5 - I       I- 4.5
4.5 - I       I- 4.5
0.0 - I ___ I- 4.5

      PT2399
4.9 - I--U--I- 2.4
2.5 - I       I- 2.4
0.0 - I       I- 2.4
0.0 - I       I- 2.4
0.0 - I       I- 2.4
2.4 - I       I- 2.4
0.0 - I       I- 2.4
0.0 - I ___ I- 2.4

See what I mean about the underside view of the IC

Looks very close apart from:
IC3 pin 1 and the 9.02 pin on the IC1 where I have around 7.13.
Also on IC2 pin 5,7,8 are 0 where I have some readings there.

Since these are clones and schematics probably are a bit different, mine could be correct too.
I'll test the circuit tomorrow on an amplifier.

[Kipper4]

Good luck.

[khm9]

Good luck.

Thank you for all your help
I will post results tomorrow!

[MrStab]

don't get me wrong on the cheap battery thing - i use em often for simple circuits, but digital tends to drain em quickly. if the loaded voltage sinks below 7V or so, IC3 will no longer be able to output 5V.
hope you get it working!

[PRR]

I believe the PT2399 sucks FAR more current than a 9V battery can supply, even for minutes.

Can anybody else here run a PT2399 on a 9V battery long enough to play a song (or get a bunch of readings)?

[khm9]

Good day everyone,

I have tested the circuit on the amplifier, it works like it's supposed to.
But after few minutes of playing I heard one thing that I did not like and I doubt its the delays character.
Once delay starts repeating there is present some small hum on every repeat, when there are no repeats, there is no hum even if the guitar is still plugged in, so hum comes only with repeats  .

So could this be the non genuine PT2399 ?

edit: as i hit the strings harder, the hum becomes more noticable