Equinox II breadboard issues

[jfrabat]

I decided to give a reverb a go (I did have some PT2399s around), and went with this design.

http://www.valvewizard.co.uk/equinox.html

I used the schematic on the PDF as a guide (have not checked to make sure it is the same as in the page, but I guess it is!).  Anyway, sound IS coming through, but it is heavily clipped and VERY muddy (not sure if there is any reverb). 

Changes I have made:
1. JFET is 2N5457 instead of J112
2. C14 (calls for 1 to 10uF Tantalum; I had 15uF tantalum, so I have that in; I could change it to a 1 or 10uF electrolytic)
3. R1 (I did not have 10M resistors, so I used 2 X 4.7M in series)
4. C7 and C27 are 1uF brownies (it says non-polarized in the description)
5. Since it is in breadboard, I just jumpered FSb with FSa (no switch yet)

Voltages:
DC Jack: 9.37V
9V Rail: 8.58V
5V rail: 5.06V
4.5V Rail: 4.20V

Q1 (2N5457)
D: 1.269V
S: 1.346V
G: 0V

U1 (TL072):
1: 7.36V
2: 4.22V
3. 4.21V
4: 0V
5: 0.983V
6: 1.338V
7: 1.338V
8: 8.56V

U2 (PT2399):
1: 5.06V
2: 2.52V
3. 0V
4: 0V
5: 3.61V
6: 2.49V
7: 0.665V
8: 0.693V
9: 2.52V
10: 2.52V
11: 2.52V
12: 2.52V
13: 2.52V
14: 2.52V
15: 2.52V
16: 2.52V

U3 (PT2399):
1: 5.06V
2: 2.52V
3. 0V
4: 0V
5: 3.77V
6: 2.51V
7: 0.594V
8: 0.611V
9: 2.52V
10: 2.52V
11: 2.52V
12: 2.52V
13: 5.04V
14: 3.22V
15: 2.52V
16: 2.52V

I have checked the schematic 3 times (WARNING: I AM DYSLEXIC!) and have not found any errors. 

[anotherjim]

It isn't clear which halves of the TL072 are which amps in the circuit. Something is wrong there though, Pins 3 and 5 should both have the 4.5v reference voltage and pins 1 and 7 should do too. The amp at the input gets the reference via 1M so your meter input impedance will make that read lower. Make sure the coupling caps on the opamp inputs are good/present.
The PT2399 readings seem normal.
If you doubt the JFET, it can be removed and a wire fitted between the source-drain so that it's always on.

[jfrabat]

It isn't clear which halves of the TL072 are which amps in the circuit.

In the PDF, it clearly labels the pin numbers.  U1-B is the first amp (pins 5, 6, and 7).

Something is wrong there though, Pins 3 and 5 should both have the 4.5v reference voltage and pins 1 and 7 should do too.  The amp at the input gets the reference via 1M so your meter input impedance will make that read lower.

Educate me a bit; I can clearly undestand why pin 3 would have 4.5V (in this case, 4.2V, which is what the 4.5V rail is actually reading), but why would pin 5 have it, if it is coming from the line input?

Make sure the coupling caps on the opamp inputs are good/present.
The PT2399 readings seem normal.
If you doubt the JFET, it can be removed and a wire fitted between the source-drain so that it's always on.

In this case, C1 would be the coupling cap, right?  All caps are there as per the schematic...  I will try jumping the JFET and see if that helps.

[duck_arse]

Q1 (2N5457)
D: 1.269V
S: 1.346V
G: 0V

U1 (TL072):
1: 7.36V
2: 4.22V
3. 4.21V
4: 0V
5: 0.983V
6: 1.338V
7: 1.338V
8: 8.56V

U2 (PT2399):
1: 5.06V
2: 2.52V
3. 0V
4: 0V
5: 3.61V
6: 2.49V
7: 0.665V
8: 0.693V
9: 2.52V
10: 2.52V
11: 2.52V
12: 2.52V
13: 2.52V
14: 2.52V
15: 2.52V
16: 2.52V

U3 (PT2399):
1: 5.06V
2: 2.52V
3. 0V
4: 0V
5: 3.77V
6: 2.51V
7: 0.594V
8: 0.611V
9: 2.52V
10: 2.52V
11: 2.52V
12: 2.52V
13: 5.04V << these two points should be shorted together
14: 3.22V << and both about 2V5
15: 2.52V
16: 2.52V

I have checked the schematic 3 times (WARNING: I AM DYSLEXIC!) and have not found any errors.

photos of your build breadboard, please! (same rules apply.)

my circuit diagram also has no pin numbers - but pins 3 and 5 are the non-inverting inputs, no? when they are told to be 4V5, they set the output pins [1 and 7, no?] to be 4V5 as well, no arguments.

so your TL072 pin 1 should be 4V22, cause you told it to be. the other half of the IC, connecting to the fet, has all wrong volts, input and output.

[jfrabat]

photos of your build breadboard, please! (same rules apply.)

Sure, here you go:

my circuit diagram also has no pin numbers - but pins 3 and 5 are the non-inverting inputs, no? when they are told to be 4V5, they set the output pins [1 and 7, no?] to be 4V5 as well, no arguments.

OK, have some patience with me...  Still a noob and not yet understand completely...  Here is the schematic I am following (from Valve Wizard's site):



I can clearly see how pin 3 is 4.5V and why the output would be affected (pin 1).  But I do not see how the second amp gets 4.5V at Pin 5.  Education is highly appreciated here!

U3 (PT2399):
1: 5.06V
2: 2.52V
3. 0V
4: 0V
5: 3.77V
6: 2.51V
7: 0.594V
8: 0.611V
9: 2.52V
10: 2.52V
11: 2.52V
12: 2.52V
13: 5.04V << these two points should be shorted together
14: 3.22V << and both about 2V5
15: 2.52V
16: 2.52V

the other half of the IC, connecting to the fet, has all wrong volts, input and output.

Yeah, that is the part I do not get.  I pretty much can determine the voltages are wrong, but I still do not understand why they are wrong...  I am stumped.  Must be a short somewhere, I guess, but I cannot find it!

[PRR]

> I do not see how the second amp gets 4.5V at Pin 5.

R3.

[jfrabat]

> I do not see how the second amp gets 4.5V at Pin 5.

R3.

Ah...  It goes to 4.5V!  I have it to ground!  NO WONDER! 

[jfrabat]

Dry signal is now cristal clear.  But no reverb.  Will post voltages later.

[jfrabat]

New voltages:
DC Jack: 9.43V
9V Rail: 8.61V
5V rail: 5.06V
4.5V Rail: 4.22V

Q1 (2N5457)
D: 3.82V
S: 4.04V
G: 0V

U1 (TL072):
1: 5.23V
2: 4.24V
3. 4.23V
4: 0V
5: 1V to 2.6V
6: 4.03V
7: 4.04V
8: 8.61V

U2 (PT2399):
1: 5.06V
2: 2.52V
3. 0V
4: 0V
5: 3.61V
6: 2.49V
7: 1.12V to 1.17V
8: 1.04V to 1.17V
9: 2.52V
10: 2.52V
11: 2.52V
12: 2.52V
13: 2.52V
14: 2.52V
15: 2.52V
16: 2.52V

U3 (PT2399):
1: 5.06V
2: 2.52V
3. 0V
4: 0V
5: 3.77V
6: 2.51V
7: 1.13V to 1.16V
8: 1.13V to 1.19V
9: 2.52V
10: 2.52V
11: 2.52V
12: 2.52V
13: 0.462V Still issues here
14: 5.04V Still issues here
15: 2.52V
16: 2.52V

[anotherjim]

U3 pins 13 & 14 are an unused op-amp in the PT2399. A wire link shorts them together so that amp won't cause interference. There shouldn't be any difference in voltage between those pins. You may have bent a pin under the PT2399 and so not got a connection.
In my last reply, I said...
"The amp at the input gets the reference via 1M".
So do you see how pin 5 gets 4.5v?

[bluebunny]

Watch this: https://youtu.be/7FYHt5XviKc

It is pretty much required viewing.  It will reveal all the secrets of opamps and will make clear the answers to your questions about the voltages on those pins.

[merlinb]

Dry signal is now cristal clear.  But no reverb.

Remove Q1 to start with, it's for the footswitching which you don't really need right now. Replace it with a wire link.

[cab42]

Watch this: https://youtu.be/7FYHt5XviKc

It is pretty much required viewing.  It will reveal all the secrets of opamps and will make clear the answers to your questions about the voltages on those pins.

Thats a great ressource. Just watched the first half, between two online meetings. Looking forward to the second half.

[jfrabat]

Watch this: https://youtu.be/7FYHt5XviKc

It is pretty much required viewing.  It will reveal all the secrets of opamps and will make clear the answers to your questions about the voltages on those pins.

Excellent! Will watch it tonight

Dry signal is now cristal clear.  But no reverb.

Remove Q1 to start with, it's for the footswitching which you don't really need right now. Replace it with a wire link.

OK

U3 pins 13 & 14 are an unused op-amp in the PT2399. A wire link shorts them together so that amp won't cause interference. There shouldn't be any difference in voltage between those pins. You may have bent a pin under the PT2399 and so not got a connection.

I noticed I get 2.56V in Pin 14, but as soon as I measure pin 13, pin 14 raises to 5V

[duck_arse]

this won't fix anything now, but, your C5 fitted is 1nF [102] when it should be 10nF [103]. as anotherjim sez - power off, remove that IC, and look closely at its pins. please.

[jfrabat]

this won't fix anything now, but, your C5 fitted is 1nF [102] when it should be 10nF [103].

Done.  Not sure how that cap found itself in the wrong stash...

as anotherjim sez - power off, remove that IC, and look closely at its pins. please.

I changed the IC (U3) to a new PT2399, and same thing (there were no bent legs in the original, by the way)...  If I power up the pedal and measure pin 14, I get 2.74V.  If I measure 13 and then 14 again, it goes to 5V.

[jfrabat]

"The amp at the input gets the reference via 1M".
So do you see how pin 5 gets 4.5v?

Now I do, yes.

Watch this: https://youtu.be/7FYHt5XviKc

It is pretty much required viewing.  It will reveal all the secrets of opamps and will make clear the answers to your questions about the voltages on those pins.

That explains A LOT!!!  Just saw it now...

Now back to the pedal at hand.  Chasing down what AnotherJim mentioned, obviously something was wrong (or shorting) because I redid the lower part of the circuit (everything between C7 to pins 9~16) and now 5he voltages are correct (~2.5V) for pins 13 and 14.  But still no reverb.  I still need to remove Q1, though, and try that.  Will do it after a meeting....

[anotherjim]

Just to make things worse for you, you cannot trust breadboard contacts 100%.

The contacts are single pieces with a channel profile like an inverted omega sign. When you insert a component leg, it pushes open the jaws formed at the top. To some extent that partially opens the jaws on the adjacent pins (contact spreading). This means that a thick leg can cause a thinner leg next to it to lose contact. Some integrated circuits, in particular, have very thin legs so I always try to leave the first available hole next to it empty to reduce contact spreading.

If you have components supplied in gummed paper bandoliers, some gum remains on the legs. The gum can transfer into the breadboard contacts and cause connection problems.

Simple logic - if you have a wire (continuity) between 2 points, you cannot have different in voltage between those points. If you do have a difference, there cannot be a connection.