Another Stupid Question??? (TL072 Op-Amp)

[WLS]

Let me start off by asking another stupid question.

Shouldn't an Op-Amp TL072 give off sound through it's output. The reason why I ask is that I am bread boarding the PT-80 and finished putting it together. Went over it twice and then tested it and got light off the jFET but nothing else. Using an audio probe I started to trace with my audioline and got to the first item after the input.

The TL072 Op-Amp is dead! 

It has sound going to the Input pin but nothing coming out the output. Only if I turn my amp up that I can vaguely here the instrument. The TL072 Op-Amp has 12 volts going to it and the ground is connected.

Any Ideas!

[WLS]

Just got away from the wife long enough to get some voltages on the IC:

Pin-1    1.7
Pin-2    1.2
Pin-3    .2
Pin-4    Ground
Pin-5    0
Pin-6    4.5
Pin-7    9.2
Pin-8    12

I was reading something about LFO for this device and that their should be fluctuations on voltages for the output Pins 1 and 7. Being new at this I am not sure as to what this refers too and I can not find anything in the data sheet in regards to this.

Question: Does it matter which side of the IC is used as input. My Input is based off of side 1 Thur 3 pinset?

               Does LFO stand for Last in First Out it seems that all my voltage is towards one side of the chip?

The Schematic is off GGG's Sight and can be viewed at http://www.generalguitargadgets.com/diagrams/pt80schem.pdf

Sorry for the delay in posting the rest of the specs any assistance is greatly appreciated.

Thank You!

[km-r]

pins 3 and 5 should be about 6v. but if youre using a analog vom, the vom will load up the bias and will give off a wrong measurement.
the output pins 1 and 7 should be 6v in the vom whether analog or digital.

[WLS]

I am using a analog VOM have a new digital on order but has not showed up yet.

Thanks for the bench mark!

[km-r]

bias issues are always a pain in the ***... anyway, just make sure the "R" voltage is half the supply voltage then make sure the 1M resistors are OK.

[anchovie]

LFO stands for Low Frequency Oscillator. There isn't an LFO in the PT-80 circuit.

The PT-80 is a very complex circuit to have on a breadboard. Your op-amp isn't necessarily dead, there's just a good chance that things aren't connected to it correctly. The obvious thing is to try another op-amp in there to confirm or deny this.

As you've stated in some of your earlier posts that you're new to electronics and ICs, I would strongly suggest that you pick a single-chip distortion or overdrive to set up on your breadboard and experiment with so you can get a feel for how the inputs, outputs and feedback loops hook up in a circuit. Best not to race ahead too quickly when there's so much to learn!

If you really want a PT-80, order the board from GGG. I built one last week and it worked first time.

[GibsonGM]

...especially since there's a decent shot at ruining those expensive chips!  Save 'em for a few months from now when you've gained the experience to assemble the stuff correctly and will lessen the risk of blowing things up that cost $$ to replace...
No such thing as a stupid question, there are only "noob" questions 

[WLS]

Well, I reworked the power supply where I found the area with the two 10k resistors and the polarized cap just wasn't correct (resistor to ground pin off a row and not connecting to the polarized cap). Had a 1m resistor leading into the Op-Amp going to ground instead of the power source and tweaked some wires.

The benchmarks for the TL-072 along when rereading the data sheet helped a lot. It finally clicked as to what was on the data sheet in regards to the pins should be half the input voltage. Thanks to km-8 for that piece of information.

Anyway's I got the voltages to the Op-Amp looking pretty good.

They are now showing:

1.  .3     Low due to 1m pulldown resistor.
2.  4.9   Ok!
3.  4.9   Ok!
4.  0      Ground Ok!
5.  4.6   Ok!
6.  4.9   Ok!
7.  4.9   Ok!
8.  9.4   Ok!

Plugged everything in and still know sound. So, I pulled out the audio probe and found the Op-Amp to be function properly. And now my problem is laying at the next IC the SA-571. I have sound up to the IC, but nothing on it's outputs.

The Voltages for the SA-571 are as follows:

1.  0     Rec. Cap. #1
2.  1.8   Rec. In #1
3.  1.8   AG Cell #1
4.  0     VCC (-)
5.  2     Inv. In #1
6.  6.6   Res. R3 #1
7.  6.6   Output #1
8.  1.9  Thd. Trim #1
9.  1.9    Thd. Trim  #2
10.  8.6   Output #2
11.  .7     Res. R3 #2
12.  1.3   Inv. In
13.  9.4   VCC (+)
14.  1.5   AG Cell R3 #2
15.  1.5   Rec. In #2
16.  0      Rec. Cap. #2

Thanks to anch for the definition of LFO and the information that this circuit does not contain a Low Frequency Oscillator.

As far as knowing what I want from a box I am not sure  that's why I am breadboarding the project. I have just purchased 3 SADA1024A's. It seemed to be the last three on the planet by how hard they where to obtain I guess that is the bases of the next one I will put to solder. As soon as I become skilled enough to build a project of that caliber. But a project like this is how I learn.

Any More Assistance and Benchmarks Would Be of Great Help.

Suggestions Greatly Appreciated.

Thanks to Everyone!

[anchovie]

Anyway's I got the voltages to the Op-Amp looking pretty good.

They are now showing:

1.  .3     Low due to 1m pulldown resistor.

That's doesn't make sense. The schematic doesn't show a 1M pulldown resistor on either of the op-amp outputs. They both have 1uF coupling capacitors and the output of the first op-amp also splits off to the 10k resistor on the inverting input of the second op-amp.

[WLS]

That's doesn't make sense. The schematic doesn't show a 1M pulldown resistor on either of the Op-Amp outputs. They both have 1uF coupling capacitors and the output of the first Op-Amp also splits off to the 10k resistor on the inverting input of the second Op-Amp.

Maybe it is not called a pulldown resistor and for that I am wrong but on the schematic by the input jack on the positive input line going to the Op-Amp it starts with a compactor with a value of .047 and Right after that is a 1m resistor right before the line enters into the Op-Amp. The 1m resistor connects to R the 12v regulator with the two 1k resistors and 100uf polarized cap. (12 Volt running through the resistor only provides .3 volts). Then the other side of the Op-Amp has an output line going to the J201 and this side right after the Op-Amp does have a 1uf Cap. as you said followed by a 1m resistor to ground. Both sides of the Op-Amp have 1M resistors in use. GGG's Bill of Materials for the project also calls for two 1m resistors and this is thier placement.

Anyways, this might just be one of my major problems as I LOOK AT THIS! and please correct me if I am wrong. But I have the rings of both jacks going to ground and the tip of the input starting at the front of the .047 capacitor on the input line going into the Op-Amp and the output tip connecting into the output line in between the 1m resistor and the J201.

Both (A's) are connected by wire for cross over creating what I think by looking at the examples in the data sheet is an inverting amp that is being used here.

Anyways at this point the Op-Amp is functioning by passing sound through it but I still am not getting sound through the output jack. And the last time I probed I got as far as the SA-571 pin 11 with sound then dead from that point on. I worked all evening on this and checked it quickly with the jacks pluged in but still nothing I think I am getting closer but it is to late to start probing.

Don't need to wake the wife up! 

Like I have said before any assistance will be greatly appreciated.

I will update tomarrow where the project stands and thank you so kindly for your comments.   

[anchovie]

Check the datasheet for the TL072 - pin 1 is the output, which is why I questioned the 1M resistor.

Point R is not the 12v regulator, it is the point between the two resistors that run in series from the regulator to ground. The purpose of this is to act as a voltage divider, so with the two resistors being equal the point R should read 6v.

Another thing I need to check with you - you mentioned one of the op-amp outputs going to a J201: are you aware that the part of the schematic just before the output jack is a switch? (the three dots in a triangle shape with only one side drawn) The J201 is used to toggle the effect status LED and is not part of the audio signal, the effect would be connected to the output jack when the switch is in the opposite position.

I still think you should start with simpler circuits on your breadboard, you'll learn a lot more and see how small circuits can become "building blocks" in more complex ones. The PT-80 is not a great introduction - it's got the regulated power supplies, FET switching for an LED and because it's a delay the signal path is not simply one route from input to output. Like I said before, if you have a go at something that only has one or two op-amps (plus only runs off one battery and doesn't have anything to do with the status LED on the schematic as that would be handled by the footswitch) then that will give you a much better idea of exactly what you should be seeing on each pin of a correctly set up op-amp.

[WLS]

Point R is not the 12v regulator, it is the point between the two resistors that run in series from the regulator to ground. The purpose of this is to act as a voltage divider, so with the two resistors being equal the point R should read 6v.

Another thing I need to check with you - you mentioned one of the op-amp outputs going to a J201: are you aware that the part of the schematic just before the output jack is a switch? (the three dots in a triangle shape with only one side drawn) The J201 is used to toggle the effect status LED and is not part of the audio signal, the effect would be connected to the output jack when the switch is in the opposite position.

I have the regulators setup correctly on the board just a little hard to describe, but I feel real stupid now that I see what you are saying about the J-201 JFET not being tied into the audio line. The only time it will tie into the line is when the effect is off for grounding the board out I should have caught this because the FTM that I built grounds the board out through the switch also. Thank you very much for pointing that out to me!!! 

So, I disconnected the line from the JFET and I got sound through the jacks.

Problem at this point is know effect and I the only thing that I had just noticed in comparison of the schematic and GGG's component placement sheet is, that on the IC PT-2399 at pins 4, 5 & 6 for the delay time. The Schematic is showing 5 is open no connection. But on GGG's board layout for component placement it shows a trace that bridgeds together Pins 4 & 5. I do not have this done on my breadboard and the schematic does not show it. 

Pin 7 at this point shows no voltage myabe it will if I birdge Pins 4 & 5 and another concern is Pin 1 on the SA-571 with a zero voltage. I'll have to look at it closer but maybe thier all tied together.

Is their a place to get more information on the PT-2399? The data sheet I have does not provide hardly any information besides two examples and Pin assignment.

Afar as scrubbing the project at this point I feel I am very close to achieving results and I am learning from it.

Anyways the PT-80 project voltages at this point are as follows:

2N5088
Emitter 5.2V, Base 1V, Collector 12V

TL-072

Pin-1    6      Out #1
Pin-2    6     (-) IN #1
Pin-3   .3     (+) IN #1
Pin-4    0      VCC (-)
Pin-5    6     (+) IN #2
Pin-6    6     (-) IN #1
Pin-7    6      Out #1
Pin-8   12     VCC (+)


SA-571

Pin-1     0        Rec Cap #1           Pin-9       2       THD Trim #2
Pin-2     1.6     Rec In #1              Pin-10     6       Output #2
Pin-3     1.6     AG Cell #1             Pin-11     1       Res R3 #2
Pin-4     0        VCC (-)                 Pin-12     1.8     Inv, IN #2
Pin-5     2        Inv, IN #1             Pin-13     12     VCC (+)
Pin-6     6.5     Res R3 #1             Pin-14     1.6    AG Cell #2
Pin-7     6.5     Output #1             Pin-15     1.6     Rec In #2
Pin-8     2        THD Trim #1        Pin-16     1.2     Rec Cap #2


PT-2399

Pin-1     5        VCC           Pin-9       2.6       OP1-OUT
Pin-2     2.4     REF            Pin-10     2.6       OP1-IN
Pin-3     0        AGND         Pin-11     2.6       OP2-IN
Pin-4     0        DGND         Pin-12     2.6       OP2-OUT
Pin-5     4        CLK_0        Pin-13     2          LPF2-IN
Pin-6     2.6     VCO           Pin-14     2.6       LPF2-OUT
Pin-7     0        CC1           Pin-15     2.6       LPF1-OUT
Pin-8     1        CCO          Pin-16     2          LPF1-IN


I do sincerely thank you for your help.

Thank you very much for your input.

[WLS]

Problem at this point is know effect and I the only thing that I had just noticed in comparison of the schematic and GGG's component placement sheet is, that on the IC PT-2399 at pins 4, 5 & 6 for the delay time. The Schematic is showing 5 is open no connection. But on GGG's board layout for component placement it shows a trace that bridgeds together Pins 4 & 5. I do not have this done on my breadboard and the schematic does not show it. 

Pin 7 at this point shows no voltage myabe it will if I birdge Pins 4 & 5 ... 

Sorry, retraction!

PT-2399 Pins Are not bridge at 4 & 5 it  is 3 & 4 on GGG's Component Placement Sheet!

The glockoma is acting up today.

I apologize for the incorrect information.

[anchovie]

Time to trace through with the audio probe again.

[WLS]

I am going to flip the SA-571 first to check if it's bad.

Last night I made a device out of some parts that will flip the sides of mirrored IC chips so that I can check the operation of the chip using the voltages of one side aginst the other with out disturbing any other components.

If the voltages match then everthing is ok with the chip.

If not, then blown chip RIGHT!

If the chip is blown and I put back to it's orriginal orentation and the voltages changed then something is still wrong to the point it will blow the new chip when inserted into the board.

You would have nothing too lose but what would already be a blown chip.

Thanks!

[WLS]

Just finished testing the chip and I blew it all a part of the learning process! Put in a new chip and just started using a digital multimeter NICE... Made a few changes and plugged it in using the jacks and still know effect. Got out the probe and tested pins 7 and 10 on the SA-571 (Outputs) and this time their was sound coming out of them.

If I'm right then this would mean that at least I have a functional signal from the SA-571 through the one bank of the PT-2399 and back again?

But why would their be no effect???

Anyways here is the new voltages: 

TL-072

Pin-1    5.41      Out #1
Pin-2    5.40     (-) IN #1
Pin-3    4 .81    (+) IN #1
Pin-4    0          VCC (-)
Pin-5    5.35     (+) IN #2
Pin-6    5.35     (-) IN #2
Pin-7    5.33      Out #2
Pin-8    10.76    VCC(+)

Pin-1     .31     Rec Cap #1         Pin-9       1.78    THD Trim #2
Pin-2     1.78   Rec In #1            Pin-10     5.98    Output #2
Pin-3     1.78   AG Cell #1           Pin-11     1.78    Res R3 #2
Pin-4     0        VCC (-)               Pin-12     1.78    Inv, IN #2
Pin-5     1.78    Inv, IN #1           Pin-13    10.68   VCC (+)
Pin-6     6.6     Res R3 #1           Pin-14     1.78    AG Cell #2
Pin-7     6.6     Output #1            Pin-15     1.78    Rec In #2
Pin-8     1.78   THD Trim #1        Pin-16     1.27    Rec Cap #2


PT-2399

Pin-1     5.04   VCC           Pin-9       2.52      OP1-OUT
Pin-2     2.52   REF           Pin-10     2. 52      OP1-IN
Pin-3     0        AGND        Pin-11     2. 52      OP2-IN
Pin-4     0        DGND        Pin-12     2.52       OP2-OUT
Pin-5     4.31   CLK_0        Pin-13     2.52       LPF2-IN
Pin-6     2.5     VCO          Pin-14      2.52      LPF2-OUT
Pin-7     .88     CC1           Pin-15      2. 52     LPF1-OUT
Pin-8     .88     CCO          Pin-16      2. 52      LPF1-IN


Thank You!

[WLS]

Well, after a week of pulling my hair out, a few posts, some help from the good people on this forum, and still trying to use a pot that I should have thrown away. I can finally say...

WHOW IT SOUNDS AS WILD AS IT LOOKS!!!   

I would like to thank everyone for their thought and assistance. This is a project that was trying for me and I would like to say that I learned a great deal from it. My thoughts are to later add a second PT-2399 Chip to the board to go more towards the ability of a chorus effect.

Finished Product:




In an effort to give back here are the voltages for all the components in the PT-80 with a charge pump being used in conjunction with a 9V Battery.

Alterations: The TC1044SCPA was used instead of the MAX1044. Low Impendence Alumn Electro Polor Caps, 1N4002 Rectifiers, the 1uf are box capacitors the pf caps are monolithic, a J-201 JFET with a super bright LED and a 2n5087 Transistor.

Anyways here are the voltages:

2N5087                                     J-201
10.85   Collector                        10.47   Drain
5.22    Base                             10.43   Source
4.73    Emitter                          10.96   Gate


TL-072CP

Pin-1    5.37      Out #1
Pin-2    5.36     (-) IN #1
Pin-3    4 .77    (+) IN #1
Pin-4    0          VCC (-)
Pin-5    5.31     (+) IN #2
Pin-6    5.32     (-) IN #2
Pin-7    5.32      Out #2
Pin-8   10.67    VCC(+)


SA-571IN

Pin-1     .72     Rec Cap #1           Pin-9       1.78   THD Trim #2
Pin-2     1.78   Rec In #1              Pin-10     5.94   Output #2
Pin-3     1.78   AG Cell #1             Pin-11     1.78    Res R3 #2
Pin-4     0        VCC (-)                  Pin-12     1.78    Inv, IN #2
Pin-5     1.78    Inv, IN #1            Pin-13    10.51  VCC (+)
Pin-6     6.64     Res R3 #1           Pin-14     1.78    AG Cell #2
Pin-7     6.64     Output #1           Pin-15     1.78    Rec In #2
Pin-8     1.78   THD Trim #1          Pin-16     1.22    Rec Cap #2


PT-2399

Pin-1     5.03   VCC           Pin-9       2.52       OP1-OUT
Pin-2     2.51    REF           Pin-10     2. 52      OP1-IN
Pin-3     0        AGND         Pin-11     2. 52      OP2-IN
Pin-4     0        DGND         Pin-12     2.52       OP2-OUT
Pin-5     4.68   CLK_0        Pin-13     2.52       LPF2-IN
Pin-6     2.51     VCO         Pin-14     2.52       LPF2-OUT
Pin-7     .82     CC1           Pin-15     2. 52       LPF1-OUT
Pin-8     .82     CCO          Pin-16     2. 52       LPF1-IN


Hope these bench make helps someone else at a later point in time!

Again thanks to everyone for their assistance any comments about this project or suggestions are always welcome.