Ross compressor clone wont work

[Demone]

Hi all,
thats my first post, I hoped to make it to show my work, but no way it'll be a looking-for-help one  :cry:

1. Ross Compressor clone

2. Schematic from: http://www.tonepad.com/getFile.asp?id=9

3. I followed the Tonepads layout exactly.

4. Changed tranz into 2N0588 and input cap to 100pf

5. Negative ground circuit... ya know

6. No sound at all

7. IC, Transistor and Diode readings following tonepad schematic naming battery is at 9.06 / 9.10 v is it possible that it obscillates
thats the reson why I get two values btw I think its not a battery fault

CA3080E
1 N.U.
2 4.68 / 4.71
3 4.68 / 4.71
4 0
5 6.66 <- thats strange ?
6 2.79 / 2.81
7 9.06
8 N.U.

Q1
C: 7.08
B: 2.36
E: 1.98

Q2
C: 6.73 / 6.77
B: 2.79 / 2.81
E: 2.27

Q3
C: 8.93
B: 0
E: 0

Q4
C: 8.93
B: 0
E: 0

Q5
C: 9.06
B: 8.93
E: 8.59

Everytime you see a / its because the value obscillates between the two values perfectly probably its the battery
From a post I'v read from Keen he said that it couldnt be that the pin5 of the IC has big values but I have.

Thats the monster wired up for testing...a short testing :?

[trjones1]

I just finished this myself, it's a nice build.  

My only questions are 1. Have you set the trimpot?  and 2. D1 looks like a different type than the other two.  All three should be the same.  I don't know if this would make the circuit nonfunctional, but it's worth checking out.

[SonicVI]

I'm thinking something is not right with Q3 and Q4.  Also 100pf is quite small for in input cap isn't it? I would think that would leave you with very little low end.

Also, it looks like you're using a switching jack for the output jack, and it looks like the wires might be on the wrong tabs?

[Demone]

@trjones1
Yes the trimpot is setted at a half with a volt meter.
The D1 is different, its from the fuzzcentral parts list, Philip from fuzzcentral used it too with no problems.

@SonicVI
You have a nice eye my friend, my problem is that I changed that :cry:
the photo shooted is before the changing and when I saw that inverting wires IT still didnt sound at all I thought to suicide.
What about the Q3 Q4 ?
I put values sidebyside with ones at fuzzcentral and yes I get them slightly different (that should be logical), the only one that is tremendously away is the 5th pin of the 3080.

btw I dont get a thing about electronics I'm a newbie, but I cant understand how having the Q5 emitter at 9.0v one could get 0.63v at the 5th pin of the IC only having a 27k resistor and a 500k pot between them.

[SonicVI]

I would think there should voltages on at least the bases of Q3 and Q4.

[tiges_ tendres]

have you tried changing the opamp?  Could be dead

[Demone]

I have two CA3080 and I just tried both with the same result.
Now it could be that everytime I put one it fries and gives that readings...

Is there any method to test the signal path ?

@SonicVI
I think I'v read somewhere that Q3 and Q4 are used here to something else than amplify.

[Demone]

I gave it a little more time today.
I plugged the guitar in the input, nothing in the output, sensitivity and level at 50% each put the voltmeter at 20v, the black voltmeter pen at ground and the red one at various points as to check voltages.
I'v noticed that it doesnt output anything... I mean I have 2.38v at the input of the .05 cap before the 10k res that is before the 50k output pot.
Understanding nothing about that stuff, I thought the .05 cap was broken and I replaced it, but the result was the same.
As I'm actually improvising blindly    is there a person kind enought to help me with first steps just to give me a kickstart ?

Thank you all

[R.G.]

Demone, you're quite perceptive. Pin 5 on a CA3080 can't possibly be at 6.6V when pin 4 is at 0V. Try reading that directly on the IC pin, not on a trace connected to it. Pin 5 is internally connected to a diode to pin 4, and if you put more than 1ma through that diode, it kills the chip. Perhaps before you power it up again, you might use your ohmmeter to measure the resistances between the IC pin right at the body and then into the PCB traces. It could be a bad socket pin, or a bum solder joint.

Q3 and Q4 read correctly with 0V on base and emitter since this is one of those funny circuits where they are completely off unless there is signal going through the circuit.

Those are the biggies. I think once you correct those, it might work.

[Demone]

Thank you very much Keen,
I'm actually taking values touching pins on the body of the chip because its simpler  
I took values like you told me and putting the scale @200ohm on the ohmmeter (this selection actually is the one that makes a sound when the two tips touch each other) and touching the pcb trace (I tried to avoid the solder block) the values is 0.05 for all pins of the IC.

As I said there is one thing I cant understand from top of my ignorance:
I'm just imagine that the pin 5 is the one that tells to the 3080 how much amplify (please tell me if I need to delete this post after that assertion) the problem is that if I'm actually giving it an 8.59 (with Q5 emitter) how can it go to 0.xx ?
Probably its a too long explanation for me just say that its possible and I'll shut up  :oops:
As soon as possible I'll get another 3080 at shop and try that.
The problem is that, as I just said, its possible that the circuit as its now will fry the new ic too  :roll:

[R.G.]

I'm just imagine that the pin 5 is the one that tells to the 3080 how much amplify (please tell me if I need to delete this post after that assertion) the problem is that if I'm actually giving it an 8.59 (with Q5 emitter) how can it go to 0.xx ?

No need to delet the post - it's dead accurate. Pin 5 is the pin that tells it how much to amplify; but it's the *current* that goes into pin 5 that controls the gain, not the voltage.

The problem is that, as I just said, its possible that the circuit as its now will fry the new ic too

Yeah, I hate the "sudden death" kinds of problems.  Here's how you prevent the sudden death. Your PCB should have a 27K resistor that's the only connection to pin 5. On the other side of that 27K resistor is the "compression" control, which is a pot to the emitter of Q5. That 27K resistor limits the current into pin 5 to less than 9V/27000 = 333uA even if the 27K is shorted to +9V. Or it should.

It is possible that your limiting resistor is shorted across it and cannot limit the current. That would account for the sudden death. Use your ohmmeter to measure back from the empty pin 5 socket pin to the limiting resistor (should be about 0.000 ohms) then to the *far* side of the 27K, where you should read the value of the 27K resistor. If you read less than the resistor value, then you have found your problem.

[Demone]

I'm going quite well... :lol:
I tried the 27k res and it gives me 26.9 so its ok.

Could it be that BEFORE the last .05 cap near the output I read 2.78v and AFTER 0v, a current factor ?

I dont know if I'm authorized to make all this stupid questions here they are too basic I think, if I'm annoying someone please tell me.

Thank you very very much for your help keen
:wink:

[Demone]

Ok, for those who may have the same kind of problem try to check your pots.
The 50k for the output was actually shorting thus giving no out going signal, thats it.