Ross Compressor build not working HELP.

[DanielB]

Hi
I've just built a Ross Compressor via the fuzz central website. When testing if i dont play anything for a couple minutes then strum i get a very quickly decaying strum from it but after that nothing at all. Im very new to building so pretty rubbish at debugging.
here are some pin values
ic 1        2       3        4         5        6       7        8
   0      4.97   4.53     0       .64      2.6     9.6      0

     q1              q2                q3                q4             q5
c    8.97           9.68             8.57             8.57           9.68
b    1.25           2.6               0.49             0.26          8.58
e    .72             2.2               0                  0              9.55

any help would be tops
thanks
Daniel

[lopsided]

hey,
not sure about that, but i'd check the collector resistor at q2 (short, wrong value). The voltage should be lower then  supply voltage, I guess.

l_s

[DanielB]

Ok awesome, thanks man will check it out!

[DanielB]

There doesn't seem to be anything wrong there.... Arg its doing my head in!!!c Any other ideas... Anyone?

[sgoman]

So, this damn pedal is still there on my desk for a month, and I've never left a foot in half. Resistance tester and check back 2 times with bands of color, even before they were ok. Contacts, I do not think so. Capacitors oriented correctly, the same as the IC. This happens with the probe, the volume to about half of the source to the pins 2 and 3 to 6 instead of the audio, then silence, white noise, light, with volumes ball and tweakability of any kind on TRIMPOT potentiometers and ... nothing different, higher maximum noise biamco. voltages go to:

CI: 1: n.c.
      2:0,4
      3:0,4
      4: GND
      5:0,1
      6:7,6
      7: v.Batt
      8: n.n

      Q1 Q2  Q3 Q4 Q5
C   4    6.8 8.2 8.2 V.batt
B   3.8  7.6  0    0  8.2
E   3.8  6.8  0    0  8.2


PLEASE HELP ME!!!!

[sgoman]

Any suggestion? Please 

[PRR]

> Any suggestion? Please 

Give link to project, don't make others hunt-to-help.

Say what "V.batt" IS. You have other points at 8.2V; if V.batt is 8.2V that's one thing, if V.batt is 9.7V that's a different thing.

Review thread at top of forum DEBUGGING - What to do when it doesn't work. You gave many voltages, good; but the other info is also often necessary or helpful. R.G. didn't write that just to hear his keys clack.

I would add:

*) when there is a "Vref", "V/2", maybe "Vb" as in this case: give that point's voltage. Many chip-amps hang on this reference.

*) When the project HAS check-voltages, point out where yours seem to differ. It might get diagnostic juices flowing, even though some wrong voltages are red-herrings.

silence, white noise, light, with volumes ball and tweakability of any kind on TRIMPOT potentiometers and ... nothing different, higher maximum noise biamco. And type slower. Light? Ball? Biamco?

There is a 150K resistor near Q2. What is the voltage at each end?

[JDoyle]

Completely agree with PRR.

Your voltages show that something is wrong, but the way you showed them, and what you didn't tell us, leaves it next to impossible to diagnose what is wrong.

This ain't what you want to hear, but that doesn't make it any less true.

On the plus side though, chances are, once we get all the right info, we'll be able to figure it out and get it running with you.

Regards,

Jay Doyle

[sgoman]

First of all: I'm sorry, this post will be more specific. The last was translate automatically, I was running to the office so:

1. Ross compressor kit by musikding
2. http://www.musikding.de/product_info.php/language/en/info/p2644_Der-Compressor-Ross---Compressor-Bausatz.html
3. Anything done by musikding instruction
4. no changes
5. "Negative ground" (right?)
6. What it does: white noise from out, with the probe:  sound goes to pins 2 and 3 at half volume, at pin 6 instead of the audio in out white noise.

Nothing change with trimpot and/or pot variation.

CI: 1: n.c.
      2:0,4
      3:0,4
      4:GND
      5:0,1
      6:7,6
      7: 8,7 (battery voltage)
      8: n.c.

      Q1 Q2  Q3 Q4 Q5
C   4    6.8 8.2 8.2  8,7 (battery voltage)
B   3.8  7.6  0    0  8.2
E   3.8  6.8  0    0  8.2

[PRR]

There is a 150K resistor near Q2. What is the voltage at each end?

[sgoman]

150k resistor on the left side of IC connected to Q2 as asked: same Voltage of pin 6 by the internal side, 7,6v and 2v by the external side. Thanks in advance

[PRR]

> 7,6v and 2v

The 2V should be 3V, set (in the musikding plan) by R21 R22.

However this is the second "3080" I've seen recently which has 0.1V at pin 5 and 7V at pin 6, both wrong (should be 0.6V and 3V). I am suspecting bad 3080 chips. Where did you get yours, from Das Musikding or from eBay?

[sgoman]

The chip was in the musikding kit, so I wrote this morning to musikding that there was a problem with the kit, they replied me that a new IC is on the go! So...I will update you mounting the new IC when arrived. Thanks a lot now.

[sgoman]

Good news, the CA3080 wasn't working as it would, changing it with the new received the effect works! Thanx a lot to all 

[sgoman]

Bad news the effect doesn't  work as  previewed. I have a volume loss around 50% referred by the clean sound. I give you the incorrect voltages:

IC:

pin 2: 0,4
pin 3: 0,4
pin 5: 0,5

    Q1   Q2
C   4      4
B   3,8  0,2
E   3,8   3,5

Could you help me? Bye

[PRR]

There is a 150K resistor near Q2. What is the voltage at each end?

[sgoman]

Now...the resistor 150k near Q2 with new IC: 1,8v external side, 0,5v (the same of pin 5 obviously) by the internal side. Thanx

[PRR]

This is a real puzzle. All I can offer is clues.

R21 R22 provide "Vb", a reference voltage of about 2.8V. You should check this.

The 2.8V goes two places.



It goes through R11 R12 to Q1 Base. These are high-value resistors. We expect to find about 1.5V-2.0V at Q1 Base. Instead you report 3.8V! I can not see any way for this voltage to be high except a collector-base short at Q1. However you report a 0.2V difference collector to base.

It also goes through R13 to OTA Out and Q2 base. R13 is lower values and we do not expect much drop. Maybe 2.8V to 2.5V. However you report 1.8V at the high end, 0.2V at the low end.

There is also the low voltages at OTA input pins 2 and 3. R8 R9, R7, and R5 R6 should set these to about half the supply voltage, 4V or 5V. Instead you have a very low voltage. Check those resistors and trimmer. (You can replace the trimmer with two 1K resistors.)

[sgoman]

Vb out of R21/R22 is not 2,8v but 1,8v, with or without IC. Resitor double checked, band and ohm as expected. What can I do, replace all the resistor you cited?

[PRR]

> Vb out of R21/R22 is not 2,8v but 1,8v

Well, check my math.

Resistors 56k and 27K.  Total is 83K. We take Vb across the 27K. 27K is 0.325 of 83K.

Battery is 8.7V. 0.325 of 8.7V is 2.83V.

To get 1.8V with one of R21 R22 the right value you could have 56K+15K or 100K+27K. It is interesting that these "wrong" values are common values.