Help with my Rosscomp clone

[zeppman]

Hey guys.  I have just built a ross compressor clone form tonepad.com and small bear components.  I'm going to follow Arons procedure.

1.  Ross Comp clone

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

3. I followed tonepads schematic exactly, including their pcb board.  I only changed the 500k lin. pot to a 500k reverse audio taper, and the IC was a IC CA3080E as opposed to IC CA3080.

4. No part substitutions.  The only changes I made: I flipped the trim pot 180 degrees so now that "Y" shape of the three prongs is flipped.  I figured it didn't matter because that middle prong is still touching the same lead.  I also think I wired my pots backwards because I turn them counter clockwise to increase sustain and volume, I figured this didn't matter though.  

5. No special situations ( I think)  Aside from what I have noted I followed every step the same.

6. The pedal seems to do what it supposed to (sustain and a squished sound), yet I"m not sure how extreme the squish is supposed to get because this is my first compressor I have ever used.  The issue is that there is a terrible amount of noise.  It sounds like white noise on a TV, or rain.  Every once in a while there is a louder quick swish/pop.  This happens all the time, regardless if I'm playing or not.  There is no noise when in true-bypass mode.    

7.  IC, Transistor and Diode readings.  I will label the readings according to the schematic on the tonepad page as posted in the above link.  Both pots will be set exactly at 12:00  Battery = 9.44v

IC: CA3080E
1  0v
2  4.89v
3  4.88v
4  0v
5  0v
6  9.41v
7  2.61v
8  .64v

Q1
c 7.88
b 2.03
e 1.5

Q2
c 7.4
b 2.61
e 2.03

Q3
c 9.25
b 0
e 0

Q4
c 9.3v
b 0
e 0

Q5
c 9.41
b 9.33
e 8.8

d1
line side 9.4
no line  0

d2
line side 0
no line 0

d3
line side 0
no line 0

All help will be much appreciated.  Thanks guys.

[zeppman]

I think I numbered my IC pins backwards on the 5-8 side.  I numbered like this:

1  5
2  6
3  7
4  8

The dot is closest to pin 1.  Thanks

Sorry

[R.G.]

Just offhand, I'd say that the circuit is doing what it should, so the detailed voltages may not be much help. What you describe is likely to be a noisy OTA, or possibly a bad solder joint giving you noise.

Did you socket the 3080? If you did, replace it. If not, remelt every solder joint with just a touch of rosin core solder to eliminate bad joints. Let us know what happens.

[zeppman]

Thanks RG.  Should I completely remove the old solder before I apply more?  Or just heat it up to re-melt, and add a little.  It wouldn't be a bad transistor or the fact that I have the pots wired backwards, would it?

[zeppman]

Sorry RG, I didn't answer all your questions.  Yes, I did socket the IC.  What is an OTA?  (I'm kinda new to all this)

[Joep]

The CA3080 is the OTA

[zeppman]

Ok, to get another IC I would have to order one which would take a couple of days and $5 shipping (unless someone knows of a place in the chicago area where I can pick one up.  Should I just do that or resolder the whole board?  Most of my solders look good.  There are a few joints where I put a little much, and couple that don't have that shine to it like the others.  Could this be causing it?  Could it be a noisy capacitor instead?  I do have a multimeter and all the caps and resistors seemed to check out, but even if they have the right value can they still cause that "tv static" noise?  I'm a beginner at this stuff.  Is there any other way to go about testing this?  Someone please help!  Thanks guys.

[zeppman]

Ok, so I tried resoldering some stuff...now it doesn't work at all..BUT..  I put in an old 741 that I had laying around just for fun...and it works....kind of.  You really have to strum hard, and the sound comes through.  Otherwise it just knocks down the volume and sounds like normal.  Obviously it looks like the chip, right?

[R.G.]

I put in an old 741 that I had laying around just for fun...and it works....kind of. You really have to strum hard, and the sound comes through. Otherwise it just knocks down the volume and sounds like normal. Obviously it looks like the chip, right?

Not necessarily. The only thing that a 741 shares with a CA3080 is the fact that they both have eight pins. Not the same inside at all.

I think you need to find another CA3080 or LM3080. Sorry.

[zeppman]

Yeah, I'm ordering a new CA3080 from small bear...hopefully it will get here soon.  Has anyone else tried to build this?  What type of resistors and other compenents di you use?  .... 1% metal or 5% carbon?  Anyone with any info would be appreciated.  Is there anyway to be able just to "look" and see if it is a bad solder?

[jimbob]

I just about finished my second Ross clone. This one i decided to perf. Took a little longer than the board I bought but looks just as good. I ll list any changes differences ect..one i wire it up tomorrow. If you want a bigger challenge try to perf it. what a PITA. BTW Im using a nte996 for my OTA.

[bwanasonic]

What would be useful to know is the settings you are using on the compressor and on your amp. Are you using a clean amp setting? If you are using a clean amp setting and have both controls on the compressor at about halfway or lower, hiss should not be too horrible. If you have both controls cranked, yes you will get hiss and maybe nothing is wrong with your unit.

Kerry M

[zeppman]

I was getting hiss both on the clean and distortion channels...obviously it was less on the clean, but it was still there.  I understand there might be a little noise, but this is unbearable.  I would never be able to use it to gig.  Actually the pedal has stopped working for me now.  I plan on getting some probes for my pc so i can use it as an oscilliscope.  What type of resistors and transistors did you guys use?

[jimbob]

I just finished mine tonight and after realizing that i forgot to make a connection from the 56k resistor to the main line through the middle of the effect i gotr going. Very silent to my suprise. I did use a 1k trimmer but it didnt seem to make much of a difference. Its very smooth and warm compared to the dynacomp- which is more twangy.

[zeppman]

jimbob-

Did you use 1% resistors or 5%?

[jimbob]

I used all carbon film as i have NEVER noticed a difference. I also used 2n3904's, 47k resistors instead of 56k, 100ka instead of the 50ka for volume, 1k trimmer instead of 2k, an perfed it all. BTW- make sure you get something to scrape between your connections where theres not supposed to be anything. Thats what the problem may be. I use a dremmel to go through it  and make sure theres no solder bridges anywhere.

[bwanasonic]

BTW- make sure you get something to scrape between your connections where theres not supposed to be anything.

I love those pointy solder tool things with the other end perfect for bending leads.

Kerry M