GGG Ross Comp Help

[williamsij]

All,

I need some help on this. Has anyone else done the Ross Compressor Clone from GGG? I have not had any luck.

Here's the full information that's suggested:

1. Ross Compressor Clone, from General Guitar Gadgets.

2.Links
http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=79&Itemid=26
http://www.generalguitargadgets.com/diagrams/geo_d&r_comp.pdf

3. I followed the instructions to a "T".  Even the ones that didn't make it into the pdf....
Please Note:There are errors in the PDF file.
C2 should be value of 220pF, the parts list lists it as 0.0022uF (2200pF).
C11 should be value 0.001uF instead of 0.01uF
C12 should be 0.01uF instead of 0.1uf
The values listed in the PDF file for C2 and C11 will cause a substantial loss in treble sounds. Trim pot is 2k value.

4.Any parts substitutions or modifications you made to the original: This is where it gets interesting.....
On top of the mods from above, I also found a FEW OTHER ERROS in the pdf. First, the transistor numbers on the board layout don't match up with the transistor numbers in the schematic.  So when I refer to a transistor, look at the board layout.  (On the schematic, Q5=Q2, Q2=Q4, Q4=Q5). Second, the wiring for the sustain on the board layout doesn't match the wiring on the schematic. I actually followed the Fuzz Central layout for that pot (http://fuzzcentral.ssguitar.com/ross.php).  It looked like it was basically the same thing.

5. It is a "Negative ground" circuit.

6. It passes a clean signal when off. The LED turns on, when on.  When I use the audio probe, I can follow the signal to the IC. On the IC there is a clean sound on pins 2, 3, and 5. There is a distorted sound on pins 1 and 8. And there's no sound on pins 4, 6, and 7. I know that no sound on pin 6 is a problem, but I don't know why its doing that. I've tried swapping out ICs and I get the same results. 

Here's my voltages:

Voltage in: 9.44V (from 1-spot)
Ground: 0V

IC (CA3080E)
1  0.15V
2  0.62V
3  0.67V
4  0V
5  1.47V
6  2.54V (bad ground noise came thru amp when I checked this voltage)
7  9.44V
8  0.15V

Q1
C  7.36V
B  1.45V
E  2.00V

Q2 (from board layout, Q5 on schematic)
C  7.01V
B  2.54V (bad ground noise came thru amp when I checked this voltage)
E  2.36V (got a radio station when I checked this voltage)

Q3
C  8.23V (voltage dropped to this when checking)
B  0V (got a radio station on my amp when I checked this voltage)
E  0V

Q4 (from board layout, Q2 on schematic)
C  8.23V (voltage dropped to this when checking)
B  0V
E  0V

Q5 (from board layout, Q4 on schematic)
C  9.44V
B 8.23V (voltage dropped to this when checking)
E 8.93V (got a radio station on my amp when I checked this voltage)

D1
C  9.44V
A  0V

D2
C  0V
A  0V

D3
C  0V
A  0V

Please help! I've been working on this for a couple weeks now, and I just want to get it finished. Any information that anyone can offer would be GREATLY appreciated.


Also, I'd just like to know if anyone has done the GGG Ross Clone before.  I feel like I'm the guinea pig or something. Shouldn't they have all the bugs worked out with the pdf before they post it??? Also, there was a short on my board that fried a transistor. There were two leads touching that shouldn't have been.

[Pushtone]

Yes, many here have built the Ross Comp from the GEO D&R pdf file (BTW its not a GGG project, it's just hosted there).

I've built two and they work fine.
Its been a while and I can't remember any difference between the layout and the schematic, but I'm sure I only looked at the layout while building.
I would go back and conform your board to the layout and forget about the schem or whatever fuzz central is doing.

I'm assuming you didn't do a search on the forum because you would have learned that A LOT of folks have built it.
Usually the first post a person throws up after building a Ross Comp is about the distortion.
Thats normal for this circuit, especially with humbuckers. Turn down your guitar volume to clean it up.

And to GGG defense, at least he added the error notes to his page. He did not create the pdf.

[williamsij]

I'm not trying to rip on GGG. Actually, he helped me out quite a bit to get to where I am (thanks JD!).  He doesn't have one built up, so he couldn't check the voltages. That's why I'm here.... trying to get more info. 

I'm not complaining about distortion tho.  I don't have any sound at Pin 6 of the IC.  That's where I'm stuck. Any help here?

[kawayanstrat]

I didn't tried the GGG version,but built the tonepad's version. I would consider tonepad's layout compare to GGG,cuz it's already been verified.
And tonepad has a build report page on every project .

[oskar]

Hi!
Check R14...

[williamsij]

What am I looking for on R14?    Can you please be more specific? Thanks

[Pushtone]

Perhaps he means for you to check it for cold solder joint and/or its value.
I can't copy and paste from the PDF (file won't allow it) but there is a description of what R14 C11 is doing.
If I understand the "how it works" part of the pdf, it would make sense that you get hum on pin 6 because there is Vbias voltage there.


I'm bothered that you have distorted sound on pins 1 & 8 because they are both NC (non-connect).
They are not connected to anything on the layout. In the CA3080 datasheet, the internal schematic also shows (by omitting) that they are not used in the IC.
I'm wondering if you have the IC in the wrong way, or if you are counting the pins in the wrong order.

I remember with my debug session I forgot the jumper between Q4 & Q5 (on the layout). Then it worked OK.

Have you checked the pin-out (C,B,E) of your transistors? Do they match the layout?

I would check my units voltages but I loaned it out. This thread made me realize buddy still had it.
Maybe I can get it back over the weekend. Have you found any other posted voltages?

Does adjusting the trimmer have any effect you can detect, sound or voltage wise?

Grasping at straws here but there must be a reason for all this.

My first Small Stone PCB build looked great but no sound. I finally had to etch another board and transfer parts.
The second one worked. I still don't know what I did wrong on the first one.
Perhaps you should consider a second board and a second try at it. Perhaps a different layout. RG can be cryptic at times to us newbs.

[williamsij]

I checked for cold solder and its value. All transistors and the IC are oriented properly. I've gone over the layout a million times, and everything matches up that I can see. I spent a little more time searching the site and found this (http://www.diystompboxes.com/smfforum/index.php?topic=63801.0).  I've tried multiple IC's, but my voltages seem to match his so I may have to try a few more. Does anyone know how to test an CA3080? I wouldn't think that I would be sent 2 that don't work, but I guess you never know.  Also, does anyone know if I can use the voltages off the Fuzz Central as references, or would someone be willing to post their own from a working GEO Ross clone?

Thanks for all the suggestions.

[Pushtone]

would someone be willing to post their own from a working GEO Ross clone?

Turns out that Buddy has had my comp in his desk draw here at work for two weeks.
Never even plugged it in. Last time I loan him a pedal to try out.

I will post the pin and Q voltages tonight when I get home.
I'm interested to see if I get any sound on pins 1 and/or 8 since they are NC.

Post anything specific you would like me to look for.
Otherwise I'll follow your voltage test point from the original message.

I'm thinking that pin 6 will vary in voltage depending on the position of the SUSTAIN pot.

[williamsij]

Yeah, I thought it was weird that I was getting small voltages and distorted sound at the unconnected pins. I just marked it up to some sort of internal connection in the IC?!?!?

Can you post voltages for sustain at 0 and 100%? And for Vb?

I don't know what Vb is supposed to be, but it looks like, if that is messed up, then my volates on IC pins 2, 3, and 5 will be messed up too.

Thanks for all your help Pushtone!

[oskar]

http://www.diystompboxes.com/smfforum/index.php?topic=59742.0

Hi! Sorry for the last reply...
This link is from an earlier 3080 error search where I show off a more verbose side     

Perhaps he means for you to check it for cold solder joint and/or its value.

That is what I meant... so-rry!
I don't have time to read up on the subject of OTA's but they are sort of noisy so c11 is a low-pass filter.  r14 converts the current
output from the OTA to a voltage... I think...


oskar

[williamsij]

..... I got my ICs from Effects Connection.... they're Harris 

Wish I woulda found these threads before deciding to do the Ross clone. I'd of ordered from Small Bear! They're soo good on everything else tho.

[Pushtone]

Here are my voltages:

GEO R-COMP
Layout from D&R Comp pdf hosted at GGG.


Voltage in: 9.41V (I also used a VS 1-spot adapter)

IC (CA3080E)
1  0V
2  4.01V
3  4.01V
4  0V
5  0.63V
6  2.58V Sustain @ min (3.04V Sustain @ max)
7  9.41V
8  0V

Q1
C  7.31V
B  1.46V
E  2.02V

Q2 (from board layout, Q5 on schematic)
C  6.94V
B  2.58V
E  2.40V (got a radio station when I checked this voltage)

Q3
C  8.19V
B  0V
E  0V

Q4 (from board layout, Q2 on schematic)
C  8.20V
B  0V
E  0V

Q5 (from board layout, Q4 on schematic)
C  9.41V
B 8.20V
E 8.80V

D1
C  9.41V
A  0V

D2
C  0V
A  0V

D3
C  0V
A  0V


Vb - metered at the junction of R13/R14/R15/C11
Trimmer at min - 2.83V
Trimmer at max - 3.16
Trimmer at 1/2 - 3.0 (this is where I leave it set for use)


So, after comparing yours to mine I'm suspicious of your trimmer. See pins 2 and 3 voltages.
Trimmers are easily damage by heat. When I meter the three trimmer pins I get 4.01V on each one.
Also check R6, R7, R8, R10 leading up to the trimmer.

All your other voltages are really close to mine except pin 5.

Hope this is helpful

Dave

[oskar]

Howdy... here are the meassured voltages for the IC pasted together.
The first one is from Plinky ( Chris P. ) in the link from my last post.
I don't know what really was going on in that case but whatever was haunting his circuit also bit yours.

Dave, as you said, it shouldn't be anything happening on pin 1 and 8...   


IC1
1 - 143mv
2 - .60v
3 - .61v
4 - 0v
5 - 1.4v
6 - 2.9v
7 - 9.6v
8 - 142mv

IC (CA3080E)

1  0.15V
2  0.62V
3  0.67V
4  0V
5  1.47V
6  2.54V (bad ground noise came thru amp when I checked this voltage)
7  9.44V
8  0.15V

Here are my voltages:

IC (CA3080E)

1  0V
2  4.01V
3  4.01V
4  0V
5  0.63V
6  2.58V Sustain @ min (3.04V Sustain @ max)
7  9.41V
8  0V

..... I got my ICs from Effects Connection.... they're Harris 

Wish I woulda found these threads before deciding to do the Ross clone. I'd of ordered from Small Bear! They're soo good on everything else tho.

Are you really sure it's a 3080?
I checked Effects Connection and I couldn't even find that chip in they're store???


skar

[williamsij]

I'm sure that they're 3080s.... I sent an email to Effects connection, and he replied saying that he took them off his site until he could look into it further.

[JDoyle]

check to see if pin 5 is a diode drop above ground, if not, you fried the chip.

Dave has a lot of good points - looking briefly at the layout on GGG, pins 1 and 8 aren't connected to anything and don't have any internal connection so something is very wrong there (I don't know for certain but if the leads for pins 1 and 8 are internally connected to the semiconductor substrate, which you may have proved they are, so this may not be a TOTAL waste, :-), a fried chip would make them the anode of the multiple diodes you made when you fried the chip, making the distortion you are getting understandable) . Plus if you fried that trimmer, there is NO WAY you would be able to get this circuit to work - the inputs need to be balanced and the area that they are is really, really small. A 60mV difference is enough to either saturate or cut off the chip.

So, replace the trimmer and use a heat sink while you solder it in. If that doesn't work, you may need to just wait for another 3080...

Regards,

Jay Doyle

[williamsij]

Hi all,

I got my CA3080s from Small Bear Elec today. I threw it in and it works!! Thanks to everyone for your help!