Tonepad Ross compressor debug

[Plinky]

I decided to build a Ross compressor clone using the layout from the Tonepad site (http://www.tonepad.com/getFileInfo.asp?id=9) using all the add-on parts for the Ross compressor and I was using the voltage charts off of the Fuzz Central site for reference (http://fuzzcentral.ssguitar.com/ross.php).

I etched my own circuit board (no open traces detected). Used 2n5088s in stead of 2n3904s. There were a few components I couldn't get the exact value, but I chose the next highest value, so I don't think that it would make that much difference (221pf instead of 220pf, .068uf instead of .05uf). I am using a 500K rev log pot for the sustain control.

What it's doing - bypass operation ok, no sound when engaged. I originally had tantalum caps in place for all the electrolytics, but after it wouldn't work I switched them back to electrolytics. I have swapped the IC out with no luck. Measured all my resistors prior to installation and triple checked the pcb for unwanted solder traces and have found none.

voltages: taken with the sustain control all the way down and the 2k trimpot set to the middle position per the Fuzz Central site (no switched mods added)

power at 9v pad on pcb - 9.6v

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

Q1
C - 7.56v
B - 2.4v
E - 2.0v

Q2
C - 7.1v
B - 2.9v
E - 2.4v

Q3
C - 9.6v
B - 100mv
E - 0v

Q4
C - 9.6v
B - 45mv
E - 0v

Q5
C - 9.6v
B - 9.6v
E - 9.6v

Diodes

D1
A - 0v
K - 9.6v

D2
A - 0v
K - 47mv

D3
A - -0v
K - 29mv


From what I can tell, my problem lies at pins 2 & 3 of the IC, which leads me to think the problem is at Q1, but the voltages there aren't far from the Fuzz Central readings (except for the readings at Q5).
Any little kick in the right direction would be greatly appreciated.

[oskar]

What it's doing - bypass operation ok, no sound when engaged. I originally had tantalum caps in place for all the electrolytics, but after it wouldn't work I switched them back to electrolytics. I have swapped the IC out with no luck. Measured all my resistors prior to installation and triple checked the pcb for unwanted solder traces and have found none.

voltages: taken with the sustain control all the way down and the 2k trimpot set to the middle position per the Fuzz Central site (no switched mods added)

power at 9v pad on pcb - 9.6v

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

From what I can tell, my problem lies at pins 2 & 3 of the IC, which leads me to think the problem is at Q1, but the voltages there aren't far from the Fuzz Central readings (except for the readings at Q5).
Any little kick in the right direction would be greatly appreciated.

First of all I would like to salute you to an all exemplary posting of your technical problem with Oh! so many voltage readings...   
1. The voltage on IC pin 2,3 should be higher yes so right now C... (why do people leave out component numbers? BAD idea!... ) the capacitor to the right of
Q1 is turned the wrong way. Because of the erronious voltages. Pull out Q1 of the sockets temporarily and pull out the IC too.
2. Now meassure the resistance from the IC pin 2 to ground and V+ and post your readings...
3. An OTA bias input is referenced to ONE diod voltage drop... pin 5 should be ~6V. Sounds like the IC could be oriented the wrong way...

oskar

[Plinky]

I can only assume you mean the 1uf electro just after the emitter on Q1. Both it and the IC are oriented exactly like the photos on Tonepad

http://www.tonepad.com/photoessay.asp?photoEssayID=32&sequenceNo=3

Is there a problem with the layout that I haven't found?? From looking at the schematic and the layout they're both correct.

If I turn up the sustain control all the way, the voltage on pin 5 of the IC will read about 6.8v. This reading was taken with the sustain all the way off (counter-clockwise), just like the instructions on the Fuzz Central site. According to that page, it should be around .6v, but I am using a 500k rev. log pot for the sustain control rather than the 500k linear that is asked for, so that may the difference there.

[oskar]

If I turn up the sustain control all the way, the voltage on pin 5 of the IC will read about 6.8v. This reading was taken with the sustain all the way off (counter-clockwise), just like the instructions on the Fuzz Central site. According to that page, it should be around .6v, but I am using a 500k rev. log pot for the sustain control rather than the 500k linear that is asked for, so that may the difference there.

No! It should be around 0.6V anyway.

[oskar]

I can only assume you mean the 1uf electro just after the emitter on Q1. Both it and the IC are oriented exactly like the photos on Tonepad

Yes after the emi... erh!... arrow thing.          Again, what is the resistance to ground from the inputs of the IC?
Sooner or later I'm going to ask you for a pic of the pcb. Sooner... pic please? Booth sides.

Is there a problem with the layout that I haven't found?? From looking at the schematic and the layout they're both correct.

Hardly. The amounts of buildreports at Tonepads indicates no problems at all.

If I turn up the sustain control all the way, the voltage on pin 5 of the IC will read about 6.8v. This reading was taken with the sustain all the way off (counter-clockwise), just like the instructions on the Fuzz Central site. According to that page, it should be around .6v, but I am using a 500k rev. log pot for the sustain control rather than the 500k linear that is asked for, so that may the difference there.

The internal diode on input 5 on the 3080 chip goes to pin4/ V-. There isn't a proper connection from pin4 V- to ground, otherwise it
would definitely be around 0.6V

EDIT! Added 3080 schemo from the datasheet... Most IC schematics leave out lots of details but I think this is the actual one because
the 3080 is that simple...
Note D1/Q3 this is why we know the voltage should be 0.6V at pin5.





oskar

[Plinky]

Give me sec...The transistors aren't socketed. I'll post my findings ASAP.

[Plinky]

Pull out Q1 of the sockets temporarily and pull out the IC too.
Now meassure the resistance from the IC pin 2 to ground and V+ and post your readings...

Do you mean the V+ & V- pins on the IC socket or the power & ground pads on the pcb???

[oskar]

Pull out Q1 of the sockets temporarily and pull out the IC too.
Now meassure the resistance from the IC pin 2 to ground and V+ and post your readings...

Do you mean the V+ & V- pins on the IC socket or the power & ground pads on the pcb???

I meant on the PCB but they should really be the same...
I only meant pull out the transistor if it IS in a socket... don't desolder anything for this!

[Plinky]

Too late! Not a big deal. I can solder it back in real quick, and I have plenty of replacements.

resistance readings:

pin 2 of IC socket to 9v pad - 254 K ohms
pin 2 of IC socket to grnd pad - 257 K ohms

I wasn't sure at first, so I also measured from pin 2 of the IC socket to pin 4 (V-) and from pin 2 to pin 7 (V+). I ended up with identical readings. (257K & 254K)

[oskar]

Too late!

oops!       

resistance readings:
pin 2 of IC socket to 9v pad - 254 K ohms
pin 2 of IC socket to grnd pad - 257 K ohms
I wasn't sure at first, so I also measured from pin 2 of the IC socket to pin 4 (V-) and from pin 2 to pin 7 (V+). I ended up with identical readings. (257K & 254K)

Should be 400-500k on both readings... sort of... I think... etc.
Which brings me to suspect cap marked Cc turned wrong way or just bad or shorted... or a combination of these!

[oskar]

What does Vb read and what is the voltage on Cc?

[Plinky]

What does Vb read and what is the voltage on Cc?

Not sure what Vb was or where to measure it (yet ).

I did previously measure both sides of the 1uf electro. If I remember correctly, it was about 2-2.1v on the neg. side of the cap (about the same as at the emitter of Q1) and about .5-.6v on the pos. side (close to what I was getting at pin 2 of the IC).

[oskar]

No. the voltage between Rd, Re...

EDIT (I've been drinking way too much coffee, again...)
1. Voltage between cap Cc,Rd,Re
2. Vb = bias voltage... check upper left part of drawing.

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

[Plinky]

EDIT (I've been drinking way too much coffee, again...)

Ditto. You ought to try soldering on a caffeine rush.

No. the voltage between Rd, Re...

9.6v going into Re, 5.04v out, 5.04v into Rd, .6v out (like a good little noob I replaced Rd, which did no good )

1. Voltage between cap Cc,Rd,Re
2. Vb = bias voltage... check upper left part of drawing.

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

Had 4.8v at the pos. leg of Cc
measured voltage at Rb - had 3.1v at the top, 2.7v at the bottom

[oskar]

EDIT (I've been drinking way too much coffee, again...)

Ditto. You ought to try soldering on a caffeine rush.

I did it for a living... I worked with pcb's in a heatcamerafactory last summer... all on caffeine. They even sent the stuff into orbit.
  everytime they check the shields on the spaceshuttle for dammages... It's with machines I've actually been into... and if they mention
it on the news... it means I'm sleepless... (caffeine or not!)     

9.6v going into Re, 5.04v out, 5.04v into Rd, .6v out (like a good little noob I replaced Rd, which did no good )

Voltage in the crossing Rd,Re,Cc should be arund 7Volts (leave the soldering iron for a while...      )
Something is sinking the durrent dropping the voltage to 0.6V (which happens to be a diode forward voltage drop... but not necessarily (don't touch that iron))
Could you please tell me the colour code on the 1M resistors? ( and don't change them... yet!)

Had 4.8v at the pos. leg of Cc
measured voltage at Rb - had 3.1v at the top, 2.7v at the bottom

Now wait a minute!
the positive leg of Cc is 4.8V and Rd, Re is 5.04...    they are connected and should read the same!
Vb is 3.1V which sounds good.
0.6V out of Rd, that is at the trimpot? WHIT THE IC NOT IN THE SOCKET?   
And replacing Rd? You're definitely on the case... but at least leave the resistors, you measured them before you put them in
and they are not that sensitive. Look for shorts and unsoldered parts instead...
I'm off for a late dinner and some TV... it's 20.50 in Stockholm
I need to catch some sleep... I'm back tomorrow...   

[Plinky]

Thanks for the help. It's about 2pm here in Dallas, Texas. I have some errands to run, but when I get a chance, I'll definitely look this over and post my findings.

[Plinky]

Voltage in the crossing Rd,Re,Cc should be around 7Volts (leave the soldering iron for a while...      )
Something is sinking the current dropping the voltage to 0.6V (which happens to be a diode forward voltage drop... but not necessarily (don't touch that iron))
Could you please tell me the colour code on the 1M resistors? ( and don't change them... yet!)

That's what I was thinking (sounded like a good thing to say ). The colors of the 1M resistors are brown, black, black, yellow

Had 4.8v at the pos. leg of Cc

Now wait a minute!
the positive leg of Cc is 4.8V and Rd, Re is 5.04...    they are connected and should read the same!

Oops! I just had a poor connection with my test lead. I double checked and it's 5.04v at the pos. leg of Cc.

0.6V out of Rd, that is at the trimpot? WITH THE IC NOT IN THE SOCKET?   

That is with the IC installed. I removed it and took readings again:

1 - 0v
2 - 5.0v (huh?!?!?)
3 - 5.0v (wtf?!?!?!)
4 - 0v
5 - 8.8v
6 - 2.9v
7 - 9.6v
8 - 0v

And replacing Rd? You're definitely on the case... but at least leave the resistors, you measured them before you put them in
and they are not that sensitive. Look for shorts and unsoldered parts instead...

Doing that at this moment (yet again).

[oskar]

Readings with the IC removed

1 - 0v                                 <---- not connected
2 - 5.0v (huh?!?!?)               <---- the error (the 3080! is gone...)
3 - 5.0v (wtf?!?!?!)               <---- the error (this means the resistor/capacitor net in front of the OTA is working as it should)
4 - 0v                            <------ ground
5 - 8.8v                     <---- bias good
6 - 2.9v                            <---- looks good
7 - 9.6v                  <---- connected!!!
8 - 0v                                 <---- not connected                           
... All well!!!

The case looks like this...
1. IC turned the wrong way
The IC could have written signs on it but the notch/indent indicates the pins one and eight.
2. IC is wrong IC not a 3080
It has the text 3080E (or some other letter) on the back?
3. IC is bad.
Well if it aint case one or two I'll drop a mail to Intersil and ask if there has been problems with this chip...
Could you please report on the exact text on the back of the chip...
It isn't very likely for the IC to be wrong... less likely for two of them failing... actually the whole batch that theese chips came
from could be wrong, I've actually experienced it, but it isn't very likely at all.

It looks to me like the 3080 is turned the wrong way/ or is not a 3080 after all or whatever... I've seen some pretty freaky errors but
in this case I don't suspect intersil(who made the chip) to have done wrong.

[Plinky]

The case looks like this...
1. IC turned the wrong way
The IC could have written signs on it but the notch/indent indicates the pins one and eight.
2. IC is wrong IC not a 3080
It has the text 3080E (or some other letter) on the back?
3. IC is bad.
Well if it aint case one or two I'll drop a mail to Intersil and ask if there has been problems with this chip...
Could you please report on the exact text on the back of the chip...
It isn't very likely for the IC to be wrong... less likely for two of them failing... actually the whole batch that theese chips came
from could be wrong, I've actually experienced it, but it isn't very likely at all.

It looks to me like the 3080 is turned the wrong way/ or is not a 3080 after all or whatever... I've seen some pretty freaky errors but
in this case I don't suspect intersil(who made the chip) to have done wrong.

The CA3080E is not from Intersil. It's from Harris Semiconductor. I bought 5 of them online from Effects Connection.

http://www.effectsconnection.com/oscommerce/product_info.php?cPath=36&products_id=266&osCsid=a29e1c803ac9c6f232b2c05a3eedf9bc

On the back is some raised lettering (L5 in a circle). The pic on the store website is identical to what I have.  I have the notch on the IC and socket pointed towards the 2K trimpot, just like all the pics I've seen.

[oskar]

The CA3080E is not from Intersil. It's from Harris Semiconductor. I bought 5 of them online from Effects Connection.

http://www.effectsconnection.com/oscommerce/product_info.php?cPath=36&products_id=266&osCsid=a29e1c803ac9c6f232b2c05a3eedf9bc

On the back is some raised lettering (L5 in a cirle). The pic on the store website is identical to what I have. 

Intersil bought harris ------ voilá!   
You bought FIVE?! Just pop a fresh one in there then!... what are you waiting for?