Help debugging DIY phaser (piedrita) : CA3080 dead ?

[alesk]

Hello,
i tried to debug this pedal i built more than a year ago,
with no success.
after i built it the first time, it produced no sound.
but at this time, i had a solder iron with a too thick pointer, and i think it's not impossible that i made a few
short cuts on the pcb.
so i got a new board, and started all again with a thinner solder iron.
of course, before soldering it again, i checked all the components values(resistors, capacitors, the pinout of the NPN and PNP transistors)
The only thing i couldn't check were the 5 IC (CA3080).
I read on another thread here that the CA3080 could die instantly if it's pin5 received more than 1ma; with my first attempt
with this effect, i think this may have happenned !

So, if someone could confirm the CA3080 are dead (or better, that i missed something obvious !), it would be nice...


1.What does it do, not do, and sound like?
2.Name of the circuit
3.Source of the circuit (URL of schematic or project)
4.Any modifications to the circuit? Y or N
5.Any parts substitutions? If yes, list them.
6.Positive ground to negative ground conversion? Y or N

1- output is either the same as input, or just mute (i think it depends if i turn the rate/depth pots)
2- piedrita (like EH small stone phaser)
3- http://www.tonepad.com/project.asp?id=11
4- Yes : just replaced R42 (4k7) a 2k resistor in series with a 5k lin pot (adding a depth pot)  
5- No

Measurements:

Voltage on the power supply = 9.10V
Voltage at the circuit board + = 9.10V
Voltage at the circuit board - = 0V

i also made some tests with an audio probe, out of the CA3080 or the transitors, but all i could hear (if i could hear something) was a very weak, saturated sound)

IC 1 to 5 are CA3080

IC1 :
pin1 : 0
pin2 : 0.74
pin3 : 0.74
pin4 : 0
pin5 : 0.74
pin6 : 1.82
pin7 : 5.39
pin8 : 0

IC2 :
pin1 : 0
pin2 : 0.74
pin3 : 0.74
pin4 : 0
pin5 : 0.74
pin6 : 1.79
pin7 : 5.39
pin8 : 0

IC3 :
pin1 : 0
pin2 : 0.63
pin3 : 0.74
pin4 : 0
pin5 : 0.74
pin6 : 0.49
pin7 : 5.39
pin8 : 0

IC4 :
pin1 : 0
pin2 : 0.85
pin3 : 0.74
pin4 : 0
pin5 : 0.74
pin6 : 5.39 (!)
pin7 : 5.39
pin8 : 0

IC5 :
pin1 : 0
pin2 : 1.17
pin3 : 1.17
pin4 : 0
pin5 : 0.67
pin6 : 2.61
pin7 : 5.39
pin8 : 0


Q1 : (NPN)
e : 0.29
b : 0.71
c : 5.37

Q2 : (PNP)
e : 5.39
b : 5.36
c : 0.7

Q3 : (NPN)
e : 1.29
b : 1.79
c : 5.36

Q4 : (NPN)
e : 0.73
b : 1.29
c : 5.38

Q5 : (NPN)
e : 1.27
b : 1.76
c : 5.36

Q6 : (NPN)
e : 0.72
b : 1.27
c : 5.38

Q7 : (NPN)
e : 0.29
b : 0.46
c : 5.38

Q8 : (NPN)
e : 0.29
b : 0.29
c : 5.38

Q9 : (NPN)
e : 4.87
b : 5.38
c : 5.35

Q10: (NPN)
e : 4.25
b : 4.87
c : 5.38

Q11: (PNP)
e : 1.77
b : 1.14
c : 1.76

Q12: (PNP)
e : 1.77
b : 1.14
c : 1.73

Q13: (NPN)
e : 1.87
b : 2.58
c : 1.88

Q14: (NPN)
e : 1.13
b : 1.87
c : 1.14

[Mark Hammer]

Though it won't sound qute as robust with 3 instead of 4 stages, you might consider jumpering and bypassing a stage at a time to see if it is just that one 3080, or something more generalized.

[alesk]

hi, and thanks for the reply!

you might consider jumpering and bypassing a stage at a time to see if it is just that one 3080, or something more generalized.

it seems to be a clever idea, i'll just have to find out how to do that...  
i suppose the 4 stages are from ic1 to ic4, and if i want to bypass stage2 i cut the connections marked in red :



i'll do that tomorrow, it's the evening in france...

[Mark Hammer]

I can't see the drawing here, but you would want to isolate the input of each stage from the output of the previous one.  That cut can be easily bridged again once you have identified the stage that has the problem.

C'est l'après-midi içi.

[alesk]

Hello again,

i tried to bypass the stages , no changes (no phasing effect)
i finally removed the 5 CA3080, and the sound is exactly the same as it is with them all !  
i guess they are all dead ?

C'est l'après-midi içi.

nice ! you speak french ? (but you would write "ici" , the "ç" is for sounding like an "s" in cases it would sound like "k", for example :"ça ne marche pas !")

[Mark Hammer]

J'ai toujours des confusions avec la cédille.  Comme fonctionnaire je dois parler et écrire les deux langues officiels, mais je ne suis pas parfaitment bilingue  Tout de même, j'essaie.

The Piedrita has MANY transistors.  Are you certain they are all oriented properly?

[alesk]

J'ai toujours des confusions avec la cédille.  Comme fonctionnaire je dois parler et écrire les deux langues officiels, mais je ne suis pas parfaitment bilingue  Tout de même, j'essaie.

you speak very well ! you're doing more than trying !

yes 14 transistors is a lot..
i remember testing them all for checking the pins (ebc) with my multimeter before putting them back on the pcb.
(just in case the pinout would be different from one brand to another, but i don't even know if it's possible)
anyway, i had no surprises, and then i put them just like on the drawing from the pdf file.

i don't know if you still can't see the pictures, but i posted one of my board, orientation is the same as on the pdf.
and after reading the build reports on tonepad, there seems to have no mistakes on the pdf...

[Mark Hammer]

I made one, using BC550 and BC560.  It worked fine, however the BC550 has the opposite pinout to the 2N5088.

Je comprend que c'est mathématiquement impossible, mais avec 3 jambes il y a au moins 823 moyens de faire un erreur!  

[alesk]

 
well, you sure are right, but what troubles me is that i only used 2N5088 and 2N5087 as written on the pdf...
so the orientation should be the same as on the drawing, right? (and i checked their pinout before putting them on board)
anyway,  i'll check again... (but i'm pretty sure, it's ok)
maybe the best thing to do is to buy some other CA3080 to be sure...

thank you very much for your time anyway !

[Mark Hammer]

The CA3080 is becoming rare AND expensive, while the availability and cost of the 2N5952 are becoming more favourable.  It may be wiser to attempt a clone of the Ross phaser (which is a Small Stone using the cheaper and more available LM13600 and op-amp input and mixing stages), or to buy a small pile of 2N5952 and make a Phase 90.  You can buy a small handful of 2N5952 for the same cost as a CA3080, and an LM13600 (= 2x3080) can also be purchased for very little.

[alesk]

you are right again, i already considered giving up with this fx, and starting a new phaser like the phase 90.
the thing is i already built like 10 guitar/bass fx, and a 12ax7 guitar preamp that all work perfect,
and it's kind of frustrating staying on a failure !
but you are right, i'd better stop with this one and try another model...
thanks!

[Mark Hammer]

Well, don't stop trying to de-bug this build.  You already have the money invested in the CA3080s, and the problem may not be those chips but something simple elsewhere in the circuit.  I just don't think it is wise to throw money at buying more 3080s unless you really need them (e.g., to repair a well-loved synth).

However, sometimes it is is faster and easier to just build something new than to figure out why something already built isn't working.  I wish it wasn't that way, but sometimes it is.

[Thomeeque]

 If you are really tired by this one, build DynaComp (or RossComp*) meanwhile, it's an easy build, nice compressor and you can use it as CA3080 tester T.

* I may even offer my own verified layout

[alesk]

Well, don't stop trying to de-bug this build.  You already have the money invested in the CA3080s, and the problem may not be those chips but something simple elsewhere in the circuit.  I just don't think it is wise to throw money at buying more 3080s unless you really need them (e.g., to repair a well-loved synth).

However, sometimes it is is faster and easier to just build something new than to figure out why something already built isn't working.  I wish it wasn't that way, but sometimes it is.

yes, you're right.
i'll stop spending money on that one for now unless i find out what's wrong with it.

If you are really tired by this one, build DynaComp (or RossComp*) meanwhile, it's an easy build, nice compressor and you can use it as CA3080 tester

* I may even offer my own verified layout

i love the idea of building that comp as a CA3080 tester !  
i checked your link, and   , this thing is crazy, and superb !
i downloaded your pdf, i think there's everything i need to build that comp (modded by the same "Mark" who's posting here ?)
thanks for sharing !

[alesk]

Btw, i just rechecked all transistors for their pinout by measuring their hfe with my multimeter (is it the right way to do it ?)
everything seems ok...

[Mark Hammer]

Okay, that's one less thing to wonder about.

One of the things I like to do is find points in the circuit where I can measure AC voltages to assure myself they are in an appropriate range.  You can do that without having to cut any traces.

The first place to begin is to measure the output of the input stage (the 5088/5087 pair), on the negative side of that 10uf cap.

By the way, do you get bypassed sound?  Do you know that the switch works?

[alesk]

ok, i just measured the negative side of C3 (10uf) : 2.83v

i didn't put any bypass switch yet (i usually check if the fx works ok before i do that).

[Mark Hammer]

Is that with a guitar signal or without any input at all?

[alesk]

it's without any input.

[alesk]

just checked with an input, it's the same....