Help debugging DIY phaser (piedrita) : CA3080 dead ?

[Jazznoise]

The Emitter voltages for Q1 and Q2 look wrong - Q2's Emitter should be sitting around 9v as it's coupled to the power rail. Can you check your power supply is functional? What's causing the rail to be clamped around 5 to 6v - have you been using VBias where the power rails should have been? Q4,6,8 and 10 have the same issues on their emitter and 3,5,7 and 9 should probably be sitting a volt or 2 higher than they currently are.

When this has been resolved and other problems persist: check continuity between the input resistor and the input side of the capacitor, check the capacitor is in correctly, check between the otherside of the cap and the base of the transistor. Check between the emitter of the transistor to the base of the 2nd transistor, then both transistors emitters to the 4k7 resistor etc. etc. and see if there's a point in the signal path that's not connected.

After just testing those and a couple of O/P resistors we should see if you can get the clean half of the output. The phased half should then be checked by the same means - if the signal path is solid then it's back to step 1.

[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

* I may even offer my own verified layout

i love the idea of building that comp as a CA3080 tester !  

Great then!

i checked your link, and   , this thing is crazy, and superb !

Oh, thanks, I'm glad you like it! (so my self-promo did work! )

i downloaded your pdf, i think there's everything i need to build that comp

Should be, let me know (in that thread, not here) if not.

(modded by the same "Mark" who's posting here ?)

Yep, that would be him

thanks for sharing !

My pleasure, good luck! T.

[alesk]

The Emitter voltages for Q1 and Q2 look wrong - Q2's Emitter should be sitting around 9v as it's coupled to the power rail. Can you check your power supply is functional? What's causing the rail to be clamped around 5 to 6v - have you been using VBias where the power rails should have been? Q4,6,8 and 10 have the same issues on their emitter and 3,5,7 and 9 should probably be sitting a volt or 2 higher than they currently are.

thanks, the power supply is functionnal (although it's a DIY one), it powers my other pedals with no problem.

i measured again it's output : 9.06v

i have 9.06v on the board before R2 (470R) , and 6.54v after it, (i should be the same all along the power rail on the board, because of R2 that is between the power input and the power rail on the board, i think !) and so 6.54 again at Q2 emitter. (and 2.07v at Q1 emitter)
but i noticed voltages changed when it moved the depth pot i added (mod).
so i'm going to remove that mod, put R42 like it should be, and measure all the voltages again on transitors and ICs.
i'll post that when done...

have you been using VBias where the power rails should have been?

hum... i'm not sure i understand the question! my electronic skill are weaker than my english level (that is not really great!) 
if that's what going to pin3 of IC1 to 4, i had the same voltage everywhere!
but i'll measure that again and let you know.

Thomeeque : yes your self promo did work !
about "the" Mark, i just remembered i saw his name on a few projects i built !
i guess it's kind of he's fault i began DIY , and partially he's fault i'm stuck with this one ! (just kidding!)

[alesk]

ok, so i removed the "depth" mod, and restored the 4k7 R42.
(i wish i could modify my first post , but it seems like i can't...)
new measurements :

Voltage on the power supply = 9.07V

IC1 :
pin1 : 0
pin2 : 2.74
pin3 : 2.70
pin4 : 0
pin5 : 0.7
pin6 : 5.03
pin7 : 6.54
pin8 : 0

IC2 :
pin1 : 0
pin2 : 2.61
pin3 : 2.70
pin4 : 0
pin5 : 0.7
pin6 : 0.56
pin7 : 6.54
pin8 : 0

IC3 :
pin1 : 0
pin2 : 2.73
pin3 : 2.70
pin4 : 0
pin5 : 0.7
pin6 : 6.41
pin7 : 6.54
pin8 : 0

IC4 :
pin1 : 0
pin2 : 2.72
pin3 : 2.70
pin4 : 0
pin5 : 0.7
pin6 : 0.68
pin7 : 6.54
pin8 : 0

IC5 :
pin1 : 0
pin2 : 2.02
pin3 : 2.02
pin4 : 0
pin5 : 0.68
pin6 : 1.89
pin7 : 6.55
pin8 : 0


Q1 : (NPN)
e : 2.13
b : 2.57
c : 5.95

Q2 : (PNP)
e : 6.55
b : 5.94
c : 3.94

Q3 : (NPN)
e : 4.53
b : 5.04
c : 6.52

Q4 : (NPN)
e : 3.93
b : 4.53
c : 6.54

Q5 : (NPN)
e : 1.14
b : 0.56
c : 6.54

Q6 : (NPN)
e : 1.15
b : 1.14
c : 6.55

Q7 : (NPN)
e : 6.01
b : 6.41
c : 6.52

Q8 : (NPN)
e : 5.40
b : 6.01
c : 6.54

Q9 : (NPN)
e : 0.61
b : 0.68
c : 6.54

Q10: (NPN)
e : 0.61
b : 0.60
c : 6.54

Q11: (PNP)
e : 2.67
b : 2.03
c : 2.65

Q12: (PNP)
e : 2.67
b : 2.04
c : 2.65

Q13: (NPN)
e : 1.38
b : 1.89
c : 6.51

Q14: (NPN)
e : 0.77
b : 1.38
c : 2.04

[alesk]

check continuity between the input resistor and the input side of the capacitor, check the capacitor is in correctly, check between the otherside of the cap and the base of the transistor.

it's ok with that.

Check between the emitter of the transistor to the base of the 2nd transistor,  

you probably meant the collector of Q1 to the base of Q2 ? it's ok

then both transistors emitters to the 4k7 resistor

you probably meant the emitter of Q1 and  the collector of Q2 to R42 (4k7) ? it's ok

etc. etc. and see if there's a point in the signal path that's not connected.

mmm, i'll need a few days/weeks to do that !  

[Jazznoise]

That's o.k, my English is better than my electronics and mon francais est vraiment merde.  


I assume your depth pot was instead of the 27k and 30k resistors before the output? I find the voltage drop across the 470 odd. Is it a 470 and not a 4K7?

Please check if there's a signal coming from the 30k resistor after Q2 - just hook it up to a jack and play through it! If it works, then all of the transistor stages should work.

[alesk]

I assume your depth pot was instead of the 27k and 30k resistors before the output?

no, it was instead of R42 (4k7) connected to the emitter of Q1 and collector of Q2 (in orange on the picture above)

I find the voltage drop across the 470 odd. Is it a 470 and not a 4K7?

i just rechecked, and althought it's violet ring looks more like brown, it's a 470R , yes!

Please check if there's a signal coming from the 30k resistor after Q2 - just hook it up to a jack and play through it! If it works, then all of the transistor stages should work.

ok, just did it : between Q2 and the 30k (R8), the signal is much stronger than it is on input.
and after R8, it's weaker.

thanks for your time !
(btw, is your signature related to sonic youth? "♪ ♪ We're gonna kill the California girls...♪ ♪")


(btw n°2, i hope Mark isn't in a bad mood because of my horrible humor!)

[Mark Hammer]

Pas de problème.  Peau épais.   

[alesk]

ouf ! déjà que je suis nouveau ici, que j'ai un humour un peu bizarre et que la traduction n'aide pas, j'ai douté à un moment ! 
blague à part, internet est formidable, et c est grâce à des personnes comme toi que j'ai commencé à faire des effets !

[Mark Hammer]

Merçi de ta gentillesse. 

"Ouf" est un mot très peu rencontré ce coté de l'océan!  Peut être dans un livre d'Asterix ou Tintin, mais pas dans la conversation typique.

But back to a language more here can understand....

It looks like jazznoise is successfully guiding you through the trouble shooting.

[Jazznoise]

Haha, "the milk maid maidenhead!"! 

That makes sense. So we know your input transistor works. Now take the same wire from the jack and stick it after the 10uF cap before the first OTA. And then to the output of your OTA. Ca marche ou ca marche pas? C'est la questionne!

..I'll stop. And you don't get off that easy, Mark, you don't know how much I don't know about OTA's!   

[alesk]

Now take the same wire from the jack and stick it after the 10uF cap before the first OTA. And then to the output of your OTA. Ca marche ou ca marche pas? C'est la questionne!

so after the 10uF cap (C3), the sound is ok.
then after R25, it's a lot weaker.
then after IC1 (pin6), it's a bit stronger than on IC1 input (but seems to have more high freq, and it's still weaker than after C3)

strange thing (?), the sound is the same on emitter and collector side of Q3. (is this normal?)

Q4 : sound on emitter side only, weaker and more "dirty"...
if i quickly probe the outputs of IC2, IC3, IC4 the sound is weaker and weaker (to barely audible)

seems like  more i go on on signal path, weaker and more dirty is the sound...

[Jazznoise]

Yes, it's the same current being drawn through emitter and collector so the signal should be the same unless something naughty is happening.

Do you mean dirty as in, distorting or just noisey? I actually just simulated those little longtailed amps using a pair of 2N5088's and the gain of each stage is about 0.5 (Meaning or signal is 1/16th or -24dB of itself upon output) I had to change the 10k resistor going from ground to the 47k resistor  to 100K to get near unity gain (well, 0.9). But that's no good because after 4 stages we've gone from, say, 1 volt to 0.66 volts which is close to 6db.

So I say take out the 10k resistor in the first stage and see if that makes it better. If yes, do it on every stage!

[alesk]

by dirty, i meant distorting.

So I say take out the 10k resistor in the first stage and see if that makes it better. If yes, do it on every stage!

So i removed R31 (10k) , unfortunately no audible change...