Need help building Ibanez Tube screamer.

[Izzy]

http://www.smallbearelec.com/Detail.bok?no=86

is this the one?

[Izzy]

and looks like just now I fried my IC JRC4885. I dont know how. theer is this  hmmmmmmmmmm sound in opamps output 1 and at 5 other legs are working. I dont know what's wrong.haha

This stupid adapter has been giving me 14v even at 9v!

[MikeH]

Yeah that's the stuff.  Although your voltage issue might be part of the problem too.

[Izzy]

Thanks Once again Sir. So do you think My IC is fried?

[MikeH]

I don't know.  If you do a search for the datasheet it will tell you how much voltage it can handle. 

[Izzy]

Ican handle 18 V.
It was working fine till yesterday. Today mourning when I tried to use it. Then  it doesnot work Properly.

[Izzy]

Does anyone know what could be the problem? Is it the opamp?

[Izzy]

can anyone rescue me?

[petemoore]

  Sounds like something changed, perhaps the voltage on the pins changed also. I would re-take the voltage measurements.
  If the chips shows good bias it's probably good, if you've socketted it you can swap to use process of elimination opamp test [the only way I know to test an OA is to set it up in a circuit that biases it...a known working circuit, and see how it compares to a known working OA...sound and bias wise].

[Izzy]

Thanks Petemore, I appreciate your hjelp.
Can you please explain lil more in detail? I am kinda new to those  those stuff.
Thanks iN advance

[GibsonGM]

Hi Izzy,

The standard 'debugging method' here (In the FAQ) is to measure all your pin voltages and post them.  The 4558 can handle +/-18v, IIRC, but that is measured from a correctly biased source.   What he means is to check voltages, and if nothing jumps out at you, take the chip and put it in another circuit that you KNOW works with a 4558.  That could be something simple from the data sheet that you know works with a new IC.   That's about the only way to test an IC for failure.  No easy ways around it. 

Seems like you already have a suspect, your adapter!   I make my circuits to work on battery only at first, no stomp switch, and if I want an adapter/switches  I'll add one after I know it works...there's an engineering maxim called "KISS"...Keep It Simple Stupid!     Learn about Zener diodes if you are worried about that 14v...a 9.1V zener could help you regulate that.  Post voltages...

Good luck,

Mike

[Izzy]

Hey my rescue man is here!! hurray!   

Ok I did as you said. But before that my prime suspect. I guess its the adapter because when I measure the voltage its gives me 17.xx- 18.xx volt at any place where I set 3v-12 v in my universal adapter. It was giving me 14.xx V yesterday. So I guess that 18 V either destroyed my Opamp or my capacitor!
How do we find out whether the caps are working or not?

Beside that here are what I emasured with  9.08 V battery


1.What does it do, not do, and sound like:
It was working fine  the day when I made it. even though there was small amount of noise/hum. ( I assume my adapter was running at 14 v at that day.) By the end of the day it burnt my 2 LEDs.
The next day I guess adapter suddenly changed to 18.xx volt for no reason. Now it sounds like  quaaaaaaaaaaaaaaaaaa and changes pitch if I touch it. It even makes noise when I turn off now. It was workign fine when I turned off till yesterday.

2.Name of the circuit = Ibanez TS-9/808
3.Source of the circuit (URL of schematic or project) = Tonepad
4.Any modifications to the circuit? Y


6.Positive ground to negative ground conversion? Neg ground (I guess thats what is it)

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 9.08V

Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead = 9.09
Voltage at the circuit board end of the black battery lead = 0



Q1 (2N3904)
C =9
B =4.5
E =4.13

Q2  (2N3904)
C=9
B=4.27
E=3.7

IC1 (JRC4885)
P1 = 8.45
P2 = 7.6
P3 = 6.64
p4 = 0
p5 = 9.17
p6 = 8.5
p7 = 8.5
p8 = 8.25

[Izzy]

I just tried to play it wthout the IC then it sounds fine when it is bypassed.

And when I plug in the opamp, even when it is by passed it gives. quiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii sound. When I touch the input jack of guitar the pitch goes higher.

So I am suspecting its the opamp.
But Please help me here with your experience!
Thanks in Advance.

[GibsonGM]

I'd say the OA is porked, Izzy    It happens; I keep spares for this!  The quiiiiii is self-oscillation.

Read this:  http://www.repairfaq.org/sam/captest.htm#cttes

I'd try bridging the electrolytics 1 at a time to see if it makes the oscillation go away before doing anything else.  It's probably the IC that got popped by the voltage, tho.  An audio probe after the signal in (with signal applied, lol) will tell you if the caps in the signal path are dead.  No audio = dead.  This might actually be the easiest way to go.

What you might try doing after that is, with just the battery - no adapter, measure the voltages at the socket pins with NO IC in place.   You should get battery V on pin 8, 0 on pin 4.  About 0 on the other pins, I think (no schematic right here).  If this is the case, go ahead & put a new 4558 in.

That should get you going!
Good luck!

[Izzy]

I'd try bridging the electrolytics 1 at a time to see if it makes the oscillation go away before doing anything else.  It's probably the IC that got popped by the voltage, tho.  An audio probe after the signal in (with signal applied, lol) will tell you if the caps in the signal path are dead.  No audio = dead.  This might actually be the easiest way to go.

Did you mean shorting the caps?

[Izzy]

Ok Gibson GM , I did as you said.

I checked the voltage at the IC sockets with the IC removed.

Then

P1 - 4.5 V
P2 - 4.3 V
P3 - 4.5 V
P4 - 0 V
P5 - 9 V
P6 - 4.5 V
P7 - 4.5 V
P8 - 4.5 V

Schematic:
http://img365.imageshack.us/img365/6855/creamerwg0.jpg



Then I tried to check with audio probe, the quiiiiiiiiiiiiiiiiiiiiiiiiiiiii sound comes from everywhere in the circuit.

Then I removed IC and checked  the signal from the input. The signal goes fine till opamp. after that there is no connection (Since opamp removed)

So probably opamp?

[Jay Doyle]

Sounds like it Izzy. I'd toss that adapter out, by the way. 

Use a battery, replace the opamp with any dual you have lying around and see if that works. With the voltages you have without an opamp in there, it looks good.

I think a new opamp will do the trick...

[MikeH]

This is also why you might have had trouble getting more gain out of the tubescreamer.  At higher voltages, it would have greater headroom and distort less.  Anyone want to back me up on that?  I'm no expert on Tubescreamers at higher voltages, but that sounds right to me.

[Jay Doyle]

This is also why you might have had trouble getting more gain out of the tubescreamer.  At higher voltages, it would have greater headroom and distort less.  Anyone want to back me up on that?  I'm no expert on Tubescreamers at higher voltages, but that sounds right to me.

Sorry, but I can't back you up on that. 

With the diodes in the feedback loop, the voltage swing is limited to 1.2V peak to peak so whether at 9V or 18V the distortion/gain will be dependant on the size of the drive pot. For overdriving regular amplifier stages you are correct, but diode clippers change the game.

BUT, the tone control section will sound more 'open', to my ears at least. And you will have less of a chance of distorting the highs in that part of the opamp. I know that in EQs that use gyrators and caps to form EQ bands, a higher voltage tends to sound more 'open' as well.

[Izzy]

Thanks you. I again Aprreciate your help.

Yes I will surely toss that adapter out. IF i had any dual opamp around I would try it but right now I dont have any . I will have to wait till my order gets here from small bear.

Since you said high voltage will affect the tone. Probably that explain why I was getting sudden change in tone at higher level.Till 80% of tone control it moved smoothy and after 80 % it suddenlt used to change to high trebly noisy sound. Probably  because of high voltage?