IS it possible to burn 3 opamps in 2 minutes?

[tambek]

yup. it's broken again. on my Shaka 5, a few times i had to switch the TL072 cause it was burnt, one time i had to resolder the power in lead, and it worked perfectly fine. Now it's quiet again. No sound at all when i switch the pedal on. Bypass is OK, also i checked - the problem is not in the switch, i tested, connected those 2 switch leads together (bypassed the FX), worked fine. I checked - I can hear the signal until it enters the IC. No problem - i get a new one. BUT, i still won't work. :shock:  I can hear the signal before the IC, but not after the IC, i changed the IC (TL072) a couple of times, so I think it can't be that those 2 new ones that I tried are also burnt already. (or just broken). Also - the IC is getting enough power (8,3V) to be exact. EVerything that needs power is getting it. So what could be the problem here... I would say it HAS TO BE the IC, but i tried 2 other ones too, or it HAS TO BE that the circuit is not getting power but it is...  :roll:

uh and... yep - the circuit is completely dead AFTER the IC, actually, the signal won't reach the Q1 and Q3...

http://www.muzique.com/schem/shaka5.gif


I'm outta me wisdom

[tambek]

I really thinkk it can't be the op-amp cause if they would have been burnt, they would have been hot and smelly. vbut they werwn't.... and - the power leads are connected correctly. not upside down or the worng way...

[aron]

Measure the pins on the op amp with respect to ground (red lead on pin, black on ground) and tell us.

Aron

[tambek]

okay... TL072.... here are my voltages....

      +--()--+
out1 | 1    8| Vcc+
in-1  | 2    7| out2
in+1 | 3    6| in-2
Vcc- | 4    5| in+2
      +------+

Pin 1 and 2  - 8,3V
Pin 3 and 4 0 (connected to ground)
Pin 8 - 9,3V
Pin 7 - Constantly changing between 4,5 to 8V (weird?)
Pin 6 - 1,7V
Pin 5 - 3,2V

[Paul Perry (Frostwave)]

I really thinkk it can't be the op-amp cause if they would have been burnt, they would have been hot and smelly. ...

...this isn't always the case, if you reverse the power, or overload the output, that will heat up the chip, but it is also possible to fry the input without any smoke.

one way to track down difficult wiring/short mishaps, is to measure voltages at all the socket points BEFORE the chip is plugged in.
Also, checking resistance to ground from each socket pin (before inserting chip, and before powering up) can provide clues, sometimes.

look on the bright side.. you're going to learn something!

[Mike Burgundy]

pins 5 and 6 don't look right at all, nether does the output.  Is this thing oscillating? Hmm. Take it out of it's socket and measure again please.

[The Tone God]

If it makes you feel better I put a couple hundred volts into a opamp just the other day. That let out quite a bit of the smoke. :roll:

Andrew

[niftydog]

this may be a stupid question.. but why does that schem specifiy a dual op amp when only one half is being used?  Anywho...

Constantly changing between 4,5 to 8V (weird?)

is this with or without a signal going in? If there's no signal present, there's something fishy going on. Disconnect R5 1k, use a known good op amp and audio probe it again.

[tambek]

hmmmm. don't remember right now. im at works so i can't check it out...

ill see when i get home