Which 14-pin opamp should I use?

[jakenold]

Hi guys 

I need you help on this matter. I'm building a distortionbox, and the one I've based my design from has a 14-pin IC without any identification codes on it.

My question is: How can I identify this chip? Or is there no other way than to purchase some 14-pin chips and try them in my circuit? I can do some readings from the chip with my multimeter, if that's of any help.

Thanks in advance! 

[Seljer]

Measuring the voltages on each of the pins would be one step.

Tracing the schematic would be another part, as you could decipher what each pin is by knowing what its connected to.

Other than that, if your IC has no markings on the top, there is often a small code on the bottom as well which you might be able to use to figure out what it is.

[jakenold]

Thanks for your input Sejler.

Should I measure the voltage on each pin with my multimeter, while having one probe connected to ground at all times? I can see that pin 7 is connected to ground and I have already traced out the schematic. I will get back to you when I've desoldered the chip.

[jakenold]

Alright, I've been measuring the voltages across the pins, and I came up with this:

Pin 1: 7.49V        Pin14: 7.49V
Pin 2: 3.50V        Pin13: 5.09V
Pin 3: 3.35V        Pin12: 4.80V
Pin 4: 3.60V        Pin11: 3.37V
Pin 5: 3.15V        Pin10: 3.42V
Pin 6: 3.37V        Pin 9: 3.34V
Pin 7: Ground/NC    Pin 8: 3.68V

There were no writing what so ever on the bottom, and the top has been sanded so anything on there is gone too. I can send you the schematic if that would help you. Although I won't post it here, as it is somebody elses work and I'd have to ask for his permission first. There is 9V across the curcuit.

[Dirk_Hendrik]

How about stop to torturing yourself? Are you even sure you're dealing with an Opamp?

How about throwing the thing away and start off with a component of which you do know wat it is? There's literally thousands of 14 pin IC's around. Therefore it could very well be that you're dealing with something like a memory chip and will never get anything out of it.

In the case that you would live around the corner (slim chance) I'd be glad to give you an identifyable 14 pin IC to start off and get you in the right direction  a possible succes.

And in the case you are positive that the IC is an opamp... best of luch is to wire it line a TL074 or a LM324. Connection diagrams can be found on www.datasheetarchive.com

[jakenold]

Thanks for your response Dirk.

I know, this project has been a torture to begin with, but I'm obsessed with fixing and modifying this pedal. The manufactor covered it in black epoxy which I had to remove and then desolder the defect IC. I took these measurements from my buddies pedal, so for me it's still worth the 200$ these things cost here in Denmark.

[MartyMart]

The name of the "original" might help us to help you !
.... It wouldn't be either a "TC" or a "T-rex" would it ... 
( it may also be a cmos chip, 4069UBE !! )

MM

[slacker]

It's probably not an opamp, most 14 pin opamps have +volts as pin 4 and ground as pin 11.

[Dirk_Hendrik]

The name of the "original" might help us to help you !
.... It wouldn't be either a "TC" or a "T-rex" would it ... 
( it may also be a cmos chip, 4069UBE !! )

MM

Indeed. This is new and very different info. Suddenly we're talking about fixing something existing instead of bulding a fuzz wit an unknown component. What are you fixing? Gut photo's do help as well. And, ++ important, What made you decide the component was defective.

[jakenold]

Dear Mart

No, it's the 3rd danish producer - EMMA. It's the ReezaFRATzitz. I am very sad but I cannot post the schematic in here. They are a small company, and I truely respect their work. It's just that my pedal's not covered by warrenty anymore, and I can't spend 1000$ on gear a month any more, as I'm studying. 

I've been studying the pedal, and all it has are two diodes, one transistor and then this IC. My spare knowledge tells me it must be some kind of opamp. Please do correct me if I'm mistaken.

[jakenold]

Indeed. This is new and very different info. Suddenly we're talking about fixing something existing instead of bulding a fuzz wit an unknown component. What are you fixing? Gut photo's do help as well. And, ++ important, What made you decide the component was defective.

The IC was brown in the middle, and had burned a hole through aprox. 1 cm of black epoxy. I've tested the other components, and they respond the same way my buddy's pedal does.

[Dirk_Hendrik]

That's fast!  Still,
What are you fixing?

[markm]

Sometimes additional damage can occur with the removal of epoxy.  
You may be fighting an uphill battle here.

[Dirk_Hendrik]

Sometimes additional damage can occur with the removal of epoxy.  
You may be fighting an uphill battle here.

Experience?
I still have bad dreams from an OCD I had to fix last week

[jakenold]

Dirk: Did you manage to put down a schem of that thing?  That would be awesome

Mark: I've heated it with hairdryer and carefully removed it from the PCB. It came if pretty easy, but in small bits. All in all it took me around 4 hours to remove it all, remove the chip and install a 14 pin socket.

[markm]

Mark: I've heated it with hairdryer and carefully removed it from the PCB. It came if pretty easy, but in small bits. All in all it took me around 4 hours to remove it all, remove the chip and install a 14 pin socket.

Now that's determination 

[Dirk_Hendrik]

....

Kinda reluctant to share since the subject is pretty heavy, especcially on this board.

Essentially think a Dist+ with BS170's instead of Clipping diodes. First moint Gate to Drain, 2nd mount Gate to source.

[jakenold]

Dirk: I fully understand. Although I have a split-oppinion on that. Makers of great pedals should be able to make money from their works, but DIY'ers will still try to replicate it, no matter if you as a manufactor supply the schematic or not. There's a reason very few, new patents for effect pedals exist - especially for drive-pedals, and that reason starts with 808... 

Anyway, I think there is a difference to be made between Mike Fuller and EMMA. Now, back to the matter at hand... 

[puretube]

try a 4069 for fun...  

(but then: of course there has been a (outside?) reason,
that chip fried out...)

BTW: dunno what that pedal is...



[EDIT:] Hah - funny: write a reply, hit the submit button, go to the kitchen to look after the food, come back, and see the red letters:
...other posts in the meantime...
hit the submit button again,
and find the answer is already there...

[Paul Perry (Frostwave)]

The only way it is possible to actually burn a chip (to the extent that damage is visible) is by connecting one of its pins to the mains. It simply can't happen otherwise (a mere battery or plugpack hasn't enough power, in my experience).
So, there could be one or two other things damaged...... but I have seen a few things that have been struck in this way, and the chips usually act as fuses OK!!