Need help on Rat 2! It's not working after opamp mod!

[mattdavios]

hi guys,

I am new to the forum however i had tried a few mods on DS-1 and SD-1 with the past threads on the forum and they work great. I am working on a rat 2 with a LM308 chip, decided to change its 9v jack to boss style 9V jack and the LM308 to a NE5532P opamp made by texas instrument. I also used a op amp socket in case i burn the chip. However after installation there wasn't any sound but the LED was lighted up when on. I tried changing position of the chip and it didnt help. Anyone knows what went wrong? My adaptor was down so i couldnt test the 9V jack...could it be the 9V jack that was not installed correctly or something is wrong with the chip that causes the pedal to not work? Really appreciate your help and thank you in advance.    

[PenPen]

Uhm, did you reroute the pins? Those chips aren't pin compatible. From the datasheet the NE5532P is a dual OA, all of the pins are different from the LM308.

[mattdavios]

i didnt reroute the pins...how do i do that Thanks a lot for your help 

[PenPen]

Are you modifying a stock pedal or is this a DIY build? If it is a stock pedal you should just go back to the LM308 or use an LM071 with the compensation cap removed, you can't really do any rerouting with the PCB.

Otherwise, the LM308 pins are as follows:

1- Compensation
2- IN -
3- IN +
4- V- (GND)
5- NC (No connect)
6- OUT
7- V+
8- Compensation

The NE5532P is:
1- OUT1
2- IN1-
3- IN1+
4- V-
5- IN2+
6- IN2-
7- OUT2
8- V+

Basically, if you were going to reroute things, you'd have to use only one half of the NE5532P, and map pins as follows, LM308 to NE5532P:
6 - 1
2 - 2
3 - 3
4 - 4
7 - 8

And remove the cap connecting pins 1 and 8. Not an easy job. You'd really have to design it to use that OA.

[petemoore]

  Rat uses 308, a 'compensated' oa, for a 'regular oa Rat'..., IIRC someone was doing some 'standard OA' Ratwork...maybe something made it into layout galleries?

[oldrocker]

Yes the pins would be different for a 5532 dual and a 308.  I used 741 and it sounded pretty good which ignored the compensation caps.

[mattdavios]

wow! i didnt know about all this..thanks for the information Penpen.I bought the following op amps
RC4558P
LM833N
OPA2134PA

will you be able to tell me which op amp i will be able to use in place of LM308?

[Minion]

You can"t use any of those 3 Opamps in place of the LM308...You need a Single Opamp not a Dual opamp and all of the Opamps you have bought are Dual opamps...A good replacement might be a OPA134 (You bought a OPA2134 which is a Dual opamp) and the LM833 which you bought is a 1.5w dual Power Amp IC which isn"t suitable either and the RC4558 is also a Dual opamp.....

Look for a OPA134 or a TL071 or a NE5534 , These are all Single opamps and there are Literally Hunderds of different types that could also work but also thousands of others that won"t work....

You should spend some time reading the Datasheet specs of these Opamps so you know what to look for when you need to replace them.....


Cheers

[mattdavios]

gee...should had asked and read up more before buying them. I wont have problem using those Dual OP amp on my boss sd-1 am i right? Thanks a lot for your help

[petemoore]

  Not sure, someone probably is.
  I had a DS-1 with an inline 8pin dual opamp.
  I can't recommend how I wrangled in the standard dual opamp where the inline came out!
 

[darron]

i changed the opamp in a rat to a NE5534AN without any mods. it went straight in.