SOLVED Rodent problem

Idroj

Idroj

Active member
Hi! And this is the 3rd and for now, last faulty pedal I build. A RAT that, now that I remember, I got from Tayda, pcb included. I built it, and similar to the Blue Breaker, I was able to enjoy it for a few seconds and then nothing.. I took it out of the enclosure, used this system that this youtube explained to narrow down if the problem is in the pcb board or the wiring, and it only worked for a moment, sounded amazing, but just for those few seconds. Now that I fixed 2 pedals this week with your all your help, and learning lots of things, I guess that a good place to start would be a good cleaning, right? I'll also have to try to unplug some pads and re-wire the 3PDT switch board...

Should I reflow anything else or just start the IPA toothbrush cleaning and put it all back together?

If I get to fix this one, after having fixed the other 2, this will be a HUGE VICTORY! Thanks everyone for taking the time to help out!

IMG_7749.jpg IMG_7750.jpg IMG_7751.jpg IMG_7752.jpg Diagram to test PCBs b4 wiring.jpg
 
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You should cleanup the old solder on the 3pdt board. Do you have a solder wick or solder sucker? You can IPA board now.

I know the YouTube channel you're talking about. That guy is a great resource for anyone. Did you say you tested it with alligator clips like in the video or via the whole kit?
 
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I cleaned everything up with IPA, redid all the wiring and VOILA! Victory! It works!! This has been amazing.. I had 3 faulty pedals in my drawer, I almost gave this up, and thanks to this forum I was able to repair all 3 of them! What an euphoric few days.. you should've heard the screams: YES! YES! Thanks, thanks, thanks!! ?? And I have a new soldering iron coming tomorrow... I'm unstoppable now! ??
 
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Good Deal!!! If you like the sound of this one, track down a LM308N (not from e-bay though, most likely fakes) and build a Muroidea. Use Ge diodes for the clipping diodes and its a sweet sounding distortion pedal, same as a You Dirty Rat. Some people say the op amp makes a difference and others say it doesn't. What I found out is both camp are right and both camps are wrong. Some circuits sound the same no matter the op amp, while others sound better with certain ones. A Rat has more grit and nastiness with a LM308 verses an OP07. And that is meant in a good way.
 
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Awesome I will do that! Could I just swap my current OP07 with a LM308N or do I need a new circuit for that? Also, if it's not ebay, where could I find authentic LM308s? I am after grit and nastiness! Thanks.
 
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Idroj said:
Awesome I will do that! Could I just swap my current OP07 with a LM308N or do I need a new circuit for that? Also, if it's not ebay, where could I find authentic LM308s? I am after grit and nastiness! Thanks.
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The difference is more subtle than you think. You could find one on Mouser or Jameco. Smallbear has them but they're out of stock right now.

Yes, it's easy to swap out provided you put some sockets in. For experimenting, sockets are essential and you can find them almost anywhere (amazon, ebay, tayda, etc.). It saves you the time and effort for desoldering and resoldering.
 
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Yes you can. I looked at board and thought it was a TL072, its actually a TL071! An OP07 or a LM308N will go right in. With the OP07 or TL071 C3 30pF cap is not needed. With a LM308N it is. Since you included it any IC will work. Even an OP07 might sound better than a TL071.
I've found the LM308N at a few different places, they come and go as they get them. So you have to find them when you can. You can also use a LM301N which is in stock here https://www.futurlec.com/Linear/LM301ANpr.shtml. The big difference is the slew rate of the op amps. The 308/301 are set by the 30pF cap at .5V/uS the TL series has a slew rate of 13V/uS.
 
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BuddytheReow said:
The difference is more subtle than you think.
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I used to think the same way, I was building a rat for my daughter a while back, and had all the parts and did all my research. After populating the board I was finishing the enclosure and had a 308 chip fall into my lap, literally. Someone had it laying around in a drawer from years ago, it was for a repair of an obsolete circuit board that they no longer had. He gave it to me for free. I used this on the pedal and Man did it sound good. Since I had a spare OP07 I decided I wanted one also. Built a second one with the OP07. Did a side by side of the two and the OP07 was not the same as the 308N. Searched high and low for the LM308N and found some, put one in the circuit and BAM! The two pedals were real close. Hers still has a bit of an edge, I believe she got the older chip!?:ROFLMAO: I'm not a huge believer in the "MOJO" parts camp, but I have found that certain components work better in certain circuits. In this case the LM308N does sound better. And no matter what, I would change out the TL071 in this circuit, not a huge fan of the TL chips, if you push them to hard they break up.
 
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Ok I will look for a LM308N, also and OP07 and swap them and hear it for myself! Even if subtle, I will probably be able to notice it. I mix every single day on good monitors and it is all about subtleties. I once had a Proco RAT in the studio during an album, it was a new one from few years ago.. I ended putting a little of it in parallel on vocals a lot... worked great for that!
 
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I could be mistaken, but I do think the OP07 uses a compensation capacitor (and this is one of the reasons it was chosen as the replacement of LM308s).

The Tayda PCB may not include that cap, since it was designed for the TL071, so you may need to wire the cap yourself to the pins of the IC if you swap either the LM308N or OP07 in.

There's many who think TL071s sound better in RATs anyway, but better is all a matter of preference.
 
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spi said:
I could be mistaken, but I do think the OP07 uses a compensation capacitor (and this is one of the reasons it was chosen as the replacement of LM308s).

The Tayda PCB may not include that cap, since it was designed for the TL071, so you may need to wire the cap yourself to the pins of the IC if you swap either the LM308N or OP07 in.

There's many who think TL071s sound better in RATs anyway, but better is all a matter of preference.
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Not at all! It is internally compensated. With OP07 the 30 pF cap is not needed. With the 308N you can change the slew rate with the cap size.

I checked the Tadya docs and the 30pF cap is there
 
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