NJM4558D

[morgandorfer5150]

So while I'm not an expert, I have about 12 working builds under my belt so I've learned a lot so far. I seem to be having an issue with the NJM4558D sub for the JRC4558s that I'm trying to use in the Dream Fuzz and Noise Clamp. I've checked, rechecked and trike checked all resistor values and cap values (and polarity where applicable) in both pedals. Both pedals don't work and only pass small clipped bits of sound. Is thier some compatibility issue with the NJM4558Ds that Tayda is selling? I'm at a loss of what else can be wrong, it's got to be these ICs

 

[phi1]

I’ve used the NJMs from tayda without issues.

have you checked the voltage levels on the pins of the ICs? Do you have any other dual op amps you can try, like ne5532 or tl072? I imagine they’d work well in these circuits as well so it’d be a good test to see if the op amps are the problem.

 

[morgandorfer5150]

I have some 072s I can try. It's really strange, I don't know why tayda has them listed 3 times with 3 different skus. The data sheets are all the same ??‍

 

[falzhobel]

I have used 100s of them without trouble but maybe a bad batch ?

 

[morgandorfer5150]

That's what I'm wondering because I used one in the past for a tube screamer and it worked just fine. I'm going to try the tl072 later and see if I can rule out the IC

 

[morgandorfer5150]

Weird, as long as the chip is not fully flush against the board it works....bad pcb/eyelet? I'm at a loss. My last two builds are back-in-stock items. I wonder if theirs a quality control issue happening here.

 

[phi1]

Would be surprising if both your board happened to have an issue, and both happened to be on the op amp pads.

also, I’m not sure what you mean by flat against the board, or why that would make a difference. Did you use sockets, or are you de-soldering for each test? Multiple times de-soldering could weaken the pads.

 

[morgandorfer5150]

Yeah it definitely could be, i desoldered once to remove the suspect chip and then placed a TL072 and it's spot without soldering it seeing is it fit pretty snuggly it conducted just fine. With a Tl072 in place the board worked but it wasn't much of a op amp fuzz affect more of a dirty drive. I tried the same thing with a fresh 4558 I had on hand and it worked beautifuly! The weird thing was they only worked when the chip was still seated about a millimeter off the board standing up on its legs a bit. Seeing as it was working with the chips slightly lifted I soldered it in place with the chip slightly lifted and I was right back to where I was in the beginning. I chased each run from the chip to its corresponding components on the schematic and everything ohmed out perfectly. I also again just for pure fun checked every single component on the board for value and it's all correct. Double checked my switch wiring for about the millionth time and double-checked to make sure I had the jacks connected correctly (you just never know). Back to square one. I'm at a loss, tossed it in the bin, we'll chalk that one up failure same as the noise gate. The three boards I received at the same time were the Cobalt drive ( assembled and working perfectly) the muffler noise gate (fail), and the dream fuzz. The last two we're items that just recently came back in stock doesn't seem likely that there's a production failure but I guess it could happen. I'm not a stranger to builds, I've got quite a few functioning builds under my belt and those are my first two full on failures. I even recently built the spatialist list reverb (highly recommended by the way). ??‍ Maybe I need to take a break from petal building for a while, which is a shame because I just received my king of tone board today.

 

[phi1]

Yeah that is a weird scenario. I’m a big fan of socketing any op amps. Means you can always rule that out as a cause of failure pretty easily (among other advantages). If you get some, get the ones with machined round metal holes, they’re a more stable connection.

 

[morgandorfer5150]

I'm going to start doing that now. Thanks for the tip!

 

[morgandorfer5150]

Solved!!! After quite a bit of troubleshooting I have solved the issue and the muffler noise gate works beautifully! IMPORTANT! Q3 is backward in the board and on the build diagram! Install it 180 degrees from it's shown state. All other components values and polarity are good. If your muffler build is not clamping and is instead just making some low farting noises when wide open, reverse the direction of the 2n5485 FET! Works fantastically now! Great gate!