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My rat is really squeaky ( is this oscillation?). This seems to worsen with increased treble. Also in the clipping section volume is very low when the switch has connected the center wire to the top wire on switch 1 and leds will not light up ( I guess they’re not being pushed hard enough). I disconnected the switch and tested by contacting wires directly to verify it is the upper connection of switch one that is quiet.
voltagec-9.36
b-.213
e-0
i know I’ve been a bit of a problem child lately but I feel I’m learning a lot. Thanks guys.
I had an lm308n in it and swapped it for this ua741cp I got in the rat mod kit that started me on this pedal building journey, while troubleshooting. I don’t think it made much difference.
Anyone? Is there more info I can supply?
The build doc specifically states that you must use an LM308 or OP07 opamp. The circuit has not been verified for use with other chips. If you still have issues when using an LM308, you should look elsewhere for a solution assuming the LM308 is a good chip.
The clipping performance varies greatly with the many possible switch positions of SW1 and SW2. The LEDs are not in the circuit in several of those combinations. Consult the RATT CLIPPING CHART in the build doc for more details.
Center position uses no less and works fine. There’s something not working quite right in the third pathway. I’ve swapped back and forth between the 308 and the other op amp with no difference relating to my issues. I’m learning more on my mm each day so I will check continuity tonight. I do get signal there it’s just very quiet. As for the chirping I tried touching the leads of a 104 cmm cap to the signal in and ground and that seems to help but I dont know what other effects that may have on the overall circuit as it’s hard to hold it in place flip a switch and strum a bass at the same time. I have incorporated the use of my foot for the strumming. Thanks for the reply.
Ollie, Ray just emailed me to see if I had an opinion on the IC you used. My best guess is that this is the issue, especially since you had the other one in the socket with the same result.
I would do the following:
- Start with verifying that all the capacitors are correct value. We can’t see this in your photo.
- Next, go to Resistors, make sure the stripes match what they should be.
- Then verify orientation of polarized parts. I can’t even see D2 in your photo, because it is either very out of focus or the transistor is in the way.
- I would say that for relatively new builders, 80% of issues (maybe higher) are caused by bad solder joints. More on this in a bit, but I would carefully bend up the PCB-mounted pots and re-flow all your solder joints. They should be Hershey kiss shaped, not blobs or balls, and shiny, not dull
A ton of people have build this circuit and this revision of the board. I know Barry’s manufacturer does an e-test of every individual PCB. They have a device which touches all pads and tests connectivity between each pad that is supposed to be connected per the CAD files. So unless you damaged the board somehow, it’s not the PCB.
I looked up your posts on this forum since I am not a very active moderator and you mentioned that you have been a problem child lately.
So here’s some advice–Up your game. Here’s what I mean:
- Make sure that you measure every part (that you can) before it goes onto the PCB.
- The Alpha pots we use are 20% tolerance. Make sure they are not more than that, and many pieces will be within 10% tolerance. If you have one that is close to 20% off or higher, ask on the forum if you should use it or replace it before you solder it to the PCB.
- Measure your resistors. It takes about 5 seconds per resistor, but saves a lot of time later. Try to solder all your resistors so they are read from the bottom or right side of the board, not just any-which-a-way. Makes it easier to determine value they are later.
- Get a multimeter that measures capacitance if your does not. There are affordable ones that do this, and while you’re at it, get an auto-ranging DMM for resistors, it makes measuring those easier.
- If your soldering iron doesn’t accept Hakko-style tips, get one that does. There are good soldering irons for $40 on Amazon which fit the bill. They can be generic. Get a set of tips that include a real pointy one and a narrow stubby one for soldering pots.
- Solder every component like you’re building something for the international space station. If the soldering looks mediocre, it is. Like I said, this is where most issues arise. Become a master solderhand. Also get good at de-soldering. Part of this is finding tools which work well. I use an Edysn “Soldapullt” brand solder sucker. I turned Barry onto this about 3-4 years ago after he had soldered for over 10 years, and he was blown away and couldn’t believe the difference compared to the past when he used a similar but inferior product. Last I looked, Amazon had an Edsyn model on clearance for cheap.
If you establish strong requirements for the way you build, you’ll have far fewer issues. And when you post on the forum here, we really want to see both sides of the PCB, not just the component side, and potentially the wiring too. And the pics need to be in focus (see image below, it’s not). Keep in mind that component side alone doesn’t tell us much when the part markings are not visible, like on the MLCC capacitors.
FWIW, from what I can tell from the MUFF’n image above the solder joints on the resistors look good. Hard to tell about some of the wiring though, in this or the RATT, because the image is not very clear. Some of the offboard wiring solder joints on the RATT look suspicious. That makes me want to see the solder side to see how it looks.
Also, I’m not sure what gauge wire you’re using but it seems to be about the thickest I’ve ever seen on these builds. 24 gauge is typical, and 22 gauge is fine but not needed. At a glance, yours look like 20 or even 18 gauge. Electric guitar pickup wires are 42 gauge–not suggesting that is sufficient for pedal wiring, but that’s where your signal begins and is a tiny fraction of 24 gauge. If you’re using anything thicker than 22 gauge, I’d consider downsizing. The smaller gauge is easier to work with and easier to solder.
These wires don’t look huge like the ones in your Muff’n but they look like balls sitting on top of pads, not all shiny, and definitely looking like someone put the hershey kiss in their back pocket on a hot summer day. Could be the photo, but I’d re-flow EVERYTHING.
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