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I’m not getting a reading when I go to set the gain trimmer, so then I decided to add some power to see if anything would happen, and the power led will light up for anywhere from 5 to 10 seconds and then slowly fizzle out.
Michael,
It seems like your board has some serious issues. My guess is that they are related to solder joints…possibly some bridged joints somewhere. So don’t power it on until we can get it checked out.
It would be helpful for me to see some detailed, in focus pictures of both sides of your board. Showing as many solder joints as possible (lift the pots up to show the joints under them). I might be able to see something that is causing the problem.
As far as getting “OL” on your meter… Most meters use “OL” (which stands for overload) if it can’t get a proper reading or the reading is too high for it to display. Make sure the battery in your meter is good and it’s working correctly (and the leads aren’t broken). Make sure the meter is set to read resistance. If it still is giving an “OL” when you measure TP5 and 6 it means that it is measuring infinity, which is an open circuit, so make sure the gain trim pot is soldered properly.
-Brach
Ok thank you. First I would just like to say that I would definitely say I’m a beginner. I have made some fuzzes and a treble booster, but they are super simple and I’ve never tried anything near this complicated. I’m still perfecting my soldering method, which isn’t great really, so I’m sure I’ve probably bridged something somewhere. Also I noticed in the build sheet what it said about overheating the op-amp. At first I don’t think I was using good enough solder, as it was taking way longer than 2 seconds to get it to melt. I have since found some solder that melts much quicker, but I’m worried I did damage the TLO74. I was about to order one along with a socket to maybe not have that problem again. How exactly can I send you some pictures?
Thanks for giving the Quaverato a go. If nothing else, I’m sure you’ll learn a lot about assembling pedals.
Do you know what kind of solder you were using and what kind you switched to (you could send pictures of that too)? It sounds like your original hard-to-melt solder might have been lead-free solder. That stuff is really hard to work with and I don’t suggest using it unless you have a lot of experience soldering. The way you were describing the solder that ended up using sounds like lead/tin solder. It’s much easier to use, but it doesn’t mix too well with lead-free solder. It’s hard to get good solder joints when both types of alloys are used. The type of solder you use is actually pretty important in helping you have a successful build.
If the solder was taking longer than 2 seconds to melt then your soldering iron wasn’t hot enough. Different solder alloys melt at different temperatures.
You might have damaged your TL074, but probably not. They are more robust than the manual makes it sound. The fact that you were conscientious of that makes me think it’s probably fine.
Google drive (or some other file/photo sharing site) is probably the best way to share the photos.
Let me know about the photos.
-Brach
I kno the solder is leaded, but the stuff I was using first was just some cheap solder that was in a little clear tube with a black lid that i bought at harbor freight. It’s probably just not very good quality, then I remembered I still had some leftover from a previous build kit, and started using it. It worked so much better. I’ll send some pics as soon as I get home from work. Thank you for your help.
I think that original solder from Harbor Freight might have been for plumbers to sweat pipes with. That stuff either has no flux in it or what they call “acid core flux” which is really corrosive to circuit boards. Hopefully it didn’t have any flux in it. The solder that is designed for electronics has rosin core flux in it. There is a “proper” ratio of flux to solder to get the solder to flow really well, so if your original solder didn’t have flux in it, it may be better to suck off the solder from most of the joints and re-flow them all with the good solder. You may have better luck getting this thing to work that way, and it will stay working longer with better solder joints…they will be less likely to get oxidized and crack.
-BrachThanks for the photos you emailed us. Unfortunately, due to the resolution and the focus of the photos I wasn’t able to see too many close details of the board. From what I was able to see, a good number of the solder joints still need to be flowed better. Good solder joints don’t have any sharp edges because those are the places (due to capillary action) that the flux won’t cover. You need flux to cover all the joint because it acts as a sealant against oxygen and moisture. If oxygen can penetrate the solder joint, then it will become “cold” and eventually crack. So that’s why good solder joints are important to have. After you re-flow the joints go over the board really well (with a magnifying glass) to look for tiny flecks or balls of solder that could be shorting together some pins. Sorry, I know this work is tedious, but it has to be done if you want a good working pedal.
With the LED fading out…another thing to make sure is that the paper underneath the pots don’t have any punctures in them otherwise it could cause a short, which could cause this problem.
Were you able to have any better luck with your meter? Were you able to measure the resistance between the test points?
-Brach
Unfortunately, no, I’m still not getting any readings on the test points. I have a brand new “Klein Tools” auto-ranging digital multimeter so I know it’s not my meter. I just think it’s like you said, there’s some serious issues on the board somewhere. I also looked up the harbor freight solder after what you said, and while it isn’t the plumbers type of solder that you mentioned, it is actually unleaded, which I had no idea about. I thought it was a lead based solder, so that is definitely why it was taking so long to melt. So, as tedious as it may be , I think I’ll just have to re-solder the whole thing. Kinda sucks, but it’s ok. Should I take the pots back out completely?
Are you able to get any reading when you measure across the trim pot’s solder joints, not test points?
If not, are you able to get any reading when you touch the 2 meter probes together?…you should be getting 0 resistance.
You probably don’t have to remove all the pots, if you can just suck off most of the solder, that should be sufficient.
-Brach
I was able to set the gain to 40k, and I think I figured out the problem. Pretty sure the op-amp is in backwards. I’m an idiot. I just noticed the notch on top is on the left side, but the outline underneath shows the notch on the right.
If you still have my pictures, one of them shows the 14 pin with the notches opposite each other
Is it ok if I just order one from somewhere? There’s no way I’ll be able to get it out without damaging it. I may just get another one and socket it.
Yes, that would do it! I didn’t even notice that…I was so focused on looking at the solder joints! Good noticing. Chances are, the opamp has broken now, so you do need to replace it. Please follow the steps in this blog to remove it, as to keep your board from getting damaged: https://zeppelindesignlabs.com/the-easy-way-to-remove-dip-ics/
You can order a new IC and socket from https://www.taydaelectronics.com/
Tayda is a good place to get all kinds of pedal parts at a reasonable price.
On a side note, I’m glad that you got the trim pot set.
-Brach
Thank you. The trim pot was another bonehead move on my part. For some reason when you switch to the ohm reader on my multimeter, it goes to a weird mode that just wasn’t reading correctly. I hit the mode button and it switched to “auto” mode and it started working perfectly. Again, bonehead noob move. I will let you know what happens after I switch out the IC. Thanks you again.
