Hello,
I've recently built Egodriver and run into a problem... The pedal's working for about 5-10 seconds and that just runs out of volume. I've checked the soldering it seems fine to me, I've doublechecked the values of caps, resistors, pots, actually everything... The thing I noticed when I'm playing in LED clipping mode only one is "shining"? Maybe there's a problem?
Any suggestions?
Thanks
What type of LED are you using there? And, did you follow the instructions on how to correctly hook those up (with a jumper wire)?
I've jumpered them like it's shown in the .pdf file.
I used this type of LEDs => http://www.banzaimusic.com/LED-5mm-white-ultrabright-1000mcd.html (http://www.banzaimusic.com/LED-5mm-white-ultrabright-1000mcd.html)
Does the problem occur only when you have the LEDs selected or does it happen either way?
Yeah it occurs either way.
Sounds like the input to one of the stages is drifting up toward the rail or down to ground. That would explain why only one LED is lighting up, and also why the sound fades out.
It might be hard to check voltages for troubleshooting as the meter will complete the circuit, but if you have access to a multi-meter, can you provide the voltages at all the pins on the IC with respect to ground?
Sorry no access to a multi-meter, any other option? Man I want to get that thing start working! :)
Can you provide a couple of pics of your build? We'll need to do some guesswork since we don't have voltages. Pics may help in diagnosing the problem.
I've shot some pictures, if there are any different or closer look you want to get, tell me I'll provide new pictures.
(http://www.shrani.si/f/1c/105/1CtM9mbl/dsc02815.jpg)
(http://www.shrani.si/f/2R/iR/19iPm1U0/dsc02816.jpg)
(http://www.shrani.si/f/M/XN/151t1oeD/dsc02817.jpg)
(http://www.shrani.si/f/d/127/1kNQFqrX/dsc02818.jpg)
(http://www.shrani.si/f/1u/hR/28f4HWIC/dsc02819.jpg)
Okay, from what I can tell it looks like the LEDs are hooked up correctly. I think what you should do first is gently apply your heated iron the the solder joint where your wire connects from the LEDS to R3 on the left side of the board. Lift that wire out of place to disconnect it from the bias voltage. Now try testing the build out again and flip the switch to the other side (the side that uses the 2n7000 transistors for clipping). Do you get solid signal now, or does it continue to cut out?
OK, I'll try to do just that, when I get to my solder kit and will report right back.
I did what you told me, and it actually worked for like a minute and it went right off again as soon as I wanted to reply :/
And I noticed something funny when I roll volume knob all the way it gets no buzzer... So it's totally quiet when on 0 and fully open!?
Wow, it seems like there's a big problem going on there.
It sucks, but really the only thing we can recommend is that you go over it with a fine tooth comb again and again.
- Check all your parts are the correct value and are oriented correctly.
- Check all your soldering joints and resolder any that look suspicious.
- Use a DMM to check EACH of your joints connects ONLY to the parts it's supposed to. Use the Schematic and pencil in check marks. This way you can find a part that may be connecting to ground that may not supposed to, or a part that's not connecting where it is supposed to.
Using an audio probe is less helpful in this particular instance because it seems more like you have a power issue. I think you have a leak to ground or a misbiasing issue, meaning that your power is getting to ground or is not dividing properly. It works for a short time because Caps charge up under power, then release the power in a regulated flow sort of manner. I think that's why you have a few seconds of operation, then it stops because something is happening that is breaking or disrupting your power flow. I can't verify that from here though, only you can.
We are here to help in some ways, but ultimately it has to be you that fixes the problem. Wish I could help more, as does Brian I'm sure.
jacob
Ok, I borrowed a multi-meter, so can someone help em with how should I measure voltage on IC as oldhousescott mentioned?
@jkokura: thanks for all the effort! I can see something is really wrong! >:( I'm working on it for like 3 straight days, but still no result and I'm not gonna leave it at that!
Can you please tell me what is a DMM, so I can check?
Nejc
DMM is a Digital Multi Meter
To measure voltage at the IC you place the red probe on a leg of the IC and the black probe on ground.
Do this for each pin of the IC. You can follow the datasheet for pin numbers http://html.alldatasheet.com/html-pdf/9333/NSC/TL082/36/1/TL082.html
Josh
So if I got that straight I have to charge PCB with 9V and start measuring? (Do I have to unsolder any of the components?)
Doing this thing first time so that's why I ask so much questions :-\
Will provide measurments on IC within this weekend.
Nejc
Yup, just power up with 9v and start measuring :)
Josh
The thing is I have an analog MM, so I think it would be better to have a digital one, right? :-\ So pins 4 is (around) 0V and pin 8 is around 9V? It's measurments I found in other topics.
No, an analog is fine.
Yes, 0v at 4, 9ishv at 8. Approx 4.5v at the rest.
Jacob
Analog is fine, just be sure you've got the selector set to the correct range (DCV) and make sure you're reading off the correct scale for your measurements. Also, make sure you're looking straight on at the meter face when you make the measurements.
OK,I've measured the voltages and clearly is something wrong :(
They go like this:
1 | 1,5V - 8 | 8,5V
2 | 1V - 7 | 1,5V
3 | 1V - 6 | 1,5V
4 | 0V - 5 | 1,5V
Nejc
EDIT: Something I noticed while trying to solve this major problem :( I rewired gain and volume pots because I thought there was the problem, so when I plugged in it's working but still "farty" sound coming out of it and still one of the LEDs is shining while playing. What I figured is really strange, I kinda connected (with my fingers ) all 3 pots and one LED started shining bit more and sound was coming clearer, the other LED still no response...
Does that ring any bells?
It looks like you've used incorrect parts or that you've got some connected poorly. It's really easy to mix parts up and install them in the wrong spots. I would do the following, even if you've already done it I would do it again:
Check you've used the correct part values.
Check you've used the correct part orientations.
Check you've used the correct wiring.
You could also have a part that's got a solder bridge, so check your soldering also.
Jacob
So I resoldered all of the parts , the orientation only matters for electrolytic and tantalum caps, right? Checked again all the values for resistors and caps, resoldered and checked the wiring for pots and switches it worked for like 5 minutes and than again it when all buzzy...
I've rewired whole thing... It's seemns to be working now, it still gets sometimes that buzzy sound but that because of the toggle switches which I guess melted somehow (they're some Taiwan cheap-ones). I still don't know where was the main problem maybe soldering or maybe even wires, all of them were replaced with "stronger" ones, or maybe after all the toggle switches... :(
Good job on getting it going! It sounds like something is making a bad connection to get that sound. Could be a bad solder joint like suggested or the switch could be melted and making bad contact inside like you said. Keep practicing you'll get better!
Since I'm done with my EgoDriver and all the troubles I went through I've learned quite a lot. Also thanks goes to you guys being patient with my troubles trying to get this pedal done... Again thanks!
I've got another question concerning my problem. So is it possible that because of the bad wiring of gain and volume pots voltages on IC were not right?? Because I've measured them again and now they're like they suppose to be approx. 4.5; 0; 4.5 and 9V (mine Vs are 4.4; 0; 4.4 and 8.85V)??
Thanks again and have a great day!
Nejc
8.85 pin 8 would be where you're starting from. That's your input voltage. If you use a battery that will slowly get lower, and if you use a power supply it could read 9 or 9.6 or whatever and will remain constant.
0V is ground, it's the opposite pole of your power source. Pin 4 should never read higher than that.
4.4V on the other 6 pins is to be expected because your starting with 8.85. This circuit, and many other overdrives, uses a combination of resistors and capacitors to divide the input voltage in half, meaning that you'd take your input voltage (8.85) and divide it in half (4.425, or 4.4 if you round) and that gets applied to the various parts of your op amp's gain stages.
Simply put, your voltages are perfectly fine, but would change if you changed your input voltage.
Jacob
I've measured voltages with Boss adapter, so is that OK concearning the voltages?
One question that bothers me: Is it possible that because of the bad wiring of gain and volume pots voltages on IC were not right??
Nejc
Quote from: jkokura on November 09, 2011, 05:06:05 PM
Simply put, your voltages are perfectly fine, but would change if you changed your input voltage.
Don't know about the 2nd question, but my guess would be that if it was a problem it would likely because something in the wiring was leaking your bias voltage to ground.
That 4.5V thing, where the voltage is divided, is usually called 'bias voltage'. Essentially, what it looked like was that the places where you should be seeing the 'bias voltage', around 4.5V, was somehow leaking some of it's power to ground, or to another area where it shouldn't. Maybe that was in the pots, but more likely it was on the PCB. A wrong part, a solder bridge, a cold joint - all of those could be the reason, and just as likely if not more likely than the pot wiring.
Jacob