1) Project - Lowrider
2) Problem Description - Sound is more of a tone control coming from UOCT1, DOCT1, DOCT2. No octave. CLEAN pot functions as it is supposed to. Turning UOCT1 down acts a volume control. Trim pot does nothing.
3) Steps Taken -
- Verified no solder bridges
- Confirmed board has power - Pedal works on bypass and engaged. Board has power and is outputting sound
4) Substitutions -
- followed recommendations of build sheet for "leaving C12 off, and using a 1n instead of 10n for C10" I put jumper wire in place of C10. Hmmm, Could this jumper be the issue ??? Just realized, Should I have left the spot empty?
- Did not have 160K for R55 so used (2) 82K in series
- Did not use Small Bear CD4013BCN used CD4013BE from Mammoth
C10.
When I get home tonight I plan to check voltages and compare to the readings from a working LowRider I found in another post. Regarding this, what are the little probe points designed on the board supposed to read?
I dont think its the ICs, I used both CD4013BCN and CD4013BE to see if any difference and there was none.
Did you mean jumper wire in C12?
get rid of the jumper and see what happens.
i think thats likely an issue
Quote from: Hangingmonkey on July 23, 2012, 02:13:22 PM
I dont think its the ICs, I used both CD4013BCN and CD4013BE to see if any difference and there was none.
Did you mean jumper wire in C12?
Yes sorry, jumper wire in place of C12 not C10.
Ditch the jumper. Just had a look at mine and the pads are unpopulated.
Yeah, the jumper at C12 is dumping all of your upper octave signal to ground and providing a short path to ground (through the upper octave pot and R49) for your clean, down 1 and down 2 signals, leading to it working like a volume control.
I will snip it out when I get home and report out. I appreciate the responses, thanks all. Thanks for confirming Hangingmonkey that yours is unpopulated.
Also , thanks mgwhit for explaining the "why" behind what's going on by having the jumper there. I was looking at the schematic trying to think through what having the jumper there would do. And that all makes perfect sense.
Clipped the jumper at C12. It appears to be working but it sounds like garbage. The upper octave is distorted and fizzy beyond belief. Setting the trimpot as described in the documentation does nothing. Regardless where I turn it there is no difference It is fuzzy at max, mid and min.. The lower octaves only appear to exist as added bass response and don't activate unless the upper octave is turned up at least a little. It sounds nothing like the demos I have heard. It's just farty and fizzy. It's more like a bad fuzz pedal than octave. ???
Holy Crap!!! I was just checking voltages across ICs when all of a sudden C22 just popped it's top. Spitting ooze. Luckily I had glasses on cause it was big. It was a 25v cap. What the hell is going on??? Aw shitty, looks like the cap was reversed. :'( . Well at least I have something pointing me to the problem...
Fixed the flipped cap, and sounds just like it did before.
Next step - Did a comparison to nzCDog's working voltages from this thread...
http://www.madbeanpedals.com/forum/index.php?topic=5239.0 (http://www.madbeanpedals.com/forum/index.php?topic=5239.0)
There are are some differences that I have highlighted. At this point I am uneducated enough to understand what might be causing them. Any help anyone???
IC1
1. 5V 5.04v
2. 5V 5.04v
3. 4.9V 2.48v
4. 0V 3.01v
5. 4.5V 5.04v
6. 4.99V 5.04v
7. 5V 5.04v
8. 9.1V 9.33v
IC6
1. 5V 5.04v
2. 5V 5.04v
3. 9.1V 5.01v
4. 5v 9.32v
5. 5V 5.04v
6. 5V 5.02v
7. 5V 5.04v
8. 5V 5.04v
9. 5V 5.04v
10. 5V 5.04v
11. 0V 0v
12. 5V 5.02v
13. 5V 5.04v
14. 4.86V 5.23v
Q1
D 9.1v 0v
S 5.32v 4.92v
G 4.3v 2.5v
IC1 - pin 4 is supposed to be tied to ground, and therefore 0 volts.
IC2 - pin 4 is supposed to be tied to 9 volts. Pin 3 is supposed to be tied to Vr, or roughly 5 volts.
Q1 - drain is supposed to be tied to 9 volts.
Trace your soldering, something is bridged, or something is not connected in the power distribution.
Pulled out the loupe and I've gone over the board at least 4 or 5 times, I cannot see any bridges. This is haunting my dreams. I get what you are saying alan just can't find it. Would Q1 being bad cause my voltage readings?
Don't get hung up over your IC6 voltages -- yours appear to be correct -- but alanp is right about IC1:pin3 and your Drain on Q1. My best guess: cold solder joints.
If IC1:pin3 were properly connected to ground, you would have 0V there, but you don't and other ground points appear to be okay. So there's either a cold joint or a broken trace cutting it off from ground.
Likewise with Q1:drain. Other +9V points have correct voltage, but this one point has 0V. Either a cold joint or a broken trace.
Retouched nearly every joint that could be suspect. My voltages now look very similar. But the sound is absolutely 100% the same. Just like I turned the treble down and turned up the bass. I'm attaching a pic too. Maybe someone might see something I'm not.
Working Mine
IC1
1. 5V 5v
2. 5V 5v
3. 4.9V 2.48v
4. 0V 0v
5. 4.5V 3v
6. 4.99V 5v
7. 5V 5v
8. 9.1V 9.3v
IC6
1. 5V 5v
2. 5V 5v
3. 9.1V 5v
4. 5v 9.3v
5. 5V 5v
6. 5V 4.75v
7. 5V 5v
8. 5V 5.1v
9. 5V 5v
10. 5V 5v
11. 0V 0v
12. 5V 5v
13. 5V 5v
14. 4.86V 5.1v
Q1
D 9.1v 9.3v
S 5.32v 4.9v
G 4.3v 2.5v
Did you mention what transistors you used?
Q1 - j201
Q2, Q3 - 2n5457
Well, looks like this one might be sitting on the shelf for a while. I'm clueless and bummed that I can't get this working. :(
To be fair, you found three significant problems in one day, which is (a.) good progress, and (b.) an indicator of how complicated a board of this size can be. Based on your description of the problem, you've probably got more than one error left. Definitely take some time away from it -- no sense working on a hobby that is supposed to be enjoyable when you're frazzled. When you do come back to it, consider using a signal probe. Good luck and let us know how it goes!
I'm a little OCD about projects I get working on sometimes and can't let stuff go. After thinking... My next step is to socket the trannys (something I normally do, but for some reason did not this time.) I'll try a few different ones to see if it makes any difference at all.
Woot! Problem solved! ;D ;D ;D I went back and socketed Q2 and Q3. For some reason the 2n5457s that were spec'd out just did not work in my build. I went through 12 different tranny types to find what I liked best. The top 3 were 2n5088, BC549, and MPF102.
The winner... MPF102. Although a little lower gain than the other 2, it was by far the clearest tracking of the lot. Only caveat is that while mostly cleaner, it appears to exhibit a slightly quicker note decay. This becomes more obvious with staccato palm muting. Another note; with the CLEAN turned all the way down and DOCT1 and DOCT2 turned all the way up the sound has a more ring mod like quality to it. Give them a try if you have some and you socketed your board.
In case anyone wants to know I can do a full report on all the trannys that I tested and my notes. The one thing I did not try was mixing and matching different values between Q2 and Q3. Some later day perhaps.
Thanks to you all for helping me through this difficult build!
Lessons learned - always socket trannys and any other components listed with alternates.
Wow. I didn't even know that non-JFETs would work in those positions. Cool to know. Glad you got it working. Have fun!
Quote from: GhostofJohnToad on July 26, 2012, 01:48:34 AM
In case anyone wants to know I can do a full report on all the trannys that I tested and my notes. The one thing I did not try was mixing and matching different values between Q2 and Q3.
GhostofJohnToad-
I'll be starting a LowRider soon, so this information would be very useful!