Hi everyone, I've just finished building an Echobase and am stumped by a problem I'm experiencing. Let me preface this by saying I just joined this great community last month, and that this is my first-ever circuit build. Since the first day, I've been eating up all the wonderful information found here and have been so impressed with the generosity of everyone in this forum. A special thanks to Ian for this great project.
When I felt up for the challenge, I read and re-read this entire thread, absorbing the knowledge and noting various issues folks had with their builds. I also practiced my soldering skills by building a passive A/B switch, and a TB Dual Looper, my first two stompboxes. Needless to say, the last few nights have been incredibly frustrating as I have tried to troubleshoot the problem with my build. Any tips and insight would be appreciated.
1.What does it do, not do, and sound like?
With effect on, and all knobs set to minimum, I can hear the dry signal fine, which means there is no problem with the TL072's.
Also, with Time pot at 12o'clock, and everything else at minimum, I hear only the dry signal. This is a good thing.
After turning up the Level, and Time pots (and leaving others at minimum), and a quick guitar strum, I hear a very, very faint repeat of the chord, but I really have to strain to hear any semblance of what I played. Any repeats after that (if I can hear them) are incredibly distorted. In fact, no setting enables me to hear what I consider an actual set of clean, delayed repeats, at least nothing anywhere near Ian's original sound clips. One other way to describe it is that whenever I play a note, I can tell that there IS a delay, and that the Time, Feedback, Depth, and Speed knobs function if I turn them, but I don't hear what I played being repeated or affected in any clear fashion. It's like my note gets thrown down the side of a waterfall and I'm listening and listening, but hear only a faint echo, which quickly gets overcome by noise from all sides. Increasing the Level knob only turns up the noise(and of course, after 2 o’clock, the whole thing melts into self-oscillation like a Roland Space Echo - I'm assuming this is ok, bc it's part of the Echobase appeal to me). All the while, the clean signal is clearly audible throughout this. Also, the bypass switch works, and the tails/Boss switch works too. I have seen others post a similar issue as mine, but I was not able to fix it by checking for shorts around the pot connections.
2.Source of the circuit (URL of schematic or project) = I used John Lyons' PCB, based on anonymousfacelescoward's layout. All jumpers confirmed. No solder bridges that I could detect. It all fits into a 1790NS enclosure.
3.Any modifications to the circuit? NO.
4. Any parts substitutions?
Parts all stock except for:
a) 78L05 instead of 7805
b) 2N5087 instead of BC560
c) TIME POT: 50k lin instead of 47k lin
Note: I looked up each transistor's datasheet and confirmed that I placed the E,B, and C in the correct sockets, remembering that the orientation for 78L05 and 2N5087 are both opposite from the 7805 and BC560, respectively, in the layout.
5.Positive ground to negative ground conversion? NO.
6. Out of circuit battery voltage => USING 1SPOT 9V pedal power supply.
7. Voltage at the circuit board end of the red battery lead = around 9.5
8. Voltage at the circuit board end of the black battery lead = around 0
9. Voltages: Oddly, voltages on the PT2399, the two TL072's, and the 2N5089 all match the voltages provided by Ian. The differences appear solely with the 4066, as you'll see:
U4 - CD4066
--PIN - (Ian’s Voltages)
P1 2.88 (4.6)
P2 2.88 (4.6)
P3 .03 (.4)
P4 .02 (.4)
P5 0 (0)
P6 .44 off - 2.88 on (0.45v off 4.5v on)
P7 0 (0)
P8 8.45 (9)
P9 nothing (this pin leads to the LED) (3v on 0.32 off)
P10 2.88 (4.6)
P11 2.88 (4.6)
P12 7.78 on (8.5)
P13 4.92 on (8.5)
P14 9.5
Is this something really obvious that I’m missing? I just don’t understand how my readings are almost half of what they are supposed to be.
I know the voltage regulator works, since the other IC’s show 5.04v. Is there a chance that the 4066 is malfunctioning? Why would it only read 2.88v if everywhere else on the circuit appears to be getting the proper voltage? Should I change the voltage regulator? Does it have any relevance at all?
I haven’t had a chance to systematically troubleshoot with the audio probe (I have a 21-month son and pregnant wife so I can only work on this a couple hours a night) but will do so ASAP. I would also post some pics but am at work and may do so later if it would help.
Thank you anyone who can offer any insight for this frustrated noob. Through the distortion, I can almost hear the glory of the Echobase.
