Help needed with Boss CE-2 clone project

[pgosselin]

Hi all,

I've been a long-time lurker here, but have finally felt the need to join because, well, I'm stumped.

I've been building a Veroboard clone of a Boss CE-2 chorus pedal based off of this plan:

http://tagboardeffects.blogspot.com/2014/06/boss-ce-2.html

I've been building the third one down the page, the one without the daughterboard or the Madbean depth mod. I simply want the original CE-2.
Unfortunately, I made a horrible error. Two of my jumpers got pinched together underneath the IC4 socket. When I plugged it in, the 33 ohm resistor connected to the 9v supply fried (never had a part burn up on me before). Before I fried another resistor, I traced the 9v portion of the circuit to see where it had inadvertently connected to ground causing the dead resistor. That's when I found the jumper issue. I have repaired it and replaced the fried resistor.

Before I plugged it in again, I double checked the placement of all my parts. I did find one additional error. The 10K resistor (next to the 33 ohm one I fried) was not connected to the ground strip, but was connected to the strip below it. I have also fixed that error.

Now when I plug in the pedal for testing, I get a signal through the bypass. But when I engage the pedal, I get nothing. Not even a weak or distorted signal.

The LED is on and I have checked to see that the board is getting power. I am reading 9.41v where the 9v connects to the board.

I have even tried to audio probe the board and while the audio probe works in bypass, I get no signal before the board (not even at the hot input tab on the input jack, where usually I can get a signal) or on the board. I CAN get a signal through by touching the output tabs of the foot switch and the output jack.

The input tabs on the input jack and foot switch appear to be okay. I can get continuity from the hot tab of the input jack all the way to the input on the circuit board. So the wiring looks good that far. So I can't figure out why I can't pass the audio signal through.

I am at a loss as to what I did wrong.

Did my earlier problem also fried the IC chips? If so which ones?

Here are the readings I get from the pins of the IC chips:

IC#1 (JRC4558D)
1. 8.68v
2. 8.64v
3. 8.60v
4. 0
5. 8.60v
6. 8.68v
7. 8.68v
8. 8.60v

IC#2 (TL022CP)
1. 9.16v
2. 8.61v
3. 8.73v
4. 9.26v
5. 8.62v
6. 8.72v
7. 8.72v
8. 9.26v

IC#3 (MN3007)
1. 9.26v
2. 9.05v
3. 7.81v
4. 9.04v
5. 9.26v
6. 9.05v
7. 9.21v
8. 9.21v

IC#4 (MN3101)
1. 9.26v
2. 9.05v
3. 9.26v
4. 9.05v
5. 9.04v
6. 8.95v
7. 9.13v
8. 9.26v

And here are the readings from the 5 transistors (2N5088)

Q1
E 7.33v
B 7.62v
C 9.26v

Q2
E 7.81v
B 8.32v
C 9.26v

Q3
E 7.48v
B 7.84v
C 9.26v

Q4
E 9.26v
B 8.60v
C 8.62v

Q5
E 9.25v
B 8.47v
C 9.26v

Here is a link to a gallery with photos of the front and back of my Veroboard project as well as the schematic from Tonepad:
http://s1134.photobucket.com/user/pdgosselin/library/Boss%20CE-2

I have also used tone pad's parts list. If you need to access it, you can find it here:
http://www.tonepad.com/getFileInfo.asp?id=101

I would appreciate any helping insights that the much smarter people than me on this board can supply. (While I do enjoy these projects, I often feel like I am swimming in water over my head.)

And if you do see additional errors with my work, by all means, let me know.

Thanks in advance for any help and advice.

Paul

[Slowpoke101]

You are missing 0V on ICs 2, 3 & 4.
Resolder the outlined joint under IC4 and check the voltages again.

[pgosselin]

Slowpoke,

Thanks so much for the quick reply.

Great eyes noticing the poor solder joint. I have repaired it. But I am afraid to take readings at the moment

When I plugged in the circuit board to take readings, I smelled something beginning to burn. I immediately unplugged the board. Upon inspection, it looks like that same 33 ohm resistor is starting to burn up. I checked continuity between those two long traces under IC1 and IC4 and they are again connected somewhere.I've got a short circuit in there I need to find.

Dang it, I thought I had solved that.

Paul

[Slowpoke101]

The component that your are using as D3 is most likely a zero ohm resistor (a link). Yes, zero ohm links do exist.
Replace it with a diode and the short that you are chasing should disappear.




I didn't edit the image properly hence the excessive black borders...oops.

Oh yes, Welcome to the forum.

[pgosselin]

No worries about the black border, Slowpoke. I'm just glad to have the help.

You are correct, that is a jumper. As I researched this pedal, a lot of builders said that 12v zener diode was unnecessary if you had a regulated power supply. The diode is supposedly a relic from the days when Boss used a 12v unregulated wall wart.

But maybe the layouts of the people omitting it differed a little from this one?

Fortunately, I ordered 12v zener diode with the rest of my parts just in case. I'll swap the parts and see if that makes a difference.

Thanks again for taking a look at my post.

[thermionix]

I can't follow a vero layout nearly as well as a schematic, but there's a good chance that omitting that zener means just that, use nothing in its place rather than a jumper.  I would try snipping that out, see what happens.  If you want to replace it later, just use some component lead clipping (free!).

[duck_arse]

measure the resistance between pin 8 and 4 on the opamps, then, like therm says, snip that zero link, and measure resistance again. and if you are worried about voltsing up the IC's, just pull them from the sockets before you power on, and do voltage measures on the empty pins.

[pgosselin]

Thanks for the help Slowpoke101, Thermionix and duck_arse. I'm getting closer.

I went ahead and snipped the jumper and soldered in the zener diode. I had already done it last night before Thermionix and duck_arse replied. (But I came to the same conclusion as you all: if I was going to omit it, I didn't need to add the jumper.) As things stand now I have the diode in place so I'm sticking with that for now.

The results:
-- I am no longer cooking that poor little 33 ohm resistor, but the effect is still not working right.
--However, the good news is that before, I couldn't get a signal through. Now I am getting a barely perceptible one through one through when I touch the audio probe to the hot lug of the input jack and to the foot switch lugs. It's barely there, but it's there. At random, I touched the audio probe elsewhere on the circuitboard and got a regular level signal through. So that's progress.

If by looking at my IC chip and transistor readings you all can point me in the right direction to narrow my search for more errors, here's the NEW data:

IC#1 (JRC4558D)
1. 3.09v
2. 3.09v
3. 3.09v
4. 0
5. 3.09v
6. 3.09v
7. 3.09v
8. 9.18v

IC#2 (TL022CP)
1. 8.51v
2. 3.09v
3. 3.91v
4. 0
5. 3.09v
6. 6.37v
7. 3.16v
8. 9.18v

IC#3 (MN3007)
1. 9.19v
2. 4.71v
3. 2.45v
4. .614v
5. 0
6. 4.69v
7. 3.12v
8. 3.12v

IC#4 (MN3101)
1. 9.19v
2. 4.69v
3. 0
4. 4.71v
5. .224v
6. 8.38v
7. 2.51v
8. .614v

And here are the readings from the 5 transistors (2N5088)

Q1
E 2.31v
B 9.17v
C 9.19v

Q2
E 2.45v
B 3v
C 9.19v

Q3
E 3.09v
B 2.98v
C 9.19v

Q4
E 0
B .702v
C 4.06v

Q5
E 1.112v
B 3.07v
C 9.19v

Oh and, duck_arse, I am gong to sound like a complete idiot, but how do i measure the resistance between pins 8 and 4 on op amps? Do I set my multimeter to ohms and then put a probe against each leg? Do I do it with power on or off? I would assume off.

Once again, everyone, thanks for all the help thus far. And since there appear to be so many Aussies helping me, just so you all know, the first song that plays when I audio probe is AC/DC's "You Shook Me All Night Long." 

[Slowpoke101]

You are making progress - no magic smoke being emitted.

Q1 - its base voltage is far too high. Should be about 4.9V - perhaps shorted to its collector.

You do have to adjust the trimmer. A good starting point is to measure pin 5 of IC1 and adjust the trimmer for 5V.
Once you have corrected the Q1 problem and adjusted the trimmer, try to see if you can get audio through the pedal.
You must have the "Vibe" switch closed. This will allow dry audio to pass. If you have dry audio - good and now onto the next problem.

IC2 (TL022) which is the LFO doesn't seem to be working - according to the voltages you posted. Have a good look for any shorts or solder bridges in that area. Make sure that you have the Rate pot correctly installed and that it actually works. Pin 1 of IC2 should go from nearly 0V and up to 8V. The speed at which it does this depends on the rate pot setting.

If all is working now you can move on to the correct setting of the trimmer. Set the "Vibe" switch to open and see if you have any audio passing through - if you do, set Rate to midrange and Depth to maximum then adjust the trimmer so that the audio you are hearing is not too distorted but is still being modified by the delay effect. Easy to do with an oscilloscope but fiddly to do by ear.

If you still have problems measure all the voltages again and let us know.

Now for that link that you used as D3. If you look at the Tonepad parts list there is no D3. It is actually listed as D7 (11V zener). If you look at Tonepad's schematic you will see that D7 is connected to the main power rail (9V) and to ground (0V). If you replace it with a link you effectively short out the incoming power and release the magic smoke. So it would have been better to have nothing installed in the D3 position. You don't really need to have the zener but it can save the MN3007 from frying if something does go wrong.

Good job on AC/DC. A great band.

[pgosselin]

Holy cow, Slowpoke101. You can tell all that from my data! That will take me a few night to work through all of that.

Since I eliminated the vibe switch, I may have to wire one up temporarily.

Thanks for all the help!

[DIY Bass]

Also, have you replaced that 33 ohm resistor since you last overheated it?  Even if you didn't smoke it I would be suspicious that it is no longer at the proper value.  At the very least check it but I would be replacing it if you haven't already.

[duck_arse]

I'd like to look at your photos, but, well, botophucket. and scripts. and viva, whatever that is, eats my pc.

when measuring resistance, always power-off the circuit. the meter itself puts some known volts across its probes, and reads the result thru the resistor, so if you go adding stray volts here and there having the supply on, all your results will be wrong. I wanted the opamp pins cause I couldn't see the circuit, so opamp pins 8 and 4 [while the IC is still fitted, tho across the empty socket pins will show the same result] would have shown 0R while the link was there, and "some number larger than 0" once it was removed. the change in the reading was what I was driving towards.

and from your data - it's easy - your Vb connects to pin 5 of IC1, so we know that voltage. it also connects to the base of Q1 via 470k, so the base should be a little lower than the Vb at pin 5, whereas yours is sky high, close enough to the collector voltage as no matter. pointing to a short.

all those 3V09 voltages on IC1 should track the trimpot as you adjust it, once you've fixed the short.

[pgosselin]

Also, have you replaced that 33 ohm resistor since you last overheated it?  Even if you didn't smoke it I would be suspicious that it is no longer at the proper value.  At the very least check it but I would be replacing it if you haven't already.

Yes, I did. Even with minimal charring, I didn't trust it.

Thanks for double checking me, DIY Bass.

Paul

[pgosselin]

You are making progress - no magic smoke being emitted.

Q1 - its base voltage is far too high. Should be about 4.9V - perhaps shorted to its collector.

You do have to adjust the trimmer. A good starting point is to measure pin 5 of IC1 and adjust the trimmer for 5V.
Once you have corrected the Q1 problem and adjusted the trimmer, try to see if you can get audio through the pedal.
You must have the "Vibe" switch closed. This will allow dry audio to pass. If you have dry audio - good and now onto the next problem.

IC2 (TL022) which is the LFO doesn't seem to be working - according to the voltages you posted. Have a good look for any shorts or solder bridges in that area. Make sure that you have the Rate pot correctly installed and that it actually works. Pin 1 of IC2 should go from nearly 0V and up to 8V. The speed at which it does this depends on the rate pot setting.

If all is working now you can move on to the correct setting of the trimmer. Set the "Vibe" switch to open and see if you have any audio passing through - if you do, set Rate to midrange and Depth to maximum then adjust the trimmer so that the audio you are hearing is not too distorted but is still being modified by the delay effect. Easy to do with an oscilloscope but fiddly to do by ear.

If you still have problems measure all the voltages again and let us know.

Now for that link that you used as D3. If you look at the Tonepad parts list there is no D3. It is actually listed as D7 (11V zener). If you look at Tonepad's schematic you will see that D7 is connected to the main power rail (9V) and to ground (0V). If you replace it with a link you effectively short out the incoming power and release the magic smoke. So it would have been better to have nothing installed in the D3 position. You don't really need to have the zener but it can save the MN3007 from frying if something does go wrong.

Good job on AC/DC. A great band.

Slowpoke101,

Well, I scraped between the copper strips  near Q1 and there must have been a short I couldn't see with my magnifying glass. I got the  base voltage down significantly.  It was reading in the high 3s before I adjusted the trimmer to as close to 5 as I could get it. Now, Q1 reads as follows:

E = 4.01-4.13
B = 4.80-4.97
C = 9.11-9.15

I can't seem to get a steady voltage on Q1 or the trimmer, They kind of dance around between the numbers above. Same is true of the trimmer, it's dancing between 4.89 and 5.03. Is that normal?

I plugged in the guitar and tried to get a signal through, but no dice. Nothing's getting through.

Any thoughts?

Too soon to move onto IC2.

Thanks again for the help

Paul

[Slowpoke101]

Progress. This is good. At least the voltages on Q1 are now correct. Veroboard can be a pain for hiding shorts and broken traces. As time consuming as it is, testing each track for continuity and adjacent tracks for shorts can find problems faster than visual inspection.
From a prior post of yours I note that you have an audio probe (or something that can be used as one). You will need it shortly.

From the solder side picture of your board the soldering around the IC1 area looks as if it could be a bit better. Pin 1 of IC1 does not seem to be soldered properly and some adjacent solder joints look to be almost touching. Go over the area and make sure that it as all OK.

You don't need to install a "Vibe" switch - The original CE-2 didn't have one and the circuit works fine without it. Just install an insulated wire link from "Vibe Sw1" to "Vibe Sw2". Now check to see if dry audio passes through the effect. If it does - good, then proceed with the rest of the troubleshooting. If no audio passes test what audio signal is present on Pin 2 of IC1 and then Pin 1 of IC1. Both pins should have audio on them. Then test for audio on Pin 6 and Pin 7 of IC1, again audio should be present.
Let us know what the results are.

The dancing voltage from the trimmer...This may actually be good news (in a way). See if the speed that the voltage varies at  relates to the setting of the Rate and Depth pots. If it does vary then the LFO may be working.

The reason why we like people to post their voltage readings is that the voltages can tell the story of what is possibly wrong. Along with a schematic and some pictures of the board it becomes a lot easier to help diagnose what the problem is. It can be a lot of fun to work out what is going wrong. It's even better when the problems are resolved and someone's project is working and they are happy.

[pgosselin]

Slowpoke101,

Here's where I am tonight.

1. I reworked all of the connections on IC1 and cleaned between tracks. Unfortunately, the copper has been lifting off my board right in that area, so I had to patch up a couple of the connections with some thin wire I have. I have checked continuity on each pin and it is good. I also used the multimeter to check to make sure there were no solder bridges between pins/tracks.

2. This is only the second Veroboard project I've done. Everything else has been either perfboard or circuit boards. My previous Veroboard project was Craig Anderton's phase shifter and it turned out great. So I thought I would try Veroboard again. This batch from Tayda does not seem to be as good as the last batch.

3. As for audio, I cannot get a guitar signal through. However, with my audio probe (which is connected to the headphone jack on an old MacBook), I can get audio through pins 2 and 6 of IC1. I cannot get audio through pins 1 and 7.

4. I also probed the input wire and the first capacitor and resistor, I am getting audio signals through on them, but very faintly. The audio on Pins 2 and 6 are a decent volume.

5. Why is it I can get audio signals through with my audio probe, but not with my guitar? That is very strange to me.

6. I have the vibe switch permanently closed. I realized I didn't need a switch last night. Per some instructions on the website where I got the Veroboard layout, the author said if one didn't want the vibe function, you could just move the 47k resistor at Vibe Switch 2 to the top row above IC1, bridging the cut. This effectively closes the switch.

This project is proving far more difficult than I expected.

Thanks again for all the help.

Paul

[Slowpoke101]

You may not feel that you have but you have made progress.

The mod with moving the 47K resistor to the track above IC1 is elegantly simple. Better than running a wire link from one side of the board to the other.

Now, audio on pin 2 and 6 of IC1 but none on pin 3 and 7. An audio probe using the "headphone" socket on an old Mac...I assume that you mean the mic connection and that you are using the Mac as an amplifier. Make sure that your probe has a 0.1uF capacitor in series with the probe connection, otherwise any voltage that the Mac may send to a microphone may upset the circuit under test and vis versa. Audio on pin 2 means Q1 is working. Audio on pin 6 means that audio is coming out of pin 1 and making its way to pin 6. I suggest that you check for audio on the output lead were it connects to the board.

Buying quality Veroboard can be haphazard at best. The cheap boards do the job but really don't stay together when you rework any connections. Veroboard is (or was) a brand name product and the original board was of excellent quality but not cheap. A lot of the cheap stuff is OK but a lot it is not. No real control on what you get.

Once you get your audio probe installed with a 0.1uF coupling capacitor and found audio on pin 1 of IC1, see if there is any audio on pins 3 and 8 of IC3 (MN3007). Let us know how you go.

[pgosselin]

Once again, thanks Slowpoke101.

I am already using an audio probe properly constructed with the .1 uF capacitor, I built it with a 1.8" male plug on the far end that goes into the headphones output jack on my MacBook (not the mic). That way, I can play music in iTunes and output it through the audio probe, touching the .1 uF cap to the various parts while the other wire attached the probe to the ground lug of the effect.

So the probing of pin 6 shows I have audio coming out of pin 1? Yet, I am unable to detect audio at pin 1 with the audio probe. Maybe I better test that area again and give it another look-see.

I will check for audio on the output lead wire where it connects to the board as well as pins 3 and 8 of IC3 tonight after work.

Thanks again,

Paul

[bluebunny]

Erm, the audio probe is intended to be used the other way around: you plug it into an amplifier and probe your circuit listening for signs of the audio which you're delivering to the input jack (which might be a guitar or some other kind of sound generator).

[pgosselin]

Bluebunny,

Omg, I've been doing it backwards? Dang, even my backwards probe has helped me find some problems.

Definitely will be retesting tonight...the proper way.

Paul