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DIY Stompboxes => Building your own stompbox => Topic started by: znanjeiimanje on September 13, 2021, 12:10:21 PM

Title: Boss CE-2 troubleshooting
Post by: znanjeiimanje on September 13, 2021, 12:10:21 PM
Hello everyone, long time lurker but my first post on here.

I have a CE-2 that has started to drive me crazy. When it's plugged in and on, you do hear a slight change of the tonality vs the dry signal but not something you could call chorus. Basically there is no effect.

A couple of days ago I dismantled it and was about to change all the capacitors and left it open, some components touched each other and it started working, but with loud ticking. Since it was open on my workbench, when I moved it it stopped working.

I changed all the capacitors, nothing.

Re-confirmed all solder joints on the board, nothing.

Took out MN3001 and MN 3007, soldered them back in, nothing.

Then I got around to measure voltages across the board and all was fine except the TL022.

The readings I got were:

1 0
2 0.6
3 4.0
4 0
5 0.26
6 4.0
7 0.6
8 9.0

Where they should be:

1 VAR
2 4.5
3 VAR
4 0
5 4.5
6 4.5
7 VAR
8 9.0

I have tried swapping the TL022 to TL072 (the only one I could find) and it didn't change anything.

Anyone got any idea where I could continue looking as it doesn't seem to be the chip itself?
Title: Re: Boss CE-2 troubleshooting
Post by: CheapPedalCollector on September 13, 2021, 01:30:29 PM
Voltages there are way wrong, usually indicating a bad op amp.

check VR3, R27 and R28 as well. Pull the chip and put in a socket so you can measure the voltages with the chip out of the circuit and see if VREF is 4.5v or so volts.

check Q1, Q2 and make sure they aren't blown/shorted, and Q3 to make sure it's working properly.
Title: Re: Boss CE-2 troubleshooting
Post by: znanjeiimanje on September 13, 2021, 04:28:09 PM
Thanks a lot for the help.

I just checked and it's as follows:

- VR3 Seems to work fine and gives me 10k
- R27 and R28 I get 4.7k on both
- Q1, Q2, Q3 seem to be in order
- I pulled the chip and no way I can get 4.5 on the socket

Any other ideas would be appreciated.
Title: Re: Boss CE-2 troubleshooting
Post by: Kevin Mitchell on September 13, 2021, 04:40:20 PM
I think the previous suggestion was to breadboard the opamp to test it.
Use two identical resistor values (like 2 10k resistors) between the power rails. That will give half of the supply voltage in-between them. Place that node on the + input of the opamp, short the - input to the output. This makes it a voltage reference buffer. So if you get 4.5v (half of a 9v supply) on the + input but something else on the output then you know the opamp is bad.

On the subject of what you did already, adjusting VR3 should allow you to dial in your voltage reference. Pin 3 of IC1 goes straight to that voltage reference and I see you wrote 4 volts, which appears normal. Though that voltage has nothing to do with determining if an opamp is bad or not. Extract and test externally.

Aaaaand welcome to the forum!!
Title: Re: Boss CE-2 troubleshooting
Post by: CheapPedalCollector on September 13, 2021, 11:06:01 PM
OK, so check that you have ~9V at one end of R27, if you do then it's possible that C18 is shorted/out of spec. If you don't then start at D7, R52, C29 and C30. It's also possible Q9 is dead, try to avoid pulling parts unless you have to.

Also are you trying to run this on a power supply or battery. If power supply and it needs an ACA adapter you can do the voltage mod for it, or use a 12V supply. I suggest troubleshooting using a battery.

Troubleshooting is about isolating the problem by ruling things out. Also, use a magnifier check for bad solder joints and cracks in the traces.
Title: Re: Boss CE-2 troubleshooting
Post by: znanjeiimanje on September 14, 2021, 08:01:24 AM
I think the previous suggestion was to breadboard the opamp to test it.
Use two identical resistor values (like 2 10k resistors) between the power rails. That will give half of the supply voltage in-between them. Place that node on the + input of the opamp, short the - input to the output. This makes it a voltage reference buffer. So if you get 4.5v (half of a 9v supply) on the + input but something else on the output then you know the opamp is bad.

On the subject of what you did already, adjusting VR3 should allow you to dial in your voltage reference. Pin 3 of IC1 goes straight to that voltage reference and I see you wrote 4 volts, which appears normal. Though that voltage has nothing to do with determining if an opamp is bad or not. Extract and test externally.

Aaaaand welcome to the forum!!

Thank you very much for the welcome. I did exactly what you wrote step by step and it appears normal. In addition I have swapped it with a new OP amp and all seems fine.

OK, so check that you have ~9V at one end of R27, if you do then it's possible that C18 is shorted/out of spec. If you don't then start at D7, R52, C29 and C30. It's also possible Q9 is dead, try to avoid pulling parts unless you have to.

Also are you trying to run this on a power supply or battery. If power supply and it needs an ACA adapter you can do the voltage mod for it, or use a 12V supply. I suggest troubleshooting using a battery.

Troubleshooting is about isolating the problem by ruling things out. Also, use a magnifier check for bad solder joints and cracks in the traces.


I started with the R27 and indeed I do have 8.9V at one end. I took out the C18 and replaced it with a new one, but I still get the same result. Seems like the issue could be before R27.

Also, I'm always running things on batteries so this time I can't blame the adapter.
Title: Re: Boss CE-2 troubleshooting
Post by: CheapPedalCollector on September 14, 2021, 01:00:45 PM
OK then, measure Q9 in resistance mode of your meter. you should get 100ish ohms between Gate and Source, and more than a meg between Gate and Drain and also a couple megs between Source and Drain. Also check the diode connected to it.
Title: Re: Boss CE-2 troubleshooting
Post by: antonis on September 14, 2021, 02:54:36 PM
It's always better to talk with a schematic availiable.. :icon_lol:

(https://i.imgur.com/WvQ0gXU.jpg)
Title: Re: Boss CE-2 troubleshooting
Post by: Kevin Mitchell on September 14, 2021, 03:10:04 PM
After reviewing this thread again;

To rule out Q9 you could just check for the wet signal before it. If it's there but not pin two of IC1 then you'd know that's the problem.

My first impression is either the LFO is locked up or BBD or driver is dead.

Check the LFO;
Turn the rate and depth fully CCW and probe the DC voltage going to pin 7 of the MN3101 and see if it's shifting. May be too fast to notice - in that case check the frequency there to see if there's anything going on.

Check the MN3101;
Use a multimeter to check the frequency on both pins 2 and 4 (I compare these to bike pedals, one goes high as the other goes low - effectively driving the two channels of the BBD)

Check the MN3007;
Make an audio probe and listen for pins 7/8 on the BBD. I'm guessing there's no sign of the guitar signal there. Doesn't mean it's bad though - unless the previous steps check out.

Best to test in that order to rule things out along the way.
Title: Re: Boss CE-2 troubleshooting
Post by: znanjeiimanje on September 14, 2021, 04:30:39 PM
OK then, measure Q9 in resistance mode of your meter. you should get 100ish ohms between Gate and Source, and more than a meg between Gate and Drain and also a couple megs between Source and Drain. Also check the diode connected to it.

I tested it right now (in the circuit) and I get 340 ohms between Source and Gate, but I get nothing between Gate and Drain. Would this mean the transistor needs replacement?

After reviewing this thread again;

To rule out Q9 you could just check for the wet signal before it. If it's there but not pin two of IC1 then you'd know that's the problem.

My first impression is either the LFO is locked up or BBD or driver is dead.

Check the LFO;
Turn the rate and depth fully CCW and probe the DC voltage going to pin 7 of the MN3101 and see if it's shifting. May be too fast to notice - in that case check the frequency there to see if there's anything going on.

Check the MN3101;
Use a multimeter to check the frequency on both pins 2 and 4 (I compare these to bike pedals, one goes high as the other goes low - effectively driving the two channels of the BBD)

Check the MN3007;
Make an audio probe and listen for pins 7/8 on the BBD. I'm guessing there's no sign of the guitar signal there. Doesn't mean it's bad though - unless the previous steps check out.

Best to test in that order to rule things out along the way.

This I will try later tonight, I need to set up everything for the probe to work.
Title: Re: Boss CE-2 troubleshooting
Post by: CheapPedalCollector on September 14, 2021, 05:37:33 PM
I was going off his first post where he said something shorted and it worked as intended, so I figured the clock and everything is functioning correctly.

If it's open entirely when testing Q9 between gate and drain and source and drain, probably the issue. It's a FET, usually SKY30A.
Title: Re: Boss CE-2 troubleshooting
Post by: Kevin Mitchell on September 15, 2021, 08:00:36 AM
I was going off his first post where he said something shorted and it worked as intended, so I figured the clock and everything is functioning correctly.
Oops! Missed that  :o

Carry on  :icon_lol:
Title: Re: Boss CE-2 troubleshooting
Post by: znanjeiimanje on September 15, 2021, 08:07:12 AM
I was going off his first post where he said something shorted and it worked as intended, so I figured the clock and everything is functioning correctly.

If it's open entirely when testing Q9 between gate and drain and source and drain, probably the issue. It's a FET, usually SKY30A.

I just went around every electronic store near me and no one stocks 2SK30A. I also googled equivalents which turned out to be 2N5457 and NTE 458 but no one seems to stock those either.

Any idea what I could put instead of the original transistor in Q9?
Title: Re: Boss CE-2 troubleshooting
Post by: antonis on September 15, 2021, 10:11:26 AM
2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..
Title: Re: Boss CE-2 troubleshooting
Post by: duck_arse on September 15, 2021, 11:03:42 AM
2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..

CHECK  YOUR  PINOUTS whatever part you get.
Title: Re: Boss CE-2 troubleshooting
Post by: antonis on September 15, 2021, 11:22:50 AM
2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..
CHECK  YOUR  PINOUTS whatever part you get.

ARE YOU TALKING (YELLING) TO ME..??  :icon_mrgreen:
Title: Re: Boss CE-2 troubleshooting
Post by: Govmnt_Lacky on September 15, 2021, 11:27:49 AM
I just went around every electronic store near me and no one stocks 2SK30A. I also googled equivalents which turned out to be 2N5457 and NTE 458 but no one seems to stock those either.

Any idea what I could put instead of the original transistor in Q9?

Did you check to see if you had a wet signal before Q9? Like at R22? Also, did you check to see if the wet signal is gone at Pin 2 of IC1? Answering this info would be helpful  ;D
Title: Re: Boss CE-2 troubleshooting
Post by: duck_arse on September 15, 2021, 11:34:20 AM
2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..
CHECK  YOUR  PINOUTS whatever part you get.

ARE YOU TALKING (YELLING) TO ME..??  :icon_mrgreen:

if you have all those parts on your bench, I am emphasising, yes, not yelling.
Title: Re: Boss CE-2 troubleshooting
Post by: znanjeiimanje on September 16, 2021, 03:56:44 PM
Thank you all for the help. The events meanwhile unfolded as follows:

2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..

CHECK  YOUR  PINOUTS whatever part you get.

Got a hold of BF256B, put it in, no difference. Still hear the dry signal and nothing else.

I just went around every electronic store near me and no one stocks 2SK30A. I also googled equivalents which turned out to be 2N5457 and NTE 458 but no one seems to stock those either.

Any idea what I could put instead of the original transistor in Q9?

Did you check to see if you had a wet signal before Q9? Like at R22? Also, did you check to see if the wet signal is gone at Pin 2 of IC1? Answering this info would be helpful  ;D

I made a probe and there is no sound at R22 or at Pin 2 of IC1. Only place on IC1 where I hear a sound (quite distorted) is at Pin 6 of IC1.

After reviewing this thread again;

To rule out Q9 you could just check for the wet signal before it. If it's there but not pin two of IC1 then you'd know that's the problem.

My first impression is either the LFO is locked up or BBD or driver is dead.

Check the LFO;
Turn the rate and depth fully CCW and probe the DC voltage going to pin 7 of the MN3101 and see if it's shifting. May be too fast to notice - in that case check the frequency there to see if there's anything going on.

Check the MN3101;
Use a multimeter to check the frequency on both pins 2 and 4 (I compare these to bike pedals, one goes high as the other goes low - effectively driving the two channels of the BBD)

Check the MN3007;
Make an audio probe and listen for pins 7/8 on the BBD. I'm guessing there's no sign of the guitar signal there. Doesn't mean it's bad though - unless the previous steps check out.

Best to test in that order to rule things out along the way.

I did as stated above.

Point 1: at LFO the voltage isn't shifting at all and is fixed
Point 2: Could be my understanding as I am just starting to deal with pedals, but frequency on pin 1 vs pin 2 is a fixed 77, while vs pin 7 it's 100
Point 3: I hear no sound at all



Any other suggestions would be quite helpful
Title: Re: Boss CE-2 troubleshooting
Post by: Kevin Mitchell on September 17, 2021, 09:18:50 AM
Quote
I made a probe and there is no sound at R22 or at Pin 2 of IC1. Only place on IC1 where I hear a sound (quite distorted) is at Pin 6 of IC1.
With no signal on R22 the wet signal isn't making it to the jfet.

Quote
Point 1: at LFO the voltage isn't shifting at all and is fixed
I should have said depth fully CW - that way you see a noticeable scoop in the voltage. But since you also checked frequency you know something is there. More in Point 2.

Quote
Point 2: Could be my understanding as I am just starting to deal with pedals, but frequency on pin 1 vs pin 2 is a fixed 77, while vs pin 7 it's 100
Put the depth fully CW and monitor the frequency of the LFO (pin 7 of the MN3101) as you increase the rate. Verify that it increases as you turn the rate up. Same thing with pins 2 & 4 which are what drives the MN3007. If you observe identical frequencies on pins 2 & 4 you know the clock is fine.


Quote
Point 3: I hear no sound at all
Prof that the clock isn't driving the BBD or the BBD is dead. Did you try adjusting VR3 as you audio probed the BBD's output? Moving forward; suspect the clock or LFO and check the frequency as you adjust the rate. Instructions in Point 2.
Could have blown something from the shorted connection mentioned in your first post. So it would be best to test these externally. If you have a breadboard I have a very simple circuit I use to quickly verify all of my BBDs & clocks. I'll post it if you think it'll be useful.

The thing is, none of us know exactly what's going on with your CE-2. But the fact that there's no signal coming from the BBD's output is THE place to focus on right now. Soldering and resoldering them is not wise. They should definitely be socketed.
Title: Re: Boss CE-2 troubleshooting
Post by: duck_arse on September 17, 2021, 10:19:54 AM
https://pdf1.alldatasheet.com/datasheet-pdf/view/172151/ONSEMI/BF256A/+05327_VLLS.xKdGKYwEI+/datasheet.pdf

the Onsemi datasheet for pinout [end gate pin]. don't look at the motorola datasheet for that BF256, it has a real mess of a pinout diagram.
Title: Re: Boss CE-2 troubleshooting
Post by: znanjeiimanje on September 18, 2021, 05:02:09 PM


Quote
Point 2: Could be my understanding as I am just starting to deal with pedals, but frequency on pin 1 vs pin 2 is a fixed 77, while vs pin 7 it's 100
Put the depth fully CW and monitor the frequency of the LFO (pin 7 of the MN3101) as you increase the rate. Verify that it increases as you turn the rate up. Same thing with pins 2 & 4 which are what drives the MN3007. If you observe identical frequencies on pins 2 & 4 you know the clock is fine.


Quote
Point 3: I hear no sound at all
Prof that the clock isn't driving the BBD or the BBD is dead. Did you try adjusting VR3 as you audio probed the BBD's output? Moving forward; suspect the clock or LFO and check the frequency as you adjust the rate. Instructions in Point 2.
Could have blown something from the shorted connection mentioned in your first post. So it would be best to test these externally. If you have a breadboard I have a very simple circuit I use to quickly verify all of my BBDs & clocks. I'll post it if you think it'll be useful.

The thing is, none of us know exactly what's going on with your CE-2. But the fact that there's no signal coming from the BBD's output is THE place to focus on right now. Soldering and resoldering them is not wise. They should definitely be socketed.

I have done as instructed and indeed, the frequency is increasing on Pin 7 of MN3101. Also, on MN3101 I have the same frequency on pins 2 and 4 of MN3101.

Would be great if you could share the layout to check the BBD and clocks would be great, so I can make it these days and test this. Thanks a lot for the help!
Title: Re: Boss CE-2 troubleshooting
Post by: Kevin Mitchell on September 20, 2021, 04:07:29 PM
Ahh I found it so I don't have to redraw it.
Here's a more simple schematic but not for audio. It just shows if the BBD has any life in it (able to pass signal). Pin compatible for MN/V3204, MN3206, MN/V3207, BL3208 (8DIP package) & MN3209. The diode at the output is an LED and there's a switch (or just use a jumper) to change the input's state.
(https://i.postimg.cc/7fWSP0Hs/bbd-tester-mn320-X.png) (https://postimg.cc/7fWSP0Hs)
This was for testing a MN3102 & MN3207. So just swap the power pins for the BBD (clock in pin to pin compatible) and it'll work. I'll update this post tonight to verify as it's been a while since I had used it on those devices.
Title: Re: Boss CE-2 troubleshooting
Post by: znanjeiimanje on October 07, 2021, 10:17:17 PM
Ahh I found it so I don't have to redraw it.
Here's a more simple schematic but not for audio. It just shows if the BBD has any life in it (able to pass signal). Pin compatible for MN/V3204, MN3206, MN/V3207, BL3208 (8DIP package) & MN3209. The diode at the output is an LED and there's a switch (or just use a jumper) to change the input's state.
(https://i.postimg.cc/7fWSP0Hs/bbd-tester-mn320-X.png) (https://postimg.cc/7fWSP0Hs)
This was for testing a MN3102 & MN3207. So just swap the power pins for the BBD (clock in pin to pin compatible) and it'll work. I'll update this post tonight to verify as it's been a while since I had used it on those devices.

Thank you very much for the help. I have finally gotten a hold of a breadboard and hooked it up. Would it be too much to ask how to proceed with the check? Do you have any values I could have at particular points?
Title: Re: Boss CE-2 troubleshooting
Post by: znanjeiimanje on November 13, 2021, 10:57:49 AM
An update:

Unfortunately I couldn't get the BBD circuit above to work (better say I couldn't figure out how to test it exactly), but meanwhile got a hold of another working CE2. Swapped MN3007 and nothing. After that swapped MN3101 and it worked. The chorus does sound a bit weaker than the working CE2, but I guess this is due to the bias which I will have to do once I get a hold of a MN3101.