1980s Boss CE-1 chorus pedal sounds out of tune, any ideas?

Just bought a Boss CE-1 that goes out of tune whenever the chorus is dialled up, here's a video of the pedal:

https://www.youtube.com/watch?v=KYVR1jdgQVQ

As you can hear the chorus wobbles a lot more out of tune than it should, a working Boss CE-1 or CE-2 (or any good chorus) doesn't do this.

A working Boss CE-1:

https://www.youtube.com/watch?v=VnW-FJsalTA

Any idea what's wrong and if it's easy to fix/adjust without replacing parts? 

Thanks in advance for your help.

ps: I'm based in East London, UK.

The way a chorus/ADT (automatic double tracker) works is by shifting the pitch both up and down.

They both are shifting the pitch but one is shifting it more and a little faster.

So yes, you can tweak the design to make it slower and less deep.

May be a good learning experience about how effects work..

JR

I understand how choruses work, but this Boss CE-1 does not sound like other CE-1 as it goes more out of tune and is unusable for standard chorus work.

Do you think there is something wrong or can this pitchiness be adjusted inside? 

Thanks.

ps:  Please bear in mind I'm not that knowledgable technically about pedals...

Farringdon said:

I understand how choruses work, but this Boss CE-1 does not sound like other CE-1 as it goes more out of tune and is usable for standard chorus work.

Do you think there is something wrong or can this pitchiness be adjusted? 

Thanks.

ps:  Please bear in mind I'm not that knowledgable technically about pedals...

Click to expand...

I don't know how much cheap pedals vary from unit to unit.

The pitch shift is created by modulating the clock controlling a delay line.  If the signal gets clocked out faster than it was clocked in the waveform is squeezed tighter (shift higher), when it gets clocked out slower the waveform is stretched out (shifted lower).

You need to inspect the schematic... probably a triangle wave controlling the voltage to period (or voltage to frequency) convertor controlling the clock.

I am not familiar with the design so I can't opine whether its an adjustment, faulty part, or marginal design. Like I said a learning opportunity for you.

If this is too complicated you can try hitting it with a hammer, but odds are that won't work (I'm kidding about the hammer).

JR

Look at the oscillator, ideally with a scope, if you can get a working unit and compare them even better.
There is the scheme and some waveforms you could check


If I had to start shooting in the dark I'd go looking for some loose contacts, resistors switch or pot associated with the chorus intensity control, continuity test and checking the resistors with a DMM would be enough instrumentation to start with that.

Also you could check J for example with chorus at minimum and expect about 4VAC with a DMM. Ideally I'd check K with an scope to see if it's a triangular or goes crazy saturated but JUST with a DMM is hard to look. About 6.5VAC would be fine, much higher than that you have a problem.

JS

Above is a description of how they work. I've owned a couple of CE-1s and they've been pretty subtle except when turned to the max

If you look at the schematic, there is a trimmer VK01 at the output of the MN3002 BBD chip. That's the only trimmer I can see

If you look at the data sheet you'll see the basic idea
http://www.datasheetarchive.com/dlmain/Datasheets-110/DSAP0010394.pdf

I don't have any more info than that

It'd be worth opening it up to see if it's been modified

Good luck - they are amazing pedals!


Nick Froome

The adjustment on the output of the BBD is to trim out clock frequency feed through.  The analog delay only has valid data for one phase of the clock, so a one stage sample and hold repeats the last sample of data so it looks like a continuous stream of data. Since the mosfet followers have different Vp the trim is to reduce a DC error at the clock frequency between the samples.

JR

Thanks for the info, I'll see if I can play with the trimmer.  Anything else is I should probably hire a tech to do as I don't have the equipment or the skills unfortunately....  if anyone knows a good pedal repairer in London please let me know.

Must say that the CE-1 is not a "cheap" pedal though, I think it's the most expensive chorus pedal one can buy nowadays (around $400-$600 US, depending on condition).

Farringdon said:

Thanks for the info, I'll see if I can play with the trimmer.

Click to expand...

No, don't touch it, it has nothing to do with the pitch shift. It's to reduce HF clock noise .

Anything else is I should probably hire a tech to do as I don't have the equipment or the skills unfortunately....  if anyone knows a good pedal repairer in London please let me know.

Click to expand...

it looks like depth of the effect is variable... does it sound too severe when you adjust it for less depth?

Must say that the CE-1 is not a "cheap" pedal though, I think it's the most expensive chorus pedal one can buy nowadays (around $400-$600 US, depending on condition).

Click to expand...

Sorry, I used to design a rack mount studio delay line/chorus/ flanger (35 years ago).

$400-$600 sounds pretty expensive for a pedal. For that it better sound good.

JR

Yeah it does have a great and unique tone, I've got quite a few choruses on racks and pedals but this is the best sounding one. 

The chorus warbles too much on any setting except zero.  When it's on vibrato mode the pedal works fine with no issues.

When opened up, there seems to be a jumper cable connected from the tip on the left input to the right input.  Is that normal?  Someone might have messed around as the one of the output sockets looks different from the other one.  This is a stereo pedal with mono out and then an extra output for stereo use.  Maybe both outputs are "stereo" at the moment, and for correct stereo usage the pedal is supposed to creat one "effect" only channel and one "direct" channel? 

Farringdon said:

...
The chorus warbles too much on any setting except zero. 
....

Click to expand...

Now I can bet the potentiometer went like a cucullatus... Could be a resistor or a wire but I put my last coins on the pot. If you don't want to change it just bodge a 2k2 resistor between green and orange wires in the intensity pot and check what happens, or easier, short them, move the pot around and tell us.

JS

If you look at the schematic it seems the the output from Q13 feeds the output jack via the normalling on the stereo output jack, where it mixes with the input signal

So the main output is a mix of original & effect unless you put a jack into the stereo output - which defeats the effect output to the main to make main = direct and stereo = effect

If it's jumpered otherwise I'd revert back to the original setup

Nick Froome

I finally gave the CE-1 to a tech and he reckons the problem is the MD 3002 bucket brigade IC being faulty.  Does this sound right to you guys?

Essentially the problem is - as you can hear in the video - when the chorus is switched on we can only hear the effect signal and not the original signal.  With vibrato switched on everything is fine.

read up on analogue chorus function

vibrato IS more or less the chorus without mix-in of dry signal

It would seem that your 3002 bucket brigade is fine - this is the one responsible for the vibrato part of the chorus.

So error is probably in the "dry" signal path

Jakob E.

gyraf said:

read up on analogue chorus function

vibrato IS more or less the chorus without mix-in of dry signal

Click to expand...

Not sure where you read that...  While yes that is "a" difference it is not "the" difference and the dry path is not the likely suspect for the OP's complaint related to pitch shift (out of tune?). The delay path is responsible for any and all pitch shift so related complaints about pitch shift should focus there. (I'd look at clock frequency controls, LFO?).

While opinions vary, apparently. 

It would seem that your 3002 bucket brigade is fine - this is the one responsible for the vibrato part of the chorus.

So error is probably in the "dry" signal path

Jakob E.

Click to expand...

For TMI I would characterize "vibrato" as relatively quick pitch shift (warble) to a single voice, while "chorus" is an attempt to fool the listener into believing there is more than one person singing, or playing the same part. Chorus or ADT uses a much less severe pitch shift (less deep and slower changing), then adds that altered signal to the dry path to create the apparent double tracking. 

So yes that dry/wet is a mechanical difference but not germane to the perceived fault, that is all in the wet path IMO.

JR

i would start down in the right corner of the schematic. Work your way to the 3002 BBD and check if something is wrong. The switch 4? Maybe only one side works so you get some kind of strange mix of the Vibrato and the chorus funktion?

Or maybe it is a cap that have lost to much of its value due to age and now doesn't work as it should? If that is the case i would do a full recap.

S

Hi,

this is how in/out section looks like in my CE-1.


gtr

The problem wont be at the jacks

Not to contradict myself, but if the problem is "that you don't hear the dry signal in chorus mode", the problem is definitely not the MN3002.

If the problem is the rate or depth of the pitch shift look at the clock control circuitry,

if the problem is no dry signal, investigate the dry path circuitry...

JR