CE-2 "Corrrral Chorus" - Need Help!

[JoeGuitar]

I built a Boss CE-2 "Corrrral Chorus" from the Tonepad site - http://www.tonepad.com/project.asp?id=53

Unfortunately, it does not chorus;  the output sounds exactly the same as the input.  When I put the scope on it, I can see a nice signal going into pin 3 of the MN3007 and a signal coming out on pins 7 & 8.  The signal is still there at the junction of C10, R15 & R16 BUT is gone at R16, C11 & R17.

I was on a roll before I built this one.  I build a Slo clone, a MXR blue box, MXR Phase 90, & a BSIAB and had no problems.  I etch all of my own boards.

Since I obviously screwed something up, I built it on the breadboard (using all new components), but still get the same thing.  So I etched another board & built this one.  I tested every part & triple checked the values.  Still, the same thing.

Any help is greatly appreciated.

Here's a pic of the component side of the board.




Here are the voltages on the transistors & ICs using a Boss PSA adapter for power..

Q1 E 9.63v     B 4.55v      C 4.55v
Q2 E 9.63v     B 5.37v      C 4.86v
Q3 E 9.63      B 5.03v      C 4.65v
Q4 E 9.53v     B 4.45v      C 4.01v
Q5 E 8.29v     B .034v      C 0v

IC1 -4558

Pin 1 - 5.57v
Pin 2 - 5.57v
Pin 3 - 5.56v
Pin 4 - 0v
Pin 5 - 5.57v
Pin 6 - 5.56v
Pin 7 - 5.57v
Pin 8 - 9.63v


IC2 - TL022

Pin 1 - fluctuates from 0.5v to 8.9
Pin 2 - fluctuates from 4.5v to 4.9
Pin 3 - fluctuates from 3v to 6.3v
Pin 4 - 0v
Pin 5 - fluctuates from 4.5v to 4.9
Pin 6 - fluctuates from 1.6v to 6.3v
Pin 7 - fluctuates from 3v to 6v
Pin 8 - 9.63v

Note that on pins 2 & 6 the voltage change is really quick & I don't know if my meter can adjust quick enough to get a "real" voltage on these pins.


IC3 - MN3007

Pin 1 - 9.53v
Pin 2 - 4.66v
Pin 3 - 4.86v
Pin 4 - 8.91v
Pin 5 - 0v
Pin 6 - 4.63v
Pin 7 - 7.65v
Pin 8 - 7.65v


IC4 - MN3101

Pin 1 - 9.53v
Pin 2 - 4.63v
Pin 3 - 0v
Pin 4 - 4.66v
Pin 5 - 0.26v
Pin 6 - not used
Pin 7 - 3.07v
Pin 8 - 8.91v


As seen in the picture below, the sine wave input on pin 3 of the MN3007 is 2.75v




This picture shows the output "wave" on pins 7 & 8 is .25v  The time of the output can be varied greatly by VR1 & VR2.



Joe

[bent]

i got the same problem, and it turn out that it was the tl022 (buy at hongkongsupperseller) that was defect... i put a tl072 in place and the problem was solve...

bent

[JoeGuitar]

Thanks for the reply bent.

I tried a tl072 & there was no difference.     I even tried a NE5532 and still had the same problem.

Joe

[shadowmaster]

Try an LM358 on the oscillator section. I always use this dual opamp for oscillators in choruses, phasers and flangers.

Hope this helps.

Peace.

[Dirk_Hendrik]

Stop looking at that 022! The fact that it fluctuates in this way just tells you your LFO is OK. It is supposed to fluctuate!

Pleas make another scopedump of the BBD output with a wider timebase. Zoomed like this it's impossible to tell if there's different sample levels (and therefore, information) in the signal. Use the same timebase settin you used for the input (full wavecycle) or something.

Are you sure the BBD Bias is set correct?

[JoeGuitar]

Hi Dirk - thanks for your input.

Here's a couple more shots - one full input wave.



And the output using the same timebase.



As for biasing the BBD - no, I'm not sure it is correct as I don't know how to do that....


----------------------------

I noticed that another person had a problem with this build & posted voltages here http://www.diystompboxes.com/smfforum/index.php?topic=56283.0

When I checked the voltages I noticed a huge discrepency on pin 8 of IC 4 (I get 8.91v while he gets 0.58v).  Same thing on Pin 4 of IC3 - these two pins of these ICs are tied together then to C9 & to ground.

Does anyone know what the correct voltage should be here?


Thanks

Joe

[Dirk_Hendrik]

OK,
As it is now there's no information in the output:
case a) Incorrect bias. Keen on coping that output while rotating the bias. When there's drastic changes in that spikey output signal you're good! You should see a sinus sampled in there (you may want to zoom out a little more on your (nice btw) scope.
case b) whatever you bias, nothing happens at the output: Your BBD's input is blown. They are very sensitive to static electricity.

For now, let's focus on A 

[johngreene]

Looks to me like your MN3007 is bad. A couple of the buckets have holes in them.

--john

[puretube]

"VR3" is your bias trimmer...

[JoeGuitar]

Ok, here's a couple of pics of the output of MN3007 with the trimpot at it's min and max settings. 







Is this how it's supposed to look or do I have a bad chip.  Hopefully it's not a bad chip as I have 20 of them & they all behave in the same manner!!!!!!!!!!!

Joe

[puretube]

the "sweet spot" of the trim is somewhere near the middle of VR3 - not at the extremes.
(and turn the timebase a few notches down, when feeding the chip an audiowave)

(sorry, but haven`t seen a bad BBD chip`s behaviour on the scope)

[Dirk_Hendrik]

the "sweet spot" of the trim is somewhere near the middle of VR3 - not at the extremes.
(and turn the timebase a few notches down, when feeding the chip an audiowave)

(sorry, but haven`t seen a bad BBD chip`s behaviour on the scope)

You're right in the looking for the sweet spot.

As for "bad chip's behaviour", it's usually the first input Fet that is defective as result of a static discharge. Result is that no signal will come in and pass to the next stages, resulting in the pictures as seen above.

[JoeGuitar]

Ok - I figured there is no way I have 20 bad MN3007 chips. 

Since the other guy had such a low voltage on Pin 4 of this chip I figured I'd short it to ground & see what happens.

Voila - it works.  Here's what the output of a MN3007 looks like when it's working.



Now, I need to find out why I have such a large voltage here.......  I checked for solder bridges, continuity, etc, etc but it all looks good.   Does anyone know what the C9 cap is supposed to be doing?  I figure if I don't need it, I'll just take it out of the circuit & put a jumper there to ground pins 4 & 8 of the 3007 & 3101.

Joe

[puretube]

looks much better now...

The MN3101 clockchip "generates" a fixed voltage at pin 8, which has to feed pin 4 of the 3007.
This voltage ("V_GG") automatically is supposed to be 14/15th of the supply voltage (i.e.: it generates 14V out of a 15V supply,
or ~ 8.4V out of a 9V supply).
The cap is just a smoothing (reservoir-/lowpass filter-/bypass-) cap.
Don`t ground these pins!

[Dirk_Hendrik]

looks much better now...

Does it?

Or, at the TS, do you have chorus now?
The signal as shown has more resemblance to one of the MN3101 inverter input pins than to the BBD out.

Or:
dammit that the floppy drive of my scope is defective (and the I don't have a correct RS323 cable or a GPIB connection for all that matters  ) or I'd have made some dumps of the correct signal.

[JoeGuitar]

Hi Dirk - Yes it does the chorus thing now perfectly.

If you have a scope, you can find the sweet spot in a sec - just probe the input of the MN3007 - pin 3 - and turn the trimmer till you get as close to a sine wave as you can.

Here's another shot of the output of the MN3007 - you can see all the buckets working if you look close.



Heres the output signal - CP1 - on pin 2 of the MN3101



Heres the output signal - OX3 - on pin 6 of the MN3101 (flip the image over & you have OX2)



An finally, this is my fix until I hear of a better way......



Joe

[puretube]

err, maybe that smiley was the wrong type...

BTW: in the first post, it looks like "E" & "C" voltages of Q1 to Q5 are reversed (?)  

[puretube]

looks much better now...

The MN3101 clockchip "generates" a fixed voltage at pin 8, which has to feed pin 4 of the 3007.
This voltage ("V_GG") automatically is supposed to be 14/15th of the supply voltage (i.e.: it generates 14V out of a 15V supply,
or ~ 8.4V out of a 9V supply).
The cap is just a smoothing (reservoir-/lowpass filter-/bypass-) cap.
Don`t ground these pins!

for a negative supply voltage...

[Fp-www.Tonepad.com]

Those scope pictures are cool, glad to hear you got it working!

[puretube]

looks much better now...

The MN3101 clockchip "generates" a fixed voltage at pin 8, which has to feed pin 4 of the 3007.
This voltage ("V_GG") automatically is supposed to be 14/15th of the supply voltage (i.e.: it generates 14V out of a 15V supply,
or ~ 8.4V out of a 9V supply).
The cap is just a smoothing (reservoir-/lowpass filter-/bypass-) cap.
Don`t ground these pins!

for a negative supply voltage...

i.e.: in this case, where "circuit-ground" represents the "would-be-negative V_DD" for the BBD at pin 5 ,
and the circuit`s Ub= +9V represents the "would-be-ground" for it at pin 1 ,
the V_GG at pin 4 is supposed to be 1/15th less negative than the V_DD, compared
to Ub:  so it should read roughly + 0.6V.

(with a 9V circuit, this means ~ a diode drop  )

AFAIK, the internally generated V_GG : "14/15th" of V_DD of the clock-chip is just a two-resistor
voltage divider, consisting of tightly tolerated  (trimmed) values, e.g.: 1k and 14k...

datasheets:
MN3007
MN3101