Tonepad CE-2 debug

[Fp-www.Tonepad.com]

 

[Auke Haarsma]

nice!

Did you solve the 'distortion' too?

[John Lyons]

Yes, somehow the distortion cleared up as well...!

By the way. Thanks Andre. Pretty much started the clean up which led to the resordering everything which brought it back to life.
Lesson: When it doubt resolder everything. Should have known that.

John

[wui223]

Sorry for hijacking and reviving this old thread. I am debugging a BOSS CE-3.

Problem is: no chorus effect,only clean sound from output. I read up the threads about CE-2 for some ideas to repair mine.

For CE-3 the BBD driver is MN3102 and BBD is MN3207, the LFO is working fine as i got fluctuation voltage on the output of IC5(LFO chip).

But i found out voltage reading at MN3102 pin 8(Vgg out) is 6.65v but the pin 4(Vgg) of MN3207 is mere 0.30v. BTW these 2 pins are connected directly. Anyone got any idea?

Thanks.

[Andre]

I think it's crucial to find out why you measure different voltages at pin 4 of IC3 and pin 8 of IC4.
What happens if you just short those pins?
Furthermore the Vgg of 6.65 Volt is quite low.
Since Vgg is 14/15 Vdd, Vdd should be 7.125V in this case.
What is the voltage at pin 1 (Vdd) of IC4 ?

André

[wui223]

pin 1 at IC4 is 7.18v but my battery is 8.88 when measured. The different voltages at pin 4 of IC3 and pin 8 of IC4 is now solved, it happened that leg 8 of IC4 is not connected to PCB due to broken pin. But now the voltage at pin 4 IC3 still not same with pin 8 IC4 but closer.

[Andre]

But now the voltage at pin 4 IC3 still not same with pin 8 IC4 but closer.

Given the fact that the distance between those pins is really short, you should really get the same values on both pins (within 0.1 V).
Other then that, I think the voltage at pin 1 of IC4 should be approx. 0.6 V less the the battery voltage, and not 1.7 Volts.

Could you measure the voltages at the pins of transistor Q7?
Maybe you can "audioprobe" the circuit and check where the audio stops.

André

[wui223]

I check the Q7, the emitter voltage is 7.00v while my battery 8.24v

I check pin 8 of IR9022 gives 7v also while from the schematic i got from this forum, it should share the same voltage supply as the other opamps (IC1 , IC2). This pedal is original so i wonder what is wrong here. Anybody ?

[Andre]

The schematic is wrong.
If you check the layout you will see that pin 8 IC5 is also connected to the emitter of Q7, so this means that the LFO, BBD and BBD clock are all fed by Q7.
Maybe this is done to prevent LFO ticking.

André

[wui223]

I read up the MN3007 datasheet, the V_DD is suggested -15v. But i measure my CE-2 got something like +7~8v.

Can anyone explain ?

[Andre]

By reverse wiring the power pins Vdd & Gnd of both the BBD and BBD clock, you avoid the need of a negative powersupply with positive ground.
If you check the Supply Voltage Characteristics in the 3007 datasheet you will see that it will work from -5 V up to -16 V.
However signal to noise ratio will be worse and THD will be little more at lower supply voltages.

André

[wui223]

Surprisingly, from the schematic i got now. CE-2 is wired like Andre said.
But CE-3 is different story, the Vdd connected to Q7 while ground is ground, mean positive supply neg ground.

Is it the mistake in schematic ?

[Andre]

No, I think you overlooked the fact that CE-2 uses MN3007 (negative power) and the CE-3 uses MN3207 (positive power)

André

[wui223]

Yes just found out the fact. So i come to a dead end now, what to check next if the voltage on all IC is correct ?

CE-3 i can get clean signal in bypass and effect mode, but CE-2 i get no signal at all so i guess the FET switching might be faulty. Do i need to replace all FETs in the bypass circuit?

[wui223]

I use audio probe to check my CE-3. Below is result:

pin 1,7 of IC1 pin 1 of IC2 got audible signal.
pin 3 of MN3207 got audible signal.
pin 7,8 of MN3207 and pin 7 of IC2 no audible signal.
IC5 give ticking sound (LFO ticking?)

My questions:
1. pin 7,8 of MN3207 is output so i guess i should expect audible signal?
2. pin 7 of IC2 no audible signal means bad IC ?or is it related to question 1?

Thanks for any input.

[Andre]

I suggest you use an audioprobe to find out where the audiosignal stops.

but CE-2 i get no signal at all so i guess the FET switching might be faulty. Do i need to replace all FETs in the bypass circuit?

In the CE-2 schematic I have there is only 1 FET which switches the effect signal to the output.
The dry signal is not switched, but has to pass Q1 and both opamps of IC1.

So I think it's not the bypass circuit, but maybe some power problem.
Have you checked the CE-2 voltages against my CE-2 voltages posted earlier in this thread.
My CE-2 is a Tonepad build, but I don't think that'll make a difference.

As far as your CE-3 concerns, I'm out of ideas. I'd love to have this thing on my desk and help you out, but I think distance will be a problem.

André

[Andre]

Your post crossed mine, so forget about the first line

[Andre]

My questions:
1. pin 7,8 of MN3207 is output so i guess i should expect audible signal?
2. pin 7 of IC2 no audible signal means bad IC ?or is it related to question 1?

1. Yes
2. Not necessary.

There can be 2 other reasons:

1. Misbiasing of the input (Have you tried rotating VR-3 ?)
2. Absence of BBD clock

I can't think of an easy way to check the BBD clock without an oscilloscope however.
Anyone ?

André

[wui223]

Yes, i rotate VR3 to set bias but no chorus sound all the way from min to max setting.
Where can i find info about the BBD clock? is it the MN3102 u talking about ?

[wui223]

Finally got the CE-2 chorusing. But still one problem to be solved. The effect once switch on, the chorus effect is there in both bypass and effect mode. I guess the flip-flop circuit is faulty, anyone?

PS: i found my mind split to two since working on both CE-2 and CE-3 at the same time