Boss CE-1 Distortion on wet signal

[Luqqas]

Hello everybody

I need some help. My CE-1 started to distort on wet signal. On dry ("Normal") signal passes fine. On wet ("Effect") it distorts.

Doing some audio probe I found that at MN3002 input (pin 3) signal is ok. On pin 13 & 14 it came out whit the effect but distorted. Not distortion per se, but overdrived, with strong clippling.

This is the schem of my unit:



Also found that at IC3 output signal is strongly distorted, in a square wave fuzz type. Don't know if this noise gate part of the circuit it's supposed to work like that.

Any comments are welcome. Need to fix this vintage beauty.
Cheers!
Luqqas.

[Scruffie]

The BBD bias is fixed in this circuit, the resistors could have drifted causing the BBD to be mis-biased which would cause clipping or one of the electrolytics in the biasing circuitry could have started to go bad and is affecting something in that area.

It's also possible the clock circuitry is not providing a clean square wave any more.

Take voltages of the BBD & Q3-6.

[Luqqas]

Thanks Scruffie.

Voltage readings:
MN3002
1    4.66V
2    -7.16V
3    -.353V
4    -13.39V
5    0V
6    0V
7    0V
8    0V
9    0V
10  0V
11  -11.43V
12  -6.86V
13  -1.5V
14  -1.5V

Q3 
E    0V
B    -340mV oscillating
C   -7.2V

Q4
E    0V
B    -400mV oscillating
C    -6.8V

Q5
E    -14V
B    -14.9V
C    -8V oscillating

Q6
E    -14V
B    -15.2V
C    -5.9V oscillating

Hope this helps

[PRR]

Replace these caps. If they leak it could cause to wrong BBD bias.

[Luqqas]

Thanks Paul. I'll do that and report.

[Luqqas]

Ok, I make some time and change: C13, C14, C16 (all involved with MN3002).

Also change C22 and C17 (involved with clock part of the circuit).

Still get wet distorted signal on pin 13 & 14 at MN3002 outputs.

This is beginning to worry me 

[chorusjunkie]

As i understand,it only distorts when the chorus effect is on? Can you achieve distortion by cranking the level and the input gain switch to high when its off?

[Scruffie]

Assuming the BBD voltages didn't change with the cap swaps your input bias (pin3) is incredibly low and the Vdd & Vgg voltages are off if i'm remembering the pinout right.

Measure again now the caps are swapped.