Vintage Electro Harmonix Bad Stone Problem

[GuitarFreak302]

Hello,

I have a vintage Electro Harmonix Bad Stone and it is producing a high pitch whine. When the pedal is bypassed it produces the clean guitar sound but as soon as it is engaged, it gives off the high pitch whine. The pot and selector switch positions do not make a difference, there is always a high pitched whine. I have replaced the electrolytic caps, the lm324n for the LFO and the CD4009 and it did not change anything. Below is the schematic.






Here are some voltages I measured:

IC A:

1)       4.169

2)       4.222

3)       4.142

4)       0.00

5)       4.153

6)       4.197

7)       4.275

8.       7.76



IC B:

1)       4.124

2)       4.120

3)       4.026

4)       0.00

5)       4.110

6)       4.181

7)       4.179

8.       7.76





IC C:

1)       4.179

2)       4.179

3)       4.174

4)       0.00

5)       4.156

6)       4.196

7)       4.239

8.       7.75





IC D:     

1)       4.171

2)       4.172

3)       4.161

4)       0.00

5)       4.190

6)       4.181

7)       4.133

8.       7.74





IC F:

1)       3.549

2)       4.136

3)       4.135

4)       7.74

5)       4.107

6)       4.072

7)       4.113

8.       4.073

9)       4.135

10)   4.125

11)   0.00

12)   4.826

13)   3.921

14)   6.472





2n5088:

               

                E: 4.064

                B: 4.657

                C: 4.066





Thanks,

Ryan

[GuitarFreak302]

Here is a better schematic:

[thermionix]

SMPS?

[GuitarFreak302]

I am using a 9 volt battery

[thermionix]

Does the noise level change at all if you move it around or to another room?  Just wondering if it's picking up EMI.  If not, I guess audio probe.

[Scruffie]

I've had this problem once or twice before with vintage EHX pedals and it was a bad op amp oscillating so audio probing is definitely the route to go.

[GuitarFreak302]

Thanks for the help. It ended up being an opamp.