Small Clone Not Chorusing

Started by propska, June 19, 2005, 04:24:17 AM

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propska

Turing posted the same problem, but I didn't want to hijack his thread.  

The small clone I built passes the uneffected signal, but not the modulated signal.  I've replaced all the ICs, transistors, double checked diode orientation, and measured the resistors and caps (at least the ones in the my DMM range (about .01-30 uF).  I also have played around with the trim pot too.  I used an audio probe and I get signal all the way up to the 12K before pin 1 on the BBD, after that I get nothing.  I do get signal on pin 3 after the 33K.  

The mods I have are a Vibrato/Chorus switch and a DPDT Depth switch (toggles between 150 pf and a 180 pf).  There is no LED and the power is from a 9V wall wart.  

The voltages off the chips and transistors are as follows:

LM358
1- 2.65 V
2- 2.62 V
3- 3.55 V
4- 0 V
5- 2.44 V
6- 1.97 V
7- 2.74 V
8- 8.44 V

CD4047
7.26 V off 4,5,6,14
0 V off the rest

MN3007
1- 7.26 V
2- 0 V
3- 6.94 V
4- 0 V
5- 0 V
6- 0 V
7- 5.40 V
8- 5.40 V

4558
1- 4.22 V
2- 4.23 V
3- 3.38 V
4- 0 V
5- 4.11 V
6- 4.22 V
7- 4.21 V
8- 8.43 V

Q1
B- 7.22 V
E- 6.82 V
C- 0 V

Q2
B- 4.88 V
E- 4.73 V
C- 8.42 V

Q3
B- 7.89 V
E- 7.25 V
C- 8.42 V

Any ideas?  I've been trying to trouble shoot the past couple weeks, but haven't been able to figure it out.  I may just end up re-etching the board, starting over, and checking each component as I repopulate.

KORGULL

Your Q1 looks off, check everything out around it. Did you use a 2n5087 PNP?
Some of the MN3007 and CD4047 pin voltages aren't so good either, but the transistor problem might be what's throwing those out of whack.
Did you use sockets for the ICs? If not maybe you damaged the MN3007?
Good luck.

propska

i socketed all the transistors and ICs.  i did use a PNP.  I'll try switching it out.  I don't think I fried the BBD because I tried two and neither worked.  That and the BBD leads never touched the solder tip.  

Thanks

propska

KORGULL-

Turns out it was the Q1.  I replaced it and it works well now.  Thanks again.

Fp-www.Tonepad.com

Just for the record.

My voltages at the MN3007 (B+9.6V):

1. 8.93V
2. 4.45V
3. 5.54V
4. 0.00V
5. 0.00V
6. 4.44V
7. 5.33V
8. 5.33V

Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com

propska

Thanks again.  I'm using the chorus in my pt80 effects loop and it's exactly what I was hoping for-very warble-like on the more subtle settings.    

Now I'v got an extra MN3007.  Any suggestions on a pedal to build with it?  I was thinking of building another small clone to put in the effects chain.

Fp-www.Tonepad.com

Great!

Check the Ibanez 301 Flanger at www.tonepad.com I like it very much.

Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com