pitch Witch

[karelle]

Hi,
this is my first post and my third build so pretty noob.

I finished the Pitch Witch and it almost work, but there is no modulation in the pitch... I have bypass and FX Delay working but no pitching.

It looks like the yellow LED tension is not modulated by the JRC4558 (I used RC4558D Instead)

I don't really know how to troubleshoot this, but I tried genuinely (desperately) to put a Rainbow led in parallel of the Yellow Led, and there was modulation. But not correlated to the 3 potentiometers (Speed Wave Depth) so i guess it happened just because of the Rainbow Led.

I measured the output of the RC4558, 10,5 Volts constant.

I don't have anything to send a picture, but maybe a hint to understand how the things should be working ?

EDIT

At the first try, nothing was working because i used a weird 4pole footswitch and the wiring wasn't correct. Now the wiring is ok but Maybe, because of that, a bad routed 9v tension damaged the IC's ? How do you check them ?

P.S I'm not in the good section, sorry, should by in troubleshooting...

Thanks, Bests.

 

[karelle]

I investigate with a continuity test, and I have more precise questions :

- How does the VREF works in the schematics ? Where does it come from ? Should it be the same electric point such as the ground ?

Because in my build, on the RC4558 the input 3 and 6 are supposed to be VREF, i guess it's 9 volts but i'm not shure ?

What I measure on those two is
3 : 0V and
6 :7,86V

It might be why the VCO is not working ??

The continuity test reveals that : input 3 and 7 are connected. Which doesn't make sense to me...

Anyone as a lead ?
Thanks

 

[Robert]

VREF should be around 4.5VDC. It comes from the voltage divider R10 / R11, that's a good place to start.

R10 should have 9V on one side, 4.5V on the other.
R11 should have 4.5V on one side, 0V (GND) on the other.

If these measurements match yours, you need to check continuity between the R10/R11 junction and Pin 3 / Pin 6 of the RC4558.

 

[karelle]

thanks !

Nothings seemed to be working correctly in this area :
I had 8.8v at both sides of R10
0v at both sides of R11

R11 was well connected to the ground and Pin 3/6
R10 was well connected to the Pin 8 of the RC4558 and the pin 3 of L78L05 but not to R11

I soldered a wire between R11 and R10, and yeah ! The led intensity is modulated !

I can't see where the pcb is damaged but now it seems to work,

i am going to listen to it now : )

 

[Robert]

I had 8.8v at both sides of R10
0v at both sides of R11

Yep, definitely sounds like an open connection between R10 / R11.

Glad you found it!