[sdiy] EFM CVLFO5a trouble

[Dave Magnuson]

At 06:24 PM 5/19/04 +0200, Frédéric Bourgeais wrote:
>
>Hi list,
>
>I'have made the EFM's CVLFO5a, reproduicing PDF schematics on a 
>testboard (note I only made TRI/SQUARE section)
>It is completly mute and don't reply to any CV voltages or Init/rate 
>pots  ..
>
>I checked and recheck, swapped IC but no way..
>
>Anyone can take a look to the shematics, if there is a mistake ? 
>(Swapped -/+ input on TL74, reversed 2N3906 (?)..)
>
>Anyone reproduce this schematics without PCB succesfully ?
>

I'm assuming the PCB layout that you have is identical to the PCB that Tom
sold... if so, there are 2 problems:

1.  Q2 is oriented backwards on screen printing

2.  Q6 is improperly connected to U4.  Cut the trace connecting source of
Q6 to U4 pin 6 and R39.  Reconnect Q6 source to U4 pin 5

Hope this helps,

Dave Magnuson

Resonant Frequency:
resfreq at hoohahrecords.com
http://www.hoohahrecords.com/resfreq/index.html