My first guess is that something is wrong with LFO #2 and the output
is stuck near the positive rail. Have a look at U5 pin 14 to see if
LFO #2 is oscillating. If that looks good then trace the LFO signal
through U7B and then into the driver for D3 (U4B, VR4, Q9, and Q6).
That's where I'd start looking.
>I just finished building my first kit, a '410, and it sounds great...
>mostly. Sadly the third filter doesn't seem want to play ball.
>
>It passes audio, but it's stuck at the highest setting, up around 30k,
>rendering it useless. No cv or knob twiddling makes it budge.
>
>Also - and maybe this is related - the second LFO doesn't produce an
>effect on the second or third filter. So basically the LFO switch does
>nothing. The first LFO works fine.
>
>I pulled the '410 out of the rack and detached the pcb from the bracket
>(sigh) to have a good look, but the soldering looks fine. There don't
>appear to be any shorts, unless they are a case of solder from the via
>holes (which are all filled) touching the underneath one of the mounted
>items, if that's even a concern. Also, I checked the resistors in the
>"filter 3 section" of the pcb (so R8, R10, R42, R58, R59) and
>everything is in the right spot.
>
>Given that this is the first time I've done soldering work of this
>scale since high school, I'm sure it's something I've done wrong, for
>example that one of the connections isn't soldered well enough, but I'm
>hesitant to just pull everything off the pcb and start again. Do these
>problems sound like they can be traced back to specific
>resistors/capacitors/etc?
>
>If anyone has any suggestions they would get my infinite gratitude. I'm
>really happy with the sound of the unit thus far, now if I can just get
>it 100%...