Saw animator problems

LektroiD · Posted: Wed Nov 10, 2010 5:03 am Post subject: Saw animator problems

Ok problem 1:

LED 1 stays on solid.. initially I fried one of the 10Ω resistors due to a power rail short in the etching (the + power one sandwiched between the earth rails was short), it's the same side of the circuit where the faulty LED sits...

So far I have replaced the transistor, the 4.7K & 1.5K resistors, the 4148 and also the TL074 at the LED end of the board (there's no component designators listed in any on the layouts so I can't tell you the component numbers of any of these, so I hope my description is clear enough). I have also double checked the board for any more shorts.

I did manage to get the LED to flash (I have no idea how, it just did.. It seems this is intermittent though). The 'off' didn't go completely off, it just dimmed and slowly increased again until it was on solid again.

I have no idea what else to replace to get this to work.

Problem 2:

When I use a saw out of the VCLFO (its the best shaped saw I have - the MFOS ones I own have bad spikes all over the place), the sound seems to lift and drop by a semitone as it goes between the peak and trough of the LFO on the saw animator - like an ambulance 'nee-naw' sound.. When I use the triangle or sine as the input, I get the fat 'supersaw' sound. So it seems to work as a sine animator.

I have done the calibrations with the scope to line up the split in the saw and also the DC offset.

Hopefully I can get this working, as I really like what it does to the sine and triangle waves

yusynth · Joined: Nov 24, 2005 Posts: 1314 Location: France

Concerning problem 1 : can you measure the voltages at pins 4 (+15V),11(-15V), pin 7 (should alternate between +13 and -13V)

For "problem 2"

LektroiD · Posted: Fri Nov 12, 2010 2:38 pm Post subject:

yusynth · Joined: Nov 24, 2005 Posts: 1314 Location: France

If you look at the schematics you will see that the LED has no connection with the MOD IN socket, as such it is intended to be an indicator of the internal LFO rate not from external signal.

Concerning an external CV what do you expect from it, a static CV will have a static effect that is a simple and constant phase shift of the SAW which is not really usefull at audio rate, it may be useful when input a LFO saw.