SL Ultimate LFO question

Carlosjr · Joined: Nov 09, 2009 Posts: 2 Location: Finland

Hello!
I was just wondering about the LFO:s LED, should it blink or be always on? I'm having some trouble because the LFO:s don't work. On my SLU the LED:s are currently always on. I looked at the schematic an it seems to me the LED:s should follow the oscillation? Any suggestions on what might be wrong?

-Sampsa

Antimon · Posted: Mon Nov 09, 2009 4:18 am Post subject:

Carlosjr

The leds blink in time with the LFO oscillation on my Ultimate. You say that LFOs don't work? I think the leds are linked pretty close to the actual LFO CV, so my guess is if you get the LFOs working the leds will start blinking also.

I've had some problems with LFOs stopping, and the problem has nearly always been that the circuit is open somewhere, i.e. a wire has come loose or I forgot to put solder it in the first place. Check the wires on the frequency knobs R253/R265 first - are they all in place?

The Ultimate has a pretty good layout on the PCB (compared to the minisynth at least). I'd go over the wires from the PCB to the panel one more time, though you've perhaps done that already.

Also, check Ray Wilson's description of the signals (http://musicfromouterspace.com/analogsynth/SOUNDLAB_ULTIMATE/page2.html#SCHEMPAGE11) and check the control voltages on the spots he mentions in the text. A scope is invaluable when doing this kind of troubleshooting.

If both LFOs are non-working, there may be something you've misread in the specs. Doing a meticulous comparison between wires and the diagrams (with the help of a meter or a scope) can reveal this. It may seem like a dull kind of work but usually it pays off.

/Stefan

Carlosjr · Joined: Nov 09, 2009 Posts: 2 Location: Finland

Thanks Stefan!
I did some troubleshooting and after a while I finally found the problem. I had replaced resistors 250 and 262 with 270 Ohm instead of the 270k resistors.

Embarassed

It turned out that the LFO:s where oscillating but extremely slow.

-Sampsa

Antimon · Posted: Wed Nov 11, 2009 6:58 am Post subject:

Glad you found the problem. thumleft

That's happened to me as well.

/Stefan

eXisteNz · Joined: Jun 08, 2010 Posts: 48 Location: Italy

HI i have a problem on the lfo 1 the led is blinking and the speed is in relation with the lfo frequency, but theres non affct on the vcf an no signal on the front panel connections.

Doesn't flow voltage on the x94 so on s5 on the pin connected to x94, but on r 246 and on the others pins of s5 theres an oscillation, the transistor works fine too.....i changed r245 3.3k but still no voltage at his pins....
Can anyone help me please?
I'm lot frustrated and i'm going to build another separate lfo....