help me with my lab?

[lkarty]

Hi -

I just finished wiring my soundlab - but it's not working.

I don't know if it's a grounding issue, but I can faintly hear it. I checked the wiring over several times and there doesn't appear to be any problems.

Also - it continuously oscillates.

I don't know what to do - any ideas? This is my first larger project. I'm having trouble with the troubleshooting

Any ideas/hints would be great!

thanks

[Macaba]

Did you use the PCB version?

Things to check-

Solder shorts
Shorts between tracks as a result of incomplete etching
Broken track as a result of etching working TOO well
Component put in the wrong way round
Fried op-amps
Wrong value components (too high resistors?)
Power supply voltages are correct
Power is getting to all parts of circuit.

Just a few things.

[Clack]

what are you listening to it with?
what do you mean by oscilation like a slow pulse or a tone?

have you tried replacing any of the the IC's? were the amp is?

you could check the jack see how its wired? ( I always do stupid things like solder it to the switching part or earth )

sorry its easier to pick at the simple things first

you could have some dud soldering id check things with a multimeter

[lkarty]

thanks guys -

maybe it's a fried op-amp.

I seem to be getting voltage throughout - but i'm not sure what voltage i should be getting?

I really don't see any shorts or ??

It's most definitely pulsing...

[Pehr]

I had the same problem, but it was just the low-pass filter that was turned all the way down

[Uncle Krunkus]

Yeah,
definately check every setting as there are a number of ways you can get the SL to output nothing.
Also check the wiring of pots, especially the mixer section.
Don't overlook the possibility that you mis-read a resistor code. I still do it from time to time!
Good luck.
P.S. if you don't find it in the next couple of hours of investigating, re-post, have a break, and we'll get out the big guns!

[lkarty]

Thanks for the help!

Well - I checked the individual modules and I seem to be getting signals from them.

When I checked IC3 I wasn't getting a signal. (used an amp as a signal tracer)

I'm going to check the resistor codes tonight! I'll let you know what happened.

[Clack]

some signals could be too slow to be audible, did you use a pcb ordered from the site?

[Wild Zebra]

Did you socket your IC's?

IC3 is the VCA

So if your not getting anything from it try and swap it out.

I've had bad IC's before

[lkarty]

yes, i used the pcb from the site. I swaped IC3 - no luck. geez! what have i done wrong?

It's strange, all I hear is the LFO and oscillator2. I get a signal from OSC1 and Noise when I use a signal tester, but I dont hear them when I plug in the output jack - ??

[v-un-v]

[v-un-v]

[Uncle Krunkus]

Check whether the signal tester shows Osc1 going into the mixer pot (for Osc1) if it does, check what's coming out (ie from the wiper of that pot) a faulty pot can literally disconnect the wipers from the track inside.

[Danno Gee Ray]

I would also recommend you verify the ground connection of r-27. I just finished building my soundlab last night (pictures soon), and had a very similar experience to yours. My symptoms were a pseudo random oscillation / bleed through of LFO signal (free running) as well as a reversal of the main output potentiometer operation. That is to say when I turned down the output it went UP! This afternoon I looked at that part of the circuit and discovered that I had overlooked this connection. R-27 was "floating", as well as all the rest of the front panel pots and switches wired to it. I think I inadvertently discovered a new "chaos" mod for the thing (lol).

Hope this helps.
Danno