Help with Soundlab problems

[nekoneko]

Hello

I built my soundlab a year or two ago, never got it working and left it to finish another day. I've come back to it and can't get it to work, despite rewiring it again.

The problem is the soundlab makes no or little sound. I can only hear OSC 1 which is outputting a continuous high pitched note. The frequency mod does not effect it's pitch. The mixer does not work. I can always hear OSC 1's high pitch even with it's mixer pot turned all the way down.

When the filters all the way down I can hear the LFO (which kind of works, freq knob changes speed and ramp saw switch changes wave) and OSC 2.

When I measure the power rails I get +9v, 0v, and -6v. The batterys are fine I've checked them. I checked the front panel wiring for power, ground etc as I did it and that was fine. I seem to get this drop in voltage when I connected the soundlab to the power rails.

I've checked my wiring 10 times, checked IC's and checked for shorts on the board. I've also read through Rays trouble shooting page and most of this forum.

Please can anybody suggest anything to get the soundlab working. I'm completely lost and would like to move onto finishing the rest of my soundlab. Will be adding Unkle krunkus's stripboard sample and hold + 2 extra VCO's board, guitar trigger, fine tune mod, osc modulation mod, LED's and adding Ray's 10 step sequencer.

Thanks in advance.

[Danno Gee Ray]

Did you use sockets for your chips?

If so, remove the chips and recheck your power rails again.
if they are the same with the chips out, start at the point where power enters the pcb and check component values.

If you didn't use sockets...well, check components anyway.

Try to isolate the power rails in chunks by lifting one end of components etc.

double check diode orientations and Electrolytic cap orientations.

[nekoneko]

Cheers for the advice. I will check tonight. Luckily I did put sockets on for the IC's. Hopefully it will be a small problem.

Wish me luck.

[Danno Gee Ray]

Best of luck.

[nekoneko]

Right heres an update.

I decided to rewire the whole synth because it was a birdsnest and made debugging hard. Plus I used more flexible wire which allows the board to move a bit which is also helpful. It's alot neater now.

After rewiring I tested IC's one at a time and there good. Components check good too. I'm getting + 7.5 0V and -7.5V which is good. Tested batteries and they are putting out about 7-8 V each so they are dying.

So now the soundlab does make sounds! But not the right ones.

With the filter set to 50% I hear the lfo (working great) white noise, OS1. The mixer pots do not change the gain of white noise etc. OS1 frequency pot does nothing, I can just hear constant frequency.

I will get this working even if it's for my own sanity.

Any ideas?

Thanks

[Captain Biscuits]

First thing is "Keep at it" you'll get there in time and it will be worth the effort.

I get the impression that a high proportion of problems are about grounding. It's probably worth making sure that everything which should be grounded is grounded and that everything that isn't isn't.

I finished my Sound Lab Mini a while ago. It behaved really strangely when the batteries started dying and has improved dramatically since I added Ray's Wall Wart 12v power supply. Before I added that the VCOs wouldn't tune very low - once I was giving it the voltage it wanted I got lovely low notes.

Let us know when you crack it.

Good luck & all the best,

Ian

[nekoneko]

Keep at is my moto. Been 2 weeks now.

I had a feeling its a ground thing and removed all ground connections. OSC's went unstable and filter didn't work. LFO frequency knob didn't work properly . Added them and back to same state as last post but mix knob for OSC 1 now works.

I'm using an old metal computer case for my front panel. Plan to add wooden case later. Do I have to ground it?

Can't wait to get the MFOS powersupply board and run it on 12v. Irons out problem of batteries. Also can hook up extra vco's, s&h, guitar trig, led mods and eventually the 10 step sequencer.

This whole debugging phase is helping me to understand how the synth works and how the components effect the circuit.

Nice to have some sound coming out though.

[Danno Gee Ray]

I agree with Ian, Keep at it.

Sometimes it helps to break the problem down into manageable pieces. Take one symptom at a time and work your way through to a solution.

Seems the rewire cured a power supply problem, so well done.

[magman]

Although I've not built a Soundlab, an Ultimate and Expander is on my to-do list, I've got good experience with other synth build projects.

As I'm relatively local to you, if you don't get much headway with your debugging you have an open invitation to come and visit Chez Magman, where with a bit of luck and the liberal application of test equipment we may save the day.

It would be better in the long run for you to get this working yourself (in fact you will learn more because if didn't work first time), but at least you now have a potential fallback position.

Regards

Magman

[nekoneko]

Thanks for the offer magman but I'm too busy at the moment and it would help me a lot to get this working myself.

No real progress at the moment as I've been too busy to carry on debugging and could have probably done with a break. You know can't see the wood for the trees.

The synth will be getting it's case soon and I've been getting more knobs too. It's starting to come together. This thread has helped and stopped me from going mad so I'll keep it updated with news.

Thanks everyone.