weird soundlab problems

thapoke · Posted: Mon May 22, 2006 2:17 pm Post subject: weird soundlab problems

Arg!

My soundlab worked fine for a little while , but now has started to do lots of weird things.

When i power it up i can hear the oscillators going up and up in pitch till they go to high to hear. then i can still put the filter into self oscillation but eventually after a minute or so the frequency of that will drop and then the whole thing will just stop making any noise. i've built it patchable and have checked each section individual but there just seems to be nothing doing after it cuts out like this.

I'm imagining it is something to do with capacitors as it takes a while for the pitch to rise up, but i have no idea.. the batteries are still fresh though and i tried changing the lm13700's and osc ic's as well but the same problem happens...

any suggestions?

neo644 · Joined: Aug 18, 2005 Posts: 43 Location: Argentina

did you check the batteries voltage? it may be that they are running low.
have you used any replacement ic's and/or leds indicators? cause that makes your soundlab eat more current making your batteries die faster.

thapoke · Posted: Tue May 23, 2006 12:33 am Post subject:

nah , batteries are fresh , and no led's

Uncle Krunkus · Posted: Tue May 23, 2006 7:13 am Post subject:

My gut feeling is a faulty pot. Not sure why. Partly 'cos it used to be fine. Partly 'cos a faulty wiper would mean that a CV would 'float'. A lot of pots are dodgy even when brand new. Easy to check anyway.

Mr Swirling Vortex Man · Joined: Jun 13, 2006 Posts: 23 Location: Australia

Hi -- Just wondering -- any luck with a fix for this issue as I am experiencing the exact same problem. Newly completed -stock standard Soundlab that was working well for a while. Now when I switch on, VCO 1 starts off sort of in tune and then gradually rises to the bats and dogs freq range after being left on for a while. Fortunately VCO2 is still OK.
Regards,
Adam

Uncle Krunkus · Posted: Wed Jun 14, 2006 4:55 am Post subject:

Did you use LF44Xs or did you substitute TL07Xs?
The reason I'm asking is that mine is fine, I used the LFs, and substituting TLs is the most obvious difference there could be between them. Ray said that TLs should be alright but that he vaguely remembered some problem with them.
Anyway, let me know what substitutions you did, if any, and we'll go from there.

Mr Swirling Vortex Man · Joined: Jun 13, 2006 Posts: 23 Location: Australia

Hi Uncle K,

I used LF444s. Last night I was experimenting with part substitutions. One thing I did was replace VCO1's LF444 with a TL074 (because the rising pitch problem was occuring in VCO 1 only). Lo and behold -- VCO2 started to exhibit the same rising pitch problem even though I had not touched its components. Hmmm... the TL074 uses more power... right? I put the LF444 back into the VCO 1 socket and VCO 2 was then stable again. I checked my battery voltages which I previously had thought to be OK. (I opened a fresh pack a couple of weeks ago). Interestingly one battery was now showing 8v on the meter and the other only 6v. I've just got some new batteries which I'll test once I get home. However, I suspect that I may have fried a capacitor or 2 in VCO 1 while I was experimenting, so I may need to get some more caps as well before I know whether the problem is solved. I'll post again once I've got these issues sorted out and tested.

Possible morals of the story:
1)Do not underestimate the problems power supplies can produce.
2)Always check and recheck the bloomin' obvious!
3)"New" batteries are not always fresh batteries.
4)Batteries may/will discharge at different rates for a variety of reasons. (ie: I got 6 and 8 volt readings off batteries that had been in use for the same amount of time).

Happy/infuriating trouble shooting to all!

Mr Swirling Vortex Man · Joined: Jun 13, 2006 Posts: 23 Location: Australia

Yoinks!
Sorry for wasting your time folks -- It really was just the batteries. Its now oscillating away happily and stable. Fortunately, I hadn't fried any components. Strange though, that everything else was working correctly except for VCO1. The good thing is that I learnt a lot in the process.
So beware ye! Of batteries that fail in the night!

On the even more upside -- I finished adding an external signal input to my 'lab last night. Now I can process external sounds through its filter and VCA. I also got around to adding my CV and gate sockets.

mosc · Posted: Fri Jun 16, 2006 1:10 pm Post subject:

Wild Zebra · Posted: Sat Jun 17, 2006 8:18 am Post subject:

Good to hear it's working. I was buying those "dollar store" batteries for a while and I was having problems. Then I bought them there "copper tops" they've been in my SL for almost a year and running strong. I feel blessed I got my SL working being a electronic novice. I had a few friends try and commission me to make them one, but I dread it not working and have to break the bad news of several hours of debugging after so much time and money went into it, but I guess thats the spirit of learning and DIY.

Have fun take care

Mosc I been having alot of fun with my Cracklebox I'll have to post pics soon, I look forward to the batteries running out. Who's need a magazine in the toilet when you have a cracklebox. hahahaha

dnny · Posted: Sat Jun 17, 2006 2:22 pm Post subject:

mosc · Posted: Sat Jun 17, 2006 2:37 pm Post subject:

I've never heard of toilet keyboards. Very Happy

Certainly a great idea. Idea

Wild Zebra · Posted: Sun Jun 18, 2006 11:55 am Post subject:

Dnny, I thing we're onto to something. Analog crappers, midi toilet seats, CV plungers!

dnny · Posted: Sun Jun 18, 2006 12:52 pm Post subject: