WSG faint sound

[hewmun]

hello,
i just assembled a WSG.
there was a little bit of trouble at first, but i went back and fixed it, it worked fine. then i decided to hook up the AC adapter. it made a loud hum even in the off position and nothing else, i disconnected it and went back to how it was when it worked with the 9v battery and now it is very quiet.
i checked everything to make sure nothing was out of place or loose or whatnot, and everything seems fine. could i have messed something up when i plugged in the AC?
this is my first project other than the fixing of various instrument cable.
really don't understand schematics or VOM's or polarity or anything like that... seem to learn best with photos.

also i'm having a problem with threading on the parts, the nuts are stripping the threads very easily so i can't clamp them down. the parts move all over the place. especially the output jack.

i took pictures of my box and will post them shortly.

[hewmun]

here it is.
haven't finished the details of the front panel yet, just trying to get this thing to work first.

[valis]

Congratulations on completing the WSG. The WSG was my first PCB project as well. Yours looks cool..

Anyway, it is my understanding that your WSG was working reasonably well and then you plugged it into an AC adapter and it doesn't work so well anymore. Was this AC adapter something Ray recommended? I had never heard of powering a WSG via an AC adapter and it sounds like a pretty bad idea for a novice builder.

Ray has a whole page dedicated to troubleshooting the WSG. Go to the WSG site and click troubleshooting. the silver lining right here is that this is a great chance to do some beginning troubleshooting work which will be invaluable experience for ater.

If the WSG was working well before the adapter incident, I'd try to pop another LM741 in. You should be thanking yourself you used IC sockets. You may want to try replacing all the ICs depending upon what sort of AC adapter you used..

It's always a good idea to double check the orientation of things like electrolytic and tantalum capacitors, diodes and LEDs, ICs, and transistors..

-David

[hewmun]

thanks,
yeah, after a few nudges on the output, it had the nice full sound.

i couldn't really tell which wire went onto which post on the power input, so i tested different combination, probably not a good idea. the hum was the only result on only one combination, the rest did nothing. i based the power input from the matt stanfields wsg blog. i just copied what i've seen in the pictures. just thought it would be an easy addition. guess not. i used a 9v adapter.

other than the quietness, it works fine. still able to get the basic sounds.
i'll try what you recommend to see if that brings the volume back up.
i actually messed up on the LM741 IC socket when i was putting it in. as i was taking it out which wasn't an easy task for me, some of the small PC board rings came out with it. i couldn't put them back it so i just left them out. also one of the bridges on the IC had cracked as i was pulling it out. i don't know if that affects anything. another thing, i messed up on the 470K and put it on the board, after realizing this, i had cut the extra wire off, then i soldered them back on and put it in its right place. it did work with all of this though. so it might just be something the AC did. where can i get a LM741. radioshack?

[Uncle Krunkus]

"Loud hum" sounds like you literally used an AC adaptor, ie; one which puts out 9V AC!
To use a wall wart type PSU, you want an adaptor which has a 9V-DC output, and, you want to make sure you get the polarity right,..... The first time. Putting power into CMOS chips with the polarity wrong will let all the magic smoke escape!!

BTW If you did use an AC output adaptor, then the power would have been reversed for half of the time it was plugged in. That's enough to get the 741 alone too hot to survive!

BTBTW Don't worry too much, we've all done it before! Just replace the chips and see what's what.

[Wizard Mike]

You may want to do something like this to protect your circuit if you're going with a wall wart to WSG. I did the same mod (minus the capacitor) to power my WSG.

http://www.commonsound.com/swash/mNS/wiring.pdf

What your looking for is at the top of the page where the power jack is. You can either bridge the lugs with the LM7809 power regulator or you can install it right on the kludge area of the board.

Here are a couple pics that will hopefully show what I mean.
First is tying in the battery jack with the power jack and the other is the power regulator on the board.

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[hewmun]

ok, i switched out the LM741 along with the IC socket, as i was taking it out the little metal rings on the PC board came off, so it was very hard to solder the new one in place. i made my own rings and put them in.
it works now, though it's a little distorted and quietly hums when i take my hand off the metal plate. and sound cuts out on and off, probably a problem with the output jack.
but the volume is normal, so i can't really complain.
i couldn't find a LM7809, radioshack only had a LM7805, so i'll just stick with battery for now.
thanks for the help.

[valis]

I'm glad you got your WSG running reasonably well. It sounds like you have a grounding issue still. Make sure everything is properly grounded and that you're wiring is correct. I like the WSGs but as a first project, they really run the risk of the wiring turning into a proverbial rats nest if you're not careful..

[reve]

Yeah. I had the same clever idea (run it off a wall wart) and wound up with the same problem -- cooked ICs.

You wouldn't THINK the 9v setting of this universal wall wart would output 15v....

I figured it was just the Logic IC that was cooked, replaced that, and got the faint sound mentioned. Probe showed it was just the cooked 741 buggering up the filter stage.

So -- thank you to everyone in this thread. It certainly helped me out.

[Uncle Krunkus]

Ah, yes! Of course!!
If the wall-wart you're using is not regulated, it will put out significantly higher voltage when you are using it at a significantly lower current than it's rated current. Know what I mean?
For example,
you have a 9V DC wall-wart rated at 500mA, and you use it to power a circuit which only draws about 40mA, (probably very close to the situation you tried). The voltage will actually be up around 15V, maybe even 18V. If, however, you draw 400mA from it, the voltage will drop down to about 9V. That's the main reason we use "regulated" power supplies.

[reve]