Anderton's Noise Gate problem

[Akuma60]

I there! (first topic ever)

It's been a couple of months that I've been into DIY stompbox, made a couple of successful effects but now I get a really weird problem!!  I'm working with the Craig Anderton book, old school but has a couple of nice effects!  Here's the problem :

I'm building the Noise Gate which is bipolar, so it uses two 9 volts battery!  When I plug everything the second battery (the one with the + grounded and the - going to the - of the board) gets hot and the potentiometer is smoking, I mean really smoking (the pot is really hot and smoke comes out of it !)

Does this sort of problem ring a bell to somebody?

Thanks

[oldrocker]

I'm no expert on the subject but I read earlier on a thread where someones pot was smoking.  It was because there was 9 volts present going to the pot.  Un-solder the pot and fire it up and check voltages on those pot wires.  If one or two of the batteries are getting hot then there's a possiblity that the negative and plus sides of the battery is shorted together.  Like I said I'm no expert but since nobody else chimed in I thought I would see if I could help.

[jimbeaux]

I've built a couple of them & they work fine.

[MikeH]

Pot smoker eh?  Yeah, this happened to me about a month ago. I had a bad solder sending 9V directly to the middle lug of my volume pot.  (Doh!)

ps- that pot may work now, but will get very scratchy and eventually fail.

[Mark Hammer]

Sounds to me like somehow the full current of that side of the supply line is going to the pot.  Ordinarily, there wouldn't be enough juice in the battery to do that to a pot...UNLESS there was a very low-impedance path between that side of the supply line and ground, and the path ran directly through the pot.

[MetalGuy]

I've built a couple of them & they work fine.

This is my favourite noise gate - i've built 5 or 6  without experienced such problem so far. If you try using a single /artificially split/ power supply you'll run into problems though. use MAX1044/ICL7660S or zener diodes.

[Akuma60]

Thanks for the replies!!

I was out of the country this last week so I couldn't thank you earlier!!

I found out what was wrong, I followed the middle lug thing and there it was!  There's a mistake in the layout suggested by GGG (the one that can use NE5532...).  It sends the middle lug (K PCB pad) to the 4 lug of the IC2 when it must go to the lug 3.

Since I corrected that, no hot battery, no smoking pots!

Now I've got another question!

When I use the noise gate, I get a major volume drop, sure I don't get any noise...I can hardly hear my guitar!!

Suggestions ?  I use the NE5532 for the IC1 and LM741CN for the IC2 (since I couldn't put my hand on either LM301, LM201 or LM748)

Thanks

[john101804]

hi brother,

take a look what I find in the GGG layout of the Noise gate and I made some pcb layout corrections: of both IC1 & IC2

[Mark Hammer]

Good eye!

Whenever I'm checking over a layout or an etched board, I always ask myself "Well why would it go all the way over there when all it has to do is connect over here?"  That's a good question to ask for identifying unintentional solder bridges or imperfect etches or, n this case erroneous layouts.

[john101804]

yes bro,ur right me too..

[deadastronaut]

well spotted...good catch, 

i guess the guys who actually built a few did their own layouts....

[jimbeaux]

The ones I built were kits (PCB + parts) from Godbout electronics - used an LM741 and an LM4739 (obsolete) - this was a while back (1978)