3 Sparkle Boosts but somethings wrong. =(

milkwasabadchoice · December 27, 2006, 01:31:38 AM

OK guys so i built 3 new sparkle boosts for friends and myself and they all biased up correctaly and after a day of sitting in the garage they dont work. the signal is weak and thin. I am using J201's. I checked the bias again and it had changed! Something is going on I just dont know what. Then tonight I tryed to use one again and it crackled and poped when I turned it on, like some leads were touching, but when i took the back off they same thing happened. Anybody know what I need to do to make these things stable and useable?

Thanks a bunch,

Jason

P.S. A friend of mine is going on tour and needs it by thursday so I would love to solve the problem tomorrow. Again thanks for the help.

jonathan perez · December 27, 2006, 01:35:21 AM

check the batteries

Barcode80 · December 27, 2006, 01:41:10 AM

yeah it sounds like you may have wired the power switch part of the stereo jack accidentally to always on and drained the batteries.

milkwasabadchoice · December 27, 2006, 11:40:59 AM

Im running them off a power supply only. So that cant be it. Could it have something to do with the cold weather? I dont know what a leaky transistor is but could that be it also?
Thanks Jason

Meanderthal · December 27, 2006, 12:12:53 PM

Does your garage happen to be really cold? Still, it's not germanium... not sure that would apply so much to Jfets.

Also, I'm not familiar with the circuit, but if it has any electrolytics in it I'd check those.

MikeH · December 27, 2006, 03:52:55 PM

If you're getting crackling and popping when you're taking the back on and off, it sounds like you probably need to shield your circuit board from the enclosure. Don't know how that would effect the biasing though. You might want to follow the "DEBUGGING - When it doesn't work" protocol.

markm · December 27, 2006, 06:22:41 PM

My thoughts are that the cold is probably not a factor especially with Si transistors.
Sounds to me like there is some sort of contact with the trace side of the board like the backs of the pots etc.
I could be wrong but sounds logical to me.

milkwasabadchoice · December 28, 2006, 12:45:44 AM

When the board is suspended in mid air by the wires it still does it. The board is sheilded fine when closed up. It will work some of the time then crackle and pop then gradually get quieter again and work fine for a bit. I just cant figure it out and all 3 seem to have similar problems.

I reallly need to figure this out so thanks to all who have contibuted and to all who hopefully will.

-Jason

Dragonfly · December 28, 2006, 12:57:12 AM

thats odd that youre getting the same bad results with all 3 SB's. Thats the first time i've heard of these issues. MartyMart got a run of bad pots...did you make sure that the trim pots resistance values are staying stable ?

AC

ubersam · December 28, 2006, 01:07:21 AM

Quote from: Dragonfly on December 28, 2006, 12:57:12 AM...did you make sure that the trim pots resistance values are staying stable ?

My thoughts as well: trimpots drifting. May be because of the cold. I have been replacing trimpots with their fixed value equivalents just to avoid any drift problems down the road.

markm · December 28, 2006, 07:17:47 AM

Quote from: ubersam on December 28, 2006, 01:07:21 AM
Quote from: Dragonfly on December 28, 2006, 12:57:12 AM...did you make sure that the trim pots resistance values are staying stable ?
My thoughts as well: trimpots drifting. May be because of the cold. I have been replacing trimpots with their fixed value equivalents just to avoid any drift problems down the road.

A very good thought.
Perhaps the problem is an electro that went belly-up?

MikeH · December 28, 2006, 11:14:56 AM

Yeah, that's my next thought. Did you use any electrolytics that were possibly a little old? Also check their orientation, obviously.

milkwasabadchoice · December 28, 2006, 10:51:51 PM

All the parts were fresh order from small bear. I will check the trim pots next to see what goin on with them, but would that cause crazy crakling sounds? And remember that comes in and out.

Thanks for the continued input guys. Really thanks. Wouldn't be here without you.

-Jason

petemoore · December 29, 2006, 12:12:58 AM

Im running them off a power supply only
Here's one thing common to all three...perhaps try a different power supply?...batteries always put out clean DC.

Meanderthal · December 29, 2006, 11:03:36 AM

Good point! Is it a regulated power supply? If not, all kinds of weird things can happen, and the evil spector of noise is always lurking round the corner...I always test my builds with a battery first, not because I don't trust my power supply, but because it's in a sack with the pedals I use for band practice and gigs...

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3 Sparkle Boosts but somethings wrong. =(