Quick Boneyard Question

[pryde]

Hello,
I just put together a fabbed boneyard (new version) and used all stock values including a TC1044SCPA as specified in the build doc. The only sub is 82n in C7 as I am out of 68n right now.

When testing the circuit (unboxed) everything works fine except I get the dreaded high pitch squeel on either channel with the gain pots at 25% or greater.

Is this because it is not boxed-up yet? I plan on using sheilded wire when boxing but want to address the oscillation if possible before boxing it. Did anyone else get bad squeel when testing the pcb before boxing? Did it go away afterward?

Thanks for your insight

[mgwhit]

I breadboarded this circuit today (with only the high gain pot).  The only subs I made were 470pF's for C1 and C4 and a 1n for C13.  I get no squeal at all with the Gain totally maxed out, although it's pretty noisy with no enclosure.  This is (still) a fairly bright circuit and I kept the Tone at around noon while I was messing with it tonight.

Does rolling off your tone knob affect the squeal at all?  I would recommend trying higher values at C1, C4 and maybe C9.  Good luck!

[pryde]

The squeal is still present with the tone knob turned either way. The squeal/whine sound is effected when turning the tone knob but is never goes away.

With the gain on either channel up past 9-10 o'clock the high pitch comes in but is not present when actually playing/strumming. As soon as you stop playing it is screaming like a banshee.

All controls work great and the pedal sounds really awesome otherwise. Not sure if I should just start boxing it up or does this need to be addressed beforehand?

Thanks for any help

[mgwhit]

There's a notorious whine issue with some charge pumps in this circuit, but I think the TC1044SCPA is supposed to be immune to it.  I suppose you've found all the other threads about this -- if you haven't, search for "boneyard" and "whine" and you'll see what I'm talking about.  Earlier I was assuming that that probably wasn't your problem since you specifically said you were using the TC1044SCPA, but I can't help but wonder if you might have a bad one.  Do you have another charge pump IC you can try?  Maybe someone else who has had the same problem can chime in and help you better.

And for the record, I wouldn't box it yet except as a last resort.  It's not the end of the world to unbox, but it's not particularly fun either.

[pryde]

I just popped in a new charge pump (tc1044scpa) with the same results? Not sure what to do next. Gonna pick up tomorrow on this. must go to sleep...

[mgwhit]

Okay, so let's assume it's not the charge pump whine (since you're using the correct version and you've tested two of them).  My best guess is that you're either generating way too much gain or not cutting enough treble, and that there is a bad component value or a bad solder joint somewhere in one of your op-amp negative feedback loops.

To help us along, please post the voltages on each pin of your IC1 and IC2 and well-lit, in-focus, high-resolution photos of both sides of the board.

[gtr2]

I think krock had the same problem.  I forget what his fix was.  You could pm him or you might be able to find the post if you search with his user name.

Josh

[pryde]

OK. back at it. I triple checked all values,  no solder bridges. changed both chips IC1 and IC2 with no results.


Here is something I found. When I just touch the volume pot on the lugs the pedal is dead quiet and works/sounds great. The Vol is a 10kA pot with 10k resistor soldered to lugs 1 and 3. Makes me think it may just be an un-boxed grounding issue? Just touching it (with a little firm pressure) kills the squeal at full gain.

THoughts? I can take some voltages and post pics still if necessary.

Thanks for your help.

[madbean]

It should go away once boxed. If not, reducing the value of the high gain pot as mentioned in the build doc should eliminate it.

[pryde]

All right I will box it up and hope all is well. Not sure about the gain pot though as it does the squeal on both channels (100kb and 1MA pots). I will report back. tHanks for all the help so far.

[crash]

Not to hijack the thread, but I have the same issue.  Here's the weird part: No whine when the hi-gain pot is in the circuit at any level.  When the low-gain pot is in circuit, I get whine when it is over 1/2 rotation.  I am using a 50kB for low-gain and a 500kA for hi-gain pots.  I am using a MAX1044 charge pump. 

I originally had a TC1044SCPA, but then I would get the whine on the high gain pot.

[pryde]

DAMN...

Spent all night boxing it up and it still squeals/whines the same. I used sheilded wire on all pcb and jack inputs and outputs. Not sure about voltages but the LF347 has alot of 0's ? Got the same reading with 2 different chips?

TC1044SCPA:

1. 9.24
2. 5.58
3. 0
4. 3.45
5. 8.8
6. 4.62
7. 4.33
8. 9.24

LF347:

1. 0
2. 0
3. 0
4. 9.24
5. 0
6. 0
7. 0
8. 0
9. 0
10. 0
11. 8.8
12. 0
13. 0
14. 0

[mgwhit]

You didn't show it, but your voltages on TC1044SCPA pins 4-5 and LF347 pin 11 should be negative.  I'm assuming you just missed it because you weren't expecting it, but please go back and check.  If those pins are really negative then, all of your voltages look correct.  The 0's on LF347 are just because the Boneyard uses the +9V and -9V power rails and doesn't have to use a ~4.5V reference voltage (typically labeled VB in other circuits).

I'd still like to see the board, though.

[k.rock!]

Hey dude!

Here's the thread that Josh was mentioning: http://www.madbeanpedals.com/forum/index.php?topic=2290.0

This is what worked for me:

"In my case, I used a 150pF across pins 1 and 8 (I just stuffed it into the socket) and it took care of if. Now, I'm not sure if we have the same problem in common though. The frequency whine I had was very subtle and it wasn't very loud."

I know there has been more people with the same issue but as far as I'm concerned, everyone has solved it one way or another...Just try searching for "boneyard" "squeal" "whine" "plexi" keywords like that and you'll find a few threads discussing the matter...

Hope I could be of better help. Let me know if I can help with anything

Good luck!

-Kaleb

[pryde]

Yes the pin readings are negative that you pointed out. I tried a 100pf cap across pins 1 and 8 on the charge pump with no change at all.

Also, I have read all the posts I could find on the boneyard whine issue. Here is a pic of the populated board. Maybe i missed something but I think all is good?