Tonebender MkIII sounded so nice until I opened it to take a picture

Started by EBK, February 11, 2019, 03:45:18 PM

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EBK

This tonebender MkIII worked the very first time I fired it up.



It sounded so nice too, and I was so incredibly happy.  I decided that I wanted to take a pic of the guts to show them off later, so I opened it back up, snapped the above pic, closed it up, and tried it again. 

Loud continuous buzzing when engaged. 

Initially, I noticed that transistors Q1 and Q2 made some noise if I touched their cases with my finger.  After tapping Q1 (on the right side of the board; Q2 is in the middle) a couple times the circuit seemed to quiet itself down. 
Loose joint I figured, so I reflowed the solder around Q1 and Q2.  It seemed to work again, so I closed the box up.  Then, nothing but loud continuous buzzing again.   :icon_frown:

I tried poking around at things, and now the circuit seems to work again but the audio is very very quiet.  There is still buzzing, but much less.
I don't see anything shorting, and the problem persists when the board is lifted up over the rim of the enclosure.

Any ideas?
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reddesert

Loud buzzing often means your ground is detached. Check the connections at board and both jacks, for example.

SpencerPedals

Quote from: EBK on February 11, 2019, 03:45:18 PM
It sounded so nice too, and I was so incredibly happy.  I decided that I wanted to take a pic of the guts to show them off later, so I opened it back up, snapped the above pic, closed it up, and tried it again. 

Set the pedal to bypass.  Delete the picture while in view of the pedal.  Engage the pedal.  It sounds like it just objects to the picture being taken.

(But really that ground thing mentioned above sounds like the first thing I would check)

amptramp

Are the transistors touching the lid of the case?  If that is the problem, a layer of tape on the lid may solve the problem.

EBK

Quote from: amptramp on February 11, 2019, 05:14:56 PM
Are the transistors touching the lid of the case?  If that is the problem, a layer of tape on the lid may solve the problem.
Already added that tape.  Didn't help.  Well, it probably did help, but it didn't solve everything. 

Right now, I'm filing down the output jack to give the board more room. Maybe if I squish everything less....
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pinkjimiphoton

eric bro, be careful, its easy to smoke them transistors. i must concur with the ground issue, its a fairly common phenomenon in my experience
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Fabeii


EBK

When I last fired it up, with the board propped above the box, it was quiet-ish in a "something is wrong" kind of way.  I've fiddled with it a bit but haven't retested it.  It has not actually been tested completely outside of the box. 
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pinkjimiphoton

never fails. if ya box it before testing, never works. at least for ME lol
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EBK

Quote from: pinkjimiphoton on February 16, 2019, 06:29:15 PM
never fails. if ya box it before testing, never works. at least for ME lol
Nah, this worked perfectly when I boxed it, remember?

Then, I took off the lid, snapped a pic, pur the lid back on, and it quit (more or less).
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pinkjimiphoton

voltages look ok?

sure sounds like the main board ground connection is screwy. i've had that happen a lot of times,  the fuzz will be working, sorta, all the knobs do stuff, but super faint. almost always a bad solder joint to ground for me.
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"When the power of love overcomes the love of power the world will know peace."
Slava Ukraini!
"try whacking the bejesus outta it and see if it works again"....
~Jack Darr

EBK

I'm really hoping it is just a ground connection and not a fried transistor.  I'll check it out with my meter next time I get a chance.
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EBK

Now, this is interesting.

You see those three terminals on the lower left of the switch?  They should all be connected together and grounded.  The two in the bottom row check out fine.  The wire leading up to the second row?  Also fine.  But, no continuity with the actual lug in the second row.  I'll reflow that and report back.  Fingers crossed.

Update:  It was definitely the broken ground connection at that lug causing the problem.  Fuzzy goodness once again!  :icon_cool: Thank you, everyone!  :icon_biggrin:
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Fabeii

Nice catch!
so was the wire from the bottom  just going through the lug without a proper solder joint nor making stable contact?
Impressive!

EBK

Quote from: Fabeii on February 17, 2019, 11:54:51 AM
Nice catch!
so was the wire from the bottom  just going through the lug without a proper solder joint nor making stable contact?
Impressive!
Yeah, the wire passed through the lug, but somehow avoided it electrically.
Everything looked fine, mechanically stable (mostly), and covered in shiny solder.  Quite impressive for a bad solder joint!  :icon_lol:
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