Testing a Battery Snap

Started by MustangMartigan, January 19, 2018, 02:54:10 PM

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thermionix

I know it's been covered above, but you did have an instrument cable plugged into the input jack, right?  That's the left one in your picture, I ask because it's easy to get them backwards when the pedal is upside down.  We've all done it.

Tony Forestiere

I think Therm has this point. Not seeing a plug in the input now on the left side.
( I like the shirt too!.)
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MustangMartigan

Quote from: Tony Forestiere on January 23, 2018, 06:16:29 PM
I think Therm has this point. Not seeing a plug in the input now on the left side.
( I like the shirt too!.)

The picture of the Wah was taken a few days ago. Battery was securely snapped in it's snap, instrument cable was definitely in the instrument input.

What's so wrong about the numbers that makes you guys feel I flubbed the test? Are you guys sure that 20 is the correct DCV setting?

thermionix

You had your meter set correctly, but the voltages on your transistors are way low, almost zero.  There's a cap, diode, and resistor all next to each other over by the DC jack.  I'm going to guess one or more of these components is bad, maybe from being exposed to reverse voltage.  With your meter's black probe still on ground, circuit powered up, see if you can find 9VDC anywhere in that general area with the red probe.

Tony Forestiere

I thought this to be weird. Square peg in a round hole? The DC jack looks "jacked". Lots of daylight showing. Could have been kicked and have broken connections/traces on the pad side, causing power issues.
Just a guess. You won't know until you remove the PCB.

"Duct tape is like the Force. It has a light side and a dark side, and it holds the universe together." Carl Zwanzig
"Whoso neglects learning in his youth, loses the past and is dead for the future." Euripides
"Friends don't let friends use Windows." Me

duck_arse

Quote from: MustangMartigan on January 23, 2018, 06:31:48 PM
Quote from: Tony Forestiere on January 23, 2018, 06:16:29 PM
I think Therm has this point. Not seeing a plug in the input now on the left side.
( I like the shirt too!.)

The picture of the Wah was taken a few days ago. Battery was securely snapped in it's snap, instrument cable was definitely in the instrument input.

What's so wrong about the numbers that makes you guys feel I flubbed the test? Are you guys sure that 20 is the correct DCV setting?

far from flubbed. you have some valid data there. it shows that there is no supply volts reaching the circuit. this could be because:
- there is no supply switched on because of a missin jack plug
- the batter snap is bad
- the DC jack-switch is not shorting when no dc plug inserted - broken or corrosion
- you didn't turn the meter on

let's ignore the last one. you fix the first one by inserting a plug into a jack, whichever is the supply switching one. you prove/disprove the snap by making continuity measures between the snap lugs and the board. if that test proves good, you have also proved the DC jack. dis/prove the DC jack by measuring the resistance between the battery snap (+) and board as you plug and unplug a DC plug [*NOTE - an unpowered plug, you just want the plug itself, not the supply it provides*] to work the socket contacts.

I think you should away your battery for the moment, and JUST do continuity/resistance measures, to find what is not continuousing.
" I will say no more "

thermionix

Quote from: Tony Forestiere on January 23, 2018, 10:09:29 PM
Lots of daylight showing.

That's normal for these Crybabys, the DC jack is only mounted to the PCB, not the enclosure.  I think the problem is probably in that area, shorted or open component, or a problem with the DC jack.  I would be probing for 9V, see how far it makes it.

pinkjimiphoton

just use the diode check/ continuity function of your meter. one side of the stock baby switch is the input. the other two are a or b output. you'll have to figure out which is which, but two of the connections will beep. push the switch, and the other connection and the common should beep.

no beep? bad switch.

but i suspect your board may be shorting to the crybaby case. that's happened to me before. sometimes the switching jacks will develop enough corrosion to actually kill the wah, too. but most likely, its the switch like you already suspect.
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vigilante397

Unfortunately the meter he showed initially (if it's the same one I had from Harbor Freight) doesn't beep on continuity :(
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