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 Post subject: Mouse - No power on pcb
PostPosted: Sun Jun 03, 2018 2:32 am 
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Hello,
as requested from another topic i've opened a new one here. Short summary:
Finished my mouse build, bypass works, but when i switch to ON nothing comes out and LED is off.
I've already measured all the wirings and connections of the switch & jacks, they seem to be fine.
On ac jack: 9V betweed pos and ground.

but on the pcb side there's 0V between pos and ground. the problem is that ground has also 9V, compared with ground of ac jack. in fact i'm measuring 9V everywhere, on the whole enclosure, pcb ground, OUT pad, tip of output jack. However, there is NO connection between POS and ground on the pcb!
i cannot figure out if there's a short between POS and ground or the pedal is just not properly grounded.
do you have an advise how to proceed from here?

plz find some more photos here:
https://www.dropbox.com/sh/bboogx8c2qku ... zuo_a?dl=0

oh, and stereo input jack seems to be fine, since measurements are the same as on my other stereo jacks.
thx a lot in advance


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PostPosted: Mon Jun 04, 2018 9:23 am 
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Power jack wired backwards?


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PostPosted: Mon Jun 04, 2018 9:38 am 
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You're certain that you're not using a power supply with a center-positive plug, right?

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PostPosted: Mon Jun 04, 2018 10:27 am 
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DC jack and power supply are center negative. Also, DC jack is wired according to manual (center pin to "rectangular metal pad" ).

with power supply connected, i get 9V between DC jack ground and pcb POS. i also get 9V between DC jack ground and pcb ground.


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PostPosted: Tue Jun 05, 2018 11:18 am 
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Here's another mystery: how are you even getting any voltage readings without a plug in the input jack?

Please take a pic where your jacks are stretched out so we can clearly see how you have this wired.

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PostPosted: Tue Jun 05, 2018 12:23 pm 
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I've added some more photos here:
https://www.dropbox.com/sh/kav5bgeyu76s ... 2ty2a?dl=0

I hope they'r good enough.
In the meantime i've re-soldered almost every solder pad and cleaned the pcb as good as possibe (removed flux, watched out that no solder making a short from pad to pcb). Issue still exist.


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PostPosted: Tue Jun 05, 2018 1:08 pm 
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Remove the chip and see if it still reads the same

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PostPosted: Tue Jun 05, 2018 2:06 pm 
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Unfortunately yes, still the same.


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PostPosted: Wed Jun 06, 2018 10:07 am 
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Well...you have a short to ground somewhere. That's the only possible explanation for what you are experiencing. I though it would be the chip. It's possible for an IC to have an internal short. If it's not the chip, then you must have something shorted out along either the POS wire, or the POS trace on the PCB. Follow that trace. It could be something you did. It could be a manufacturing defect on the PCB. Look for places on the trace that look like they weren't etched properly. I've also seen something like this once where a tiny piece of wire strand was stuck underneath the chip socket and causing a short, and there was no way to see it.

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PostPosted: Fri Jun 08, 2018 1:30 pm 
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Thx for your support, i'll keep trying to find the short. till now i could not find a contact between POS and ground anywhere on the pcb.
maybe one question:
right above the POS input there are 3 resistors, from left to right 47R, 1M, 1M. the middle one shows connection to ground on both sides.
is this normal?


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PostPosted: Fri Jun 08, 2018 5:12 pm 
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Tschambda wrote:
...right above the POS input there are 3 resistors, from left to right 47R, 1M, 1M. the middle one shows connection to ground on both sides.
is this normal?


The middle one is R1, as shown in the second labeled PCB diagram in this thread: viewtopic.php?f=50&t=39385

Image

Looking at its position in the Mouse schematic (below) in that same thread, you'll see that it connects to the circuit input on one side and to ground on the other. Now if you check the input side of R1 when the footswitch is in the bypassed position, the input is connected to ground through the footswitch. So if you checked that resistor while the footswitch was in bypass mode, you would indeed expect to read ground potential on both sides.

Image

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PostPosted: Wed Jun 13, 2018 12:36 pm 
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R10/47ohm is small enough that it would be like a short to ground if the other end was shorted to ground. So check possible solder blob shorts between R10, C11, and C18, to ground.

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