help requested - i mightve really screwed up bad

[tone4days]

so, i decided the rehouse my hermida zendrive that i paid a gazzillion dollars for (USED!)  back when the mania was high in the mid 00s

i have a pedal board with all the I/O on the back instead of L/R and wanted to integrate this (awesome sounding) pedal

so i carefully (or so i thought) disassembled the pedal, carefully documenting where all the wires went among the components (including the gooped circuit board),  made a new enclosure, and went to put it all back together when i noticed that i somehow managed to fail to label two wires attached to the circuit board

i am pretty sure that they are power and ground

how can i determine where they go?

can i try it one way (i.e. hot to 'this' wire and ground to 'that' wire) without damaging it?

if i get it wrong (it's 50/50, so that guarantees i will get it wrong on the first go), then i can just swap 'this' and 'that' and be sorted?

any other easier , sure-fire way to get it right?

thanks
t4d

[EBK]

Post a picture

[tone4days]

ok, thanks
let me try to get a pic (man, it's going to be embarrassing)

t4d

[EBK]

ok, thanks
let me try to get a pic (man, it's going to be embarrassing)

t4d

You're here for help.  We're help to help.  It's safe to push your worries about being embarrassed aside. 

[tone4days]

i am positive that everything else is wired correctly to the i/o, power jack, LED, and switch (i even powered it up with no signal to see if the switch turned the LED on/off and it did)

it's just the wire at the top and the little wire in the lower right that i am unsure of

thanks in advance for any assistance you can provide

cheers
t4d

[EBK]

What exactly are the three currently hooked up wires connected to?

From the pictures I've looked at through a Google search, the free ones both appear to be grounds, but I'm not sure....  Can you post a pic of the bottom?

By the way, there is plenty of info available to build another if you fry this one.  Here is just one example (the docs contain the schematic, which may be helpful here): https://aionelectronics.com/project/azimuth-hermida-zendrive-overdrive/

[tone4days]

one of the wires goes from the input signal from the switch  to the goop

one of the wires goes from the center lug of the volume pot to the output side of the switch

one of the wires goes from the volume pot lug to common ground

i'm pretty sure i need to find a way to get 9VDC to the circuit board

also, i left the battery holder out of the circuit as i only use the pedal with the pedalboard's power supply

[EBK]

Looks like we just need to match the pads to the schematic based on what parts they connect to on the board.  My suspicion is that the lower-right wire is ground, and the upper-left is +V.

[tone4days]

thanks
i'll try that and report back

i might try to use my multimeter to see if there is connectivity from either of those wires to the power pin (Pin8)  of the IC or ground (pin4), but i know that in-circuit, connectivity tests can be misleading ... we'll see

[Kipper4]

If you meter one of the wires you suspect of being the + or - rail and the ground and positive pins of the chip that should clear it up.
Check the chip pinout first.
No?

[EBK]

If you meter one of the wires you suspect of being the + or - rail and the ground and positive pins of the chip that should clear it up.
Check the chip pinout first.
No?

Good idea.  Pin 4 should be ground, and pin 8 should be +V.

[thermionix]

(Assuming you did get everything else wired correctly...)

The short wire, if that connects to the negative side of the electrolytic cap in the top right in your pic, that's most likely ground.

If you don't yet have 9VDC running to your board, that's almost certainly what the other wire is for.

There's enough exposed (not gooped) that you should be able to get this sorted out.  More pics, including the other side of the board, may be helpful.

[maartendh]

Have a look at the schematic of the zen drive:
http://revolutiondeux.blogspot.nl/2008/05/zendrive-project-at-fsborg.html (hope this is the same as yours, or at least, close enough)

Observe that there is only one 100K pot, for Volume. The first pin is connected to ground, ignore the middle pin, the third pin is connected to R3, a 1K resistor, This should enable you to find ground. You even can verify this by checking wether ground at the volume-pot is connected (use a multi-meter) to ground at one of the electrolytic capacitors (I think I can see a light blue band with 2 symbols "0" to denote the ground connection on one of your electrocaps).

If this latter cap is C1 in the schematic (it should say 100 uF), the the other side of this cap is connected to the pad where your + wire  should go.
Hope this helps,
maarten

[tone4days]

thanks for the pointers folks - tracing connectivity of pin 4 of the IC to ground was the key

i got it sorted - works fine now

i was going to post a pic of the underside, but realized that there is a thick foamy sticker covering it so you can't see the traces


now, onto my crunchbox clone kit

cheers,
t4d

[EBK]

i got it sorted - works fine now

Fantastic! 

[duck_arse]

i might try to use my multimeter to see if there is connectivity from either of those wires to the power pin (Pin8)  of the IC or ground (pin4), but i know that in-circuit, connectivity tests can be misleading ... we'll see

this. the first thing to do, and all you need. and well done. maybe change that V+ wire to red instead of black? call it "specially modified" then.