Vox v847A remove input buffer

[wcampagner]

Hello,
Does anyone have a guide to remove the input buffer from the new vox 847A model?
I want to make the seagull Pink Floyd Echoes effect, but i doesn't work in a buffered wah.
Thanks.

[thegnu]

if it's the input buffer when it's off that you don't like, route around it with a 3pdt.  you should be able to just do a true bypass mod for it, but i would google it to be sure.

if you need the buffer gone for when the wah effect is engaged, what with all the smd components and lack of schematic, i'd say your best bet is to buy a crybaby used for $20.  otherwise, just bridge (to preserve the signal path) or remove (to disconnect from ground or 9v) all of the components that aren't in [this schematic](http://www.freeinfosociety.com/electronics/schemview.php?id=617&phpMyAdmin=af0f6b4465fe3f904426eaeb3dc0e3fa&phpMyAdmin=Kb2XHnhmhTctZwPmOqks7zD3-sc)

but i couldn't tell you for sure without more information.

[yeeshkul]

Does it have SMD parts at the bottom side of the board?

[wcampagner]

Hello Yeshkul,
yes, it have.
Thanks.

[wcampagner]

Hello,
i saw your post here:
http://www.diystompboxes.com/smfforum/index.php?topic=83784.0

my vox is very similar with your pictures.

i think this is what i was looking for.
does it worked correctly?

Thanks again.

[yeeshkul]

Hehe, i see i have answered already. I completely forgot. In that thread i was asking for help with oscillation but it was just a broken switch. That failure actually led me to the idea of the Seagull switch pictured in that thread (... and massively overlooked by Gilmour fans here, haha). The picture is perfectly all right i have modded about 20 of these wahs that way ever since. I have ran into slightly different boards (just slightly), so if your board is a bit different just see the part numbers.



Remove R1, R14, R12, the transistor and you may remove L2 as well.
I actually removed R1 because i prefer 47k in there (when TB modded).
I also removed the pull-down R11, because i have a different way of getting rig of the clicks.

[wcampagner]

Hello Yeeshkul,
Thanks for the information.
My board is slightly different... but very similar.
I'll remove the parts and test... i think it'll work.
I'll post the results here.

Let's see if i can get the seagull effect... hahah.
I'm in hurry because i have a floyd tribute band here in Brazil.
And the city hall asked us to play the entire Meddle Album in a few days to celebrate the 40th birth of the album.
I hope we can get all done.

Thanks,
Wagner.

[yeeshkul]

Well then seagull effect is pretty necessary i guess
By the way you can remove the big yellow input cap 10n as well.
I modded the same board you have few times, so yes, it works. Just make sure you removed those SMD parts withou making solder bridges.
I usually heat one end of it and fling it of off the board by a knife. There is a faster way to remove buffer, but this is a clean solution.

[wcampagner]

Hello Yeeshkul,

Thanks again for all the information.



I have just some doubts.

As i just want the seagull effect right now, and i'm in a hurry, i won't change R1.

I'll just remove the other parts... so if i take out the L2, i think i should replace it with a jumper... right?

And the capacitor you talk about, i think it is 100n and not 10n right?

It is the yellow capacitor right in the front of the buffer, right?

In my board it is labelled C6.



Thanks,

Wagner.

[yeeshkul]

Yes i mean 100n, i'm sorry. If you wanna leave the R1 res in, you will have to use a jumper from input to R1 anyway, so i recommend to use a new resistor R1 instead of the jumper (connected between input and C1).

[Joe Hart]

Has anyone figured out what all the parts on this board are (or better still, the V845)? I have a V845 that I really like the sound of, but want to add a little more bass and mids to it and cannot make heads or tails out of most of the board! I don't know which resistor is which. I think the V845 is very similar to the V847A (the V845 has the buffer already removed, I believe). Thanks!
-Joe Hart

[leito79]

I also removed the pull-down R11, because i have a different way of getting rig of the clicks.

Do you mean grounding the input (or output) of the circuit when bypassed at the stompswitch?