EHX - Q-Tron  [schematic]

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celadine
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Post by celadine »

Redrawn, so you don't have to feel like a criminal for looking at a damned schematic:

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Qtron.PNG

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soulsonic
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Post by soulsonic »

Thanks! :D
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Post by RnFR »

:applause: :applause: :applause:


"special thanks to the IP Troll."

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Post by lolbou »

Thanks, bravo!
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Post by modman »

:thumbsup :applause:

Great!
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Post by noelgrassy »

Thanks man! :secret:
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Post by Samba pa ti »

noticed the mini/normal qtron is posted but the micro seems to have a slightly different construction (has a different opamp i believe) it might be an equivelant part but the interesting thing i found is that the IC name (and most of the other part names/values) are printed on the board.

the blue board makes it hard to capture the traces, if photoshop doesnt help il take some new snaps in better lighting.

gallery > http://yfrog.com/0fdscf0237oefjx

https://img15.imageshack.us/img15/3903/dscf0237oef.jpg
https://img10.imageshack.us/img10/6977/dscf0238mmv.jpg
https://img14.imageshack.us/img14/9600/dscf0239.jpg
https://img15.imageshack.us/img15/9656/dscf0241w.jpg
https://img5.imageshack.us/img5/6003/dscf0242y.jpg
https://img7.imageshack.us/img7/3379/dscf0243m.jpg

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Post by SPeter »

Exelent! Many Thanks!
:applause: :D

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Post by toneman »

right on, right on , right on! :applause: :applause:

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Post by candidate »

I have reason to believe that all op amps have 0.1uf capacitors going across the supply rails. Not 0.01uf caps. that's what the note on the left of the schematic means, right?

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Post by Andy2No »

Samba pa ti wrote:noticed the mini/normal qtron is posted but the micro seems to have a slightly different construction (has a different opamp i believe) it might be an equivelant part but the interesting thing i found is that the IC name (and most of the other part names/values) are printed on the board.

the blue board makes it hard to capture the traces, if photoshop doesnt help il take some new snaps in better lighting.

gallery >
I'd be interested in seeing those pictures, but unfortunately, all the image links have expired.

Does anyone still have them?

Is the Micro Q-Tron similar enough for the Q-Tron schematic to be relevant?

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Post by Blitz Krieg »

Andy2No wrote: Is the Micro Q-Tron similar enough for the Q-Tron schematic to be relevant?
there are essentially two differences. the mini runs off +/-4.5V. and it has a zener in the envelope rectifier section thingy.

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Post by ksenanekro »

hi there guys

i've bought this "not working" Qtron for 30 euros.

i thought i should post those pics cause i didn't found any gut shots of this one anywhere.

i've found some differences compered to that schem, but got lost.
seems like the one i have on hands, mixes the sides of the ic's in some way i can't understand.

i bought it just for the parts but...
i would love to give it a try and fix it.

...and if someone more experienced is willing to help i would be very happy.

HERE WE GO..
i've re-wired footswitch cause it was about to fall apart and i'm about to change gain pot too.
it passes the signal when it's on, but there is no filter there.
voltages look good at all ics pins
all pots seem to do "something" but as i said there is no effect.

SO...

the strange thing is that when i bring my hand near the pads where there is a place for that dpdt switch under the sweep switch, it acts like a theremin and effect comes alive somehow. as i move my hand on those pads, there is wah wah effect that changes according to my moves.
the same thing happens when i approach the back of that sweep-responce-drive switch.

are my optos dead or something?
i've tried to trace the signal but as i said i got lost cause i think that this board uses the ics's sides in a different way than the schem posted.
thanks for any help
Attachments
_DSC9438.jpg
_DSC9437.jpg

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Post by Andy2No »

Thanks, Blitz Krieg and ksenanekro. I've only just seen those replies.

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Post by Andy2No »

Did you get it working, ksenanekro?

I can see three electrolytic capacitors on the underside of your board. I'd replace all of those - same capacity, and at least the same voltage rating, preferably higher.

When I first read about putting your hand near it and getting an effect, I was thinking of "hand effect" which radios can suffer from - the original theremin was based on that, I guess. Possibly you're just reflecting the light from the LED though?

I'd consider replacing the LED. They can have a fairly short life. Look for dry joints, and resolder them too - with proper 60/40 tin/lead solder, not the crappy new lead free sort.

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Post by howmuch »

ksenanekro wrote: 08 Oct 2015, 11:22 i've bought this "not working" Qtron for 30 euros.
Is that some version of a Q-Tron?
It looks a lot like a Q-Tron+.
Edit: Sorry, I just noticed that the Q-Tron+ is the "Same design as the original Q-Tron but with extremely useful Effects Loop and an Attack Response Switch".
From those photos, it looks like they share the same PCB, with the Q-Tron having un-populated parts (FX loop and Sweep Up/Down switch).
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Post by Leder »

Hello, im working on fixing a Q Tron like this. Im following the signal and i hace no signal before the rotary switch that controls the boost. Is there a chance that the rotary stop working. Can someone tell me how can i test the 2p2t rotary with a multimeter?

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Post by kiltro »

Leder wrote: 28 Jun 2021, 13:19 Hello, im working on fixing a Q Tron like this. Im following the signal and i hace no signal before the rotary switch that controls the boost. Is there a chance that the rotary stop working. Can someone tell me how can i test the 2p2t rotary with a multimeter?
Like this you mean the blue pcb?
Cause it seems to me that its not the one in the schematic in first post.
Blue pcb have 2 separate ldrs while the scheme above have a double one (maybe)?

Can someone confirm this? What was the double-ldr used in the old q tron version?

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Post by MrKuryakin »

This thread caught my interest lately. New to electronics and trying to learn.

Fault finding on my Micro qtron. It seems my D2 was faulty (MMBD4148S). The ground plane was giving me 1.5v drop from +ve dc, and between - ve dc and D2 was 8v drop. Removing the diode it read the same resistance in both directions.

Anyway, does anyone know if can I put any mmbd4148 in there or does it need to be mmbd4148S? Or even if it can be another diode as its only using 2 of the 3 legs.

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