Marketplace score - Aion FX RAT Clone

Che_Guitarra

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Hi all. In the hunt for a ProCo RAT, I came across a Aion FX RAT clone on Marketplace.

Scored it for free off an older guy who I guess lost patience with it, so I thought I would try to get it working.

Components look pretty decent, soldering looks OK too, so plan is to pull it out and rehouse in something slightly bigger, and see if I can work out what's going on. I may need the help of TDPRI along the way :)

First things first - i've downloaded the Aion Helios user guide, i'll confirm the values of all the components, and go from there.

5YONuYS.jpg
 

Che_Guitarra

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OK. Circuit is now out of the enclosure.

I have a few areas to start troubleshooting.
- documentation shows of a third pcb that I didn't receive with this pedal. I think it's safe to leave out, just assisting with lead dress.
- shorting jacks have been used. Not sure if this is a problem or not? Never used them in a pedal before.
- one of the pots has had a wire come free.
- sweep control has a bridge across two of the pins. I'm guessing this is an attempt to omit from the circuit?
- one side of the pcb seems to have been shaved off. I'm guessing to fit into the enclosure. Doesn't appear to have cause any trace damage.

Otherwise, pedal is passing signal in bypass mode, and values of components all seem to be correct, and installed in the correct locations.

I'll buy a new enclosure on the way home from work tomorrow and see if we can get this bad boy up and running.
 

mjcyates

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Not sure what third pcb you are referring to. There should only be 2 from what I can tell. Yes the jumper on the sweep control is to omit it from the circuit, supposed to jumper pins 1 and 2 of the pot.
 

JuneauMike

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A couple of things that I haven't seen you mention. I'm assuming that it does nothing when engaged? However it passes sound in bypass, as you said.

Voltages will usually tell the story. I don't see where Aeon gives you voltages, however GGG's version of the Rat does provide that. http://www.generalguitargadgets.com/pdf/ggg_rodent_instruct.pdf
You can put power to it via a breadboard.

Also, my experience with transistors is that they are finnicky and sometimes not the correct ones for the job. But I don't have a good way of auditioning transistors. Looks like the Aion uses a 2N5458, which is pretty readily available. Maybe confirm what transistor they are using.

The sweep pot weirdness is an easy fix and that may in fact fix your problem.

And then, consider spending some time making an audio probe. That will help you pinpoint where the signal is stopping. https://guitarpcb.com/wp-content/uploads/2018/08/Audio-Probe-Explained.pdf
 

Che_Guitarra

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So it seems there are two build instructions. I downloaded the other and yes indeed - looks like the correct one for this kit.

Has now been transferred into a larger enclosure, following instructions as found above. Externally, plain and simple like a classic RAT. I'm not wanting a RAT plus, so the Sweep option will stay deleted. I'll keep the clipping switch but leave it inside.

Transfer complete, but didn't manage to get it going. Passes signal in bypass. IC replaced with a new OP07 (and LM308 bought too) just to make sure. IC voltages measure in the ballpark of the GGG link above. Replaced the J-FET too with what I had on hand (2N5457). LEDs lighting up, diodes all correct orientation, all solder re-heated to eliminate cold solders, no obvious wiring glitches, no obvious component errors. I wonder if the PCB edge that has been shaved off has damaged a trace? Hmmm.

I'll put it away for a while and come back with fresh eyes.

fqZIGad.jpg
 
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JuneauMike

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How did you wire the switch?
Is a white wire going to the output jack? What is it?
It looks like something is soldered to the middle pad of the PCB out group. What is it?

If your initial gut shot isn't accurate anymore then post what you have.
 
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Che_Guitarra

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Problem solved. A fresh look, and a fresh consideration of the variables, I saw the issue straight away - I had the jacks wired the wrong way to the board. Gee - my eyes are getting bad!

Anyways - up and running, and sounding great! Took out the OP07 and went with the OG LM308. LED clipping mode selected. Good to go. Boosts really well with my other mid-heavy drive pedals. Falls back into the mix pocket when used alone. Exactly what I wanted.

Will get a better chance to dial it in later today across a few guitars.

fIblzbG.jpg
 

jman72

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Awesome! I built one of these a few months ago and I love it. I included the sweep control on mine, but I actually have never used it- I like the standard three controls. I do like the diode switching option, though. Red LEDs sound really cool in this circuit.
 

Che_Guitarra

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Great pedal! A match made in heaven with my new Princeton build.

But my work is not done yet - a bit of squealing going on at higher volumes. Googling it, and seems like a reasonably common issue with DIY Rats.

I'll tidy up the lead dress and shorten as best I can. Hopefully that will be the cure.
 

zippofan

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Glad you got it going! Rats are fun, I've had a BYOC for awhile and my son has a Mr. Vermin from Chicago Stompworks. I wanted to build some classic dirt pedals into mini boxes, and a generous person here sent me a couple LM308 cans so I bought a couple of Madbean's Rat boards "Runt" and had a ball. The Rat always reminds me of playing back in the 80's, my best friend and guitarist (I'm a drummer) plugging in his SG to a Rat and a big Peavey or Music Man and that thing roared :cool:
 




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