Aion Refractor issues after 12v psu

[steve25]

I wanted to test my first pedal build, seems I picked 12V psu from my USB disk instead of my old pedalboard 9v PSU. 

Replaced IC1 & IC2 fixed a few issues. Measured all pins from IC1, IC2 & IC3 and the voltage values are consistent with the manual reference values.

But there is still something wrong with the gain section, it has a high frequency constant noise when you turn the gain pot past 2/3.

Any recommendations what to replace next? Thank you!

[Marcos - Munky]

First of all, welcome!

A wrong power supply shoudn`t cause any issues. I mean, 12V is usually ok for guitar pedals, and I believe this one have a reverse polarity protection diode. But anyway.

High gain oscillations aren't rare on overdrive/distortion pedals when the gain is set high, and can be caused by a number of things. One of them is the enclosure, are the board inside a metal enclosure, and is the enclosure connected to ground? Another cause is the wiring, how are your wires?

Post a few pictures of your build, they'll help.

[idy]

Refractor is a Klon with 1044 charge pump. They are guaranteed up to 10v. Giving it 12 volts meant it was trying to produce -12v and +24. Not good.

Whining is often caused by bad or *substandard* 1044s. Not all are created equal. And over voltage cooks them.

[aion]

Try replacing IC3. If you used a TC1044, those are good to 12V, but they are very intolerant of even a tiny bit of overvoltage. The Z1 zener should protect it, but those have a tolerance that lets them go very slightly above 12V so it's still possible to fry the charge pump.

[Kevin Mitchell]

Some datasheets show the 1044/7660 chips are only rated at 9v max supply voltage! But most that I've seen go up to 12 (that was close, wasn't it??).

I have only had headaches from using anything other than an LT1054 for voltage pumps & inverters. That likely depends on the intended circuit as well as the manufacturer of the subjected IC.

[MikeA]

+1 on replacing IC3,  there's a 12V zener protecting it, but depending on the exact brand and model, it might be damaged anyway.  The Microchip TC1044S tolerates up to 13V, but Maxim MAX1044 only tolerates 10.5V.

[steve25]

Wow, thank you for so much feedback. I'll order a new TC1044S & LT1054.

[MikeA]

Wow, thank you for so much feedback. I'll order a new TC1044S & LT1054.

It's always a good idea to check the data sheets when you substitute IC's.  In this case, IC3 is specified as a TC1044.  An ICL7660S is pin-compatible and would work fine.  An LT1054 has a different use for pin 1 (shutdown rather than boost) and requires an outboard transistor for reliable start-up when using both +18V and -9V outputs, as you are here.

[aion]

An LT1054 has a different use for pin 1 (shutdown rather than boost) and requires an outboard transistor for reliable start-up when using both +18V and -9V outputs, as you are here.

I don't have the reference handy, but someone contacted Analog Devices awhile ago about pin 1 being jumpered to pin 8 and their response was that it wouldn't change the functionality at all. The LT1054 doesn't have the frequency boost feature (it's already boosted internally) but it should be a drop-in replacement for the 1044 even if the PCB layout includes the frequency-boost jumpering.

The 1054 is also pretty commonly used in the Centaur circuit for +18/-9V and I've never heard of it needing a transistor to buffer the voltage. That's just one circuit (although a popular one) so it may come down to how much current is being drawn from the charge pump. But again, anecdotally, the LT1054 should work just fine here with no other changes, if not even better than the TC1044.