Atomic Amplifire 12 - Accidentally fed it 18V...

[jockemedw]

Hi guys!

Might have chosen the wrong forum, sorry if that's the case.

So I accidentally fed my Atomic Amplifire 12 18V (wants 9V). The screen started flickering, went black and after about 3 seconds I realized my mistake and pulled the chord. Afterwards it had a slight "burnt electronics" smell and won't start. I've contacted the manufacturer about it, but since I live in Sweden, the shipping + repair cost won't be worth it. I just figured you might be able to help out with identifying some of the components, so I could try repairing it myself.

I've figured the components in the picture are:

FB1: Ferrite Bead (some kind of noise cancelling funktion) - But I can't find any specs on it.
BR1: A bridge transistor. I can't find an identical one though.
L1: An inductor. Can't find any specs.

Does anyone have any clue if one of the above are more prone to be the toasted component?

I'm thankfull for all the help I can get!

[Jazz P Bass]

Nothing in that pic appears 'toasted'.

Each of those parts can be checked with an ohmmeter.
The bridge may require that you use the 'diode check' function.

[quad4]

My guess is br1. What's the voltage at the output? Input?

While the board is out of the enclosure, can you post some high quality pictures of the entire board and the main ic's. Curious what's driving this puppy, especially the ADC, DAC, headphone driver, effects loop, and the input section.

[Mick Bailey]

Was the 12v supply the correct polarity for the equipment? Reverse polarity is far more likely to cause damage than anything else. Agree, if I was looking for a failure first suspect would be BR1. It can be tested in-circuit using a DMM. L1 looks to be a common-mode inductor. Rarely, these fail open on one side. Looking at the picture you can see how the input voltage runs through this to the two AC ( ~) terminals of the rectifier. It should give continuity on the LH and RH pair of terminals respectively (as viewed in the picture). FB1 is an unlikely failure candidate - it should give continuity across the terminals.

[nevetslab]

Welcome to the Forum!

Seeing the bridge rectifier immediately following the inductor in the layout, I assume this was 9VAC powering, NOT 9VDC.

My guess is your problem is past the filter capacitor C3 (100uF/35V). 9VAC or 18VAC, that would still pass thru L1 inductor, BR1 bridge and the ferrite bead without any problem, and you'd have twice the voltage charged up on C3 than normal. I'd expect there is a voltage regulator to put out stable DCV to run the rest of the amps' IC's and circuits. You would have been feeding about 24VDC instead of around 11.5VDC into the regulator. If the regulator failed, and resulted in passing the unregulated voltage down stream to the rest of the circuits, you have a disaster. We await to see the rest of the circuits in your photos.

[J M Fahey]

Yes, you are showing us just the 3 or 4 supply input components, thereīs way more downstream and of course then thereīs the whole pedal circuit itself.

Your only hope is that some regulator cracked open but nothing further and replacing it restores functionality.

Just to start with something, please upload photos showing readable labels, both from original/official supply and the one you connected instead.

[jockemedw]

Thanks for all of your applies!

Before I choose which response to follow, I guess i should go ahead and give some more info:

- The "other adapter" was 18VDC (+ tip), the AA12 wants 9VDC (see picture).
- Im focusing on the power circuit simply because if it's not the power circuit, I'm probably tossing it...
- The "burnt electronics smell" was coming from the area where the first 4 components are in the original picture.

Album of more photos: https://photos.app.goo.gl/JaYL1Kz1hqeNCixZ6

Sorry for the quality, it would take so many pictures to cover the whole board with good quality.

[J M Fahey]

Ok, one mystery cleared, power jack says "input + or -", probably courtesy of the little bridge rectifier.

As of the 4 components shown first, Iīd follow tracks until a voltage regulator and check if itīs dead.

In principle, we have nearby an IC labelled 3032 N2058 and identified in the silkscreen as VR50 .... "5.0Volt Voltage Regulator?"
IF so, we might check datasheet and check raw (+9V) input, regulated (+5V) output, and whether we have 5V at the output pin or not.

IF itīs bad, maybe replacing it restores functionality.

IF the problem lies on the main DSP board, itīs beyond me; others might tackle that.

[nevetslab]

All the text in the series of photos are upside down, so I haven't tried to import images to flip them and see what the next circuits that are probably voltage regulation. It looks like that RED plug-on wire carries the input voltage, and the not sure where the return ends up. At the other end of the PCB, I see a header that shows a number of supply voltages....+5V, +3.3V, GND, +6V, -5.5V. With 9VDC input, do these voltages appear (need your DMM & probes for that)?

[J M Fahey]

Eagle eye

Yes, it may very well get 9V in, any polarity, and have some smart IC convert that to various voltages, more complex that a plain regulator I expected.

If so, thatīs a definite candidate to "die first" and maybe, protect others (by shorting +18V input) with its sacrifice.

But it should be identified first; Iīd google visible IC labels searching for one which does that, then download the datasheet and start there.

[g1]

Just thought I would mention, this unit is designed to accept any 9 to 12V supply. AC, DC, polarity does not matter.