AR2412 Noisy input. Schematic / parts list, etc, available?

Other A&H Products
1

Hi. My AR2412 (purple faceplate) has recently developed a noisy input channel (#6). I use it with an SQ6.

Noise level varies with preamp gain. It is passing signal, but the noise is bad enough that I’d originally thought it was a broken / misconfigured wireless receiver. It sounds like bad FM static with a bit of lightning storm thrown in.

I’m patching around it until my next gig, but want to repair it ASAP afterwards. Either component level, or a board swap.

I haven’t been able to locate a full parts list or schematic. Does anyone have one?

I trolled around on Full Compass, and found this.

Allen & Heath 004-400X Audio PCB for AR2412 | Full Compass Systems

If you can’t follow the link, it is accompanied by a blurry photo showing 8 XLR ins and 4 XLR outs, and edge connector, and a number of electrolytic caps (looks like three per channel) near each grouping of what I assume are A/D, preamp, and gain control (or buffer amp?) SMD ICs.

I don’t feel like cracking it open until my next show is over, but would like to take a stab at a localized repair first.

With the problem being isolated to one channel, I’m hopeful that it’s a bad electrolytic cap or something fairly simple. I have desoldering equipment, a cap replacement would be easy. I’m capable of doing some SMD de- and re-soldering if needed, depending on the pin count & style. But I probably won’t go beyond blindly swapping a few caps unless someone can guide me to another likely culprit.

Has anyone gotten near one of these with a soldering iron and/or a scope, and are there any easily swapped items in the circuit other than the caps that might be at fault?

If I fail at that and have to proceed with a board swap…

the AR2412 is 24 inputs, 12 outputs. The 004-400x photo I’ve seen shows 8 input and 4 output XLRs.

Does the AR2412 contain three 004-400X boards (seems likely?), or one board plus some other/different daughterboards for the rest of the I/O jacks?

And… any idea if the audio board(s) would work on all version of the AR2412? Mine is an earlier one, with a purple faceplate.

Any insights would be much appreciated.

Thanks!

2

I can’t answer your question about component-level repairs, but I did take an AR2412 apart to replace the network card, and there are three 8-in 4-out I/O boards in there.

For the network card, I bought a new one and it worked in my purple unit, so I’d say good chance a new I/O board would work with a purple unit as well.

3

Thank you. I’ve now heard back from a few vendors and they agree; qty 3 audio boards, and the don’t care about the vintage/serial number. Hopefully that means they haven’t changed…

Alas, they won’t/can’t share a parts list or service manual. I can (sort of) understand not sharing the schematics/service manual.

But providing a list of the assemblies / part numbers found in the unit seems pretty innocuous, especially given that they are for sale, and are searchable on the Internet.

The audio board cost ca. $300, so attempting a repair seems like a no-brainer… best case, it’s a cap or an SMD resistor and costs me $5. Worst case, I can’t find the problem and it costs $300 for a new PCB.

I have some downtime after this weekend; I’ll tear into it and report back on the results.