Amek Recall problem

[1stproduction]

Hello,

I have an Amek Recall console. For some reason I briefly had a powered microphone hooked up to the mic in on one of the channel strips, with the phantom power engaged on the channel strip. Don't ask me why...

The result was smoke, lots of it. Some call this magic smoke.

I don't know where the smoke was coming from in the console and nothing looks damaged on the actual channel strip upon removal.

Would someone here perhaps have an idea of where and how to begin a diagnostic?

[Wonks]

By ‘powered mic’, do you mean a valve mic with its own power supply?

The output from that will be mic level, so it’s more likely that it would be the mic’s power supply that didn’t like being fed 48v than the console objecting. And a decent PSU should ideally be protected against phantom.

So it may just be coincidence that you got component failure(s) when this happened. You can normally smell if a component has burnt out, and as you’ve removed the channel strip and can’t see or presumably smell anything untoward, the problem may well lie elsewhere.

[Wonks]

Are you still getting 48V power available on all your mic channels?

[Hugh Robjohns]

... I briefly had a powered microphone hooked up to the mic in on one of the channel strips, with the phantom power engaged on the channel strip.

What EXACTLY do you mean by "a powered mic"? Most professional self-powered mics — like valve mics, or battery-powered electrets — are perfectly tolerant of phantom power and would not have been damaged.

I don't know where the smoke was coming from in the console and nothing looks damaged on the actual channel strip upon removal.

You're going to have to look elsewhere then. If there was lots of smoke, the component(s) responsible will be very obviously burnt. I'd start at the internal power supplies and work out from there.

Would someone here perhaps have an idea of where and how to begin a diagnostic?

I'd involve someone who knows their way around a professional console. There is a real risk of doing a lot more damage if you don't know what you're doing...

[Wonks]

I'd check the 'powered' mic and its PSU whilst powered up and unplugged from the console. Just check that there aren't any high AC or DC voltage between pins 1 and 2 and 1 and 3. Whilst very unlikely, there could be a remote possibility there's a fault in the PSU that's allowing a high/highish voltage to feed into the console which has caused a problem. Though I'd have thought any large voltage that could blow phantom power DC blocking capacitors would have caused a lot more damage and that there would be obvious issues with the console operation.

But it takes seconds to check and you can then rule out the mic PSU.

[1stproduction]

Hugh - it was a condenser mic with it's own power supply. I don't know exactly where the smoke came from, but it seemed to emanate from the bottom/center of the console. The digital and VU meters jumped around like crazy when it happened. It would be nice to involve a qualified tech for a house call, but that is unfortunately not an option for me at the moment.

Wonks - the mic and it's power supply have been functioning normally since this event, thankfully. I haven't dared to try powering up the desk again however.

I have had this console for around a decade with zero problems. Then I ordered a Rupert Neve channel strip (from eBay), installed it (and it seemed to be working fine). As I was checking the functions of this strip, I (very accidentally) depressed the phantom power button on the strip, as the mic was plugged in an turned on. After just a few seconds the smoke began and a lot of it, even before I had a chance to switch off the main power supply.

After posing this situation to the seller of the channel strip, they essentially said good luck Jack.

Any suggestions at this point will be welcomed and completely free of any liability, spiritual, moral, or otherwise should they be offered. I fancy that I am just skilled and intelligent enough to not make the problem worse.

[Hugh Robjohns]

Hugh - it was a condenser mic with it's own power supply.

Not much help in clarifying matters... I doubt the mic was the problem, as I said, but it might just help to know exactly what mic are you talking about.

I don't know exactly where the smoke came from, but it seemed to emanate from the bottom/center of the console.

then that's where you need to start looking for damage. I'd suspect a problem on the motherboard, probably involving local power regulation circuitry.

I haven't dared to try powering up the desk again however.

Very wise! You definitely want to find the source of the smoke before powering up again!

I have had this console for around a decade with zero problems. Then I ordered a Rupert Neve channel strip (from eBay), installed it (and it seemed to be working fine). As I was checking the functions of this strip, I (very accidentally) depressed the phantom power button on the strip, as the mic was plugged in an turned on. After just a few seconds the smoke began and a lot of it, even before I had a chance to switch off the main power supply.

That would suggest that the phantom power button connected something to something else that shouldn't have been connected! I'd start by looking for damage around the edge connectors of both the strip and the console, and working back in both directions for circuitry related to the phantom supply.

It's possible that some modifications of the motherboard are necessary to allow the Rupert Neve strip to be compatible with the rest of the console, or that the strip needed some modification to be compatible with the console.

[Wonks]

Presumably it’s the authorised RN strip designed specifically for the Amek Recall as alternative to the standard strip? So it should be a drop-in replacement.

[Hugh Robjohns]

I don't know enough about the Amek desk to make that presumption. Lots of 'drop-in replacements' need some kind of system update or modification first.

Perhaps the replacement module was damaged or had itself been updated.

Perhaps the module installation itself caused damage through misalignment or something...

Perhaps a fault on the replacement module over-stressed other systems in the desk...

A thorough investigation is the only answer, and that will require tech manuals, test gear, knowledge and experience.

[Wonks]

I read up on the console after the first post here was made and there definitely was an Amek + Rupert Neve collaboration to make a RN designed channel strip for the Recall (which was originally intended as a live sound desk).

But there's always the chance the strip may have been modified for use in another console and will now need modifying back to standard.

[1stproduction]

Wonks - yes it is the standard drop in RN strip, no issues with fitment. No issues with function either, including the phantom power with unpowered mics and mics with their own power supply, for a period of days, until the incident.

[Mike Stranks]

I notice that you bought the strip on eBay...

Was it new and from a reputable dealer?

If second-user was any detail of its history given? It may have been modded as has been suggested or the fault you’ve experienced was known and that was the reason for sale...

(I bought a second-user camcorder from a reputable dealer (fortunately with warranty); the camcorder quickly showed up a - for that model - known problem which you wouldn't spot from a quick test. It needed a factory repair/mod for which the dealer took the (considerable) hit...)

Anyways... I hope any damage isn't too complicated or costly to fix...

[1stproduction]

Thanks Mike

It wasn't a dealer no, but an individual seller who claimed not to know much or anything about the channel strip. I found that curious, considering they were selling multiple parts from an Amek Recall console. It stands to reason that, if they were the one who disassembled it, they may know a thing or two about it.

Nevertheless, I pulled the trigger, did my inspection and it's really a plug and play installation. The way the cards are set up, I can't see a situation where they could be installed incorrectly. It was working and sounding great, until I pressed that phantom power button - the button which did work fine up until that point. If there was non-visible damage to the boards on the strip, that could be a reason for the malfunction and perhaps the original seller's console got smoked under the same circumstances! I just don't understand what damage or malfunction on that channel strip could cause such a catastrophic failure.

In any event, this is a rather obscure console, but it sounds fantastic and I intend to find the problem. If anyone has any experience with any console with a similar problem (though not necessarily by way it was achieved), it would be helpful.

My "magic smoke" reference was to some poor fellows story of a toasted desk that I read in some forgotten place on the interweb, some time ago. "magic smoke" meant that the console was in heaven.

[Hugh Robjohns]

It might just be an unfortunate coincidence. The components in the module and console are of a certain age when things are more likely to go pop and release the magic smoke.

But all this speculation won't find the fault.

Difficult and inconvenient though it undoubtedly is, you really do need to have a thorough visual inspection of the motherboard and affected module to try and find the original source of the smoke. If it's a motherboard issue it may well be some distance from the module itself. Check out the main psu while you're at it.

Hopefully you'll find something obvious which can then be addressed. If not I'd cautiously power up the desk without the RN module, check all the PSU voltages and, if all good, check the functioning of the rest of the desk.

If that's good you then have to decide whether to reinstall the original strip or the RN one...

Regarding the phantom power switch, the standard current limiting resistors should prevent anything nasty happening, even with a dead short at the mic end. And if it was working normally beforehand it's difficult to imagine how pressing the phantom button could blow something up... but checking the phantom side of the PSU and any local regulation on the motherboard would be sensible.