Rode Shat Itself Mid Session

[Line666]

Recording vocals with my Rode Nt1a today and after a couple of track it started cutting out after five seconds of recording.

Checked everything - switched cables, restarted the pc, tried the session it was working on, changed phantom power banks, changed the channel and finally tried a different mic - which worked perfectly.

Before I noise Rode up for sending it away to get fixed can anyone shed any light on this sort of stuff, has this happened to anyone and is there anyway to easily fix it?

 

[Gonzo666]

could be bad soldering within the Mic or the internal transformer...If it is within the warranty period I would send it to Rode. Mostly there is nothing you can do by yourself...

 

[Sloan]

If out of warranty and you want to check it out yourself, i would start with the XLR connection.

 

[Omega_Void]

could be bad soldering within the Mic or the internal transformer...

NT1-A is transformerless, it uses "JFET impedance converter with bipolar output buffer".

If it is within the warranty period I would send it to Rode.

+1, but "You must register your mic FREE within one month of purchase, at: www.rodemic.com to receive your 10 Year Warranty", otherwise warranty is only one year.

If it isn't covered by warranty...

Mostly there is nothing you can do by yourself...

...unless you can use a soldering iron.

The most common causes of failure in electronics are solder joints and electrolytic capacitors. First questions that occur to me:

... you say it "started cutting out", so the fault's intermittent, yeah?
... how quickly does it come and go?
... does it fade out at all, or disappear just like *snaps fingers* that?
... any crackling noises?
... does it tick over okay on background noise, but crap out when you give it some proper SPL?
... does vibration make a difference?

I'm going to just assume you have no way of measuring the current drawn from the phantom supply, but do correct me if I'm wrong!

I found a thread showings photos of an old NT1-A, there's really not much to go wrong. Resistors, inductors and film caps are pretty damn reliable.

Beyond them there's only two electrolytic caps and three/four transistors, and five diodes.

Two bipolars for the output (and they can't be failing in sync!), one JFET buffer/gain stage.

The other three-legger is either a regulator like LM317, or a transistor used in a discrete regulator circuit. (I assume active regulation 'cos NT1-A is good for P48 or P24 phantom power.)

There's a short limit on what the problem can be. Any reasonably competent person with a multimeter and soldering skills should be able to fix this in pretty short order.

Replacement parts would only be a problem if the JFET's crapped out, for reasons which are pretty boring.

 

[Line666]

The most common causes of failure in electronics are solder joints and electrolytic capacitors. First questions that occur to me:

... you say it "started cutting out", so the fault's intermittent, yeah?
... how quickly does it come and go?
... does it fade out at all, or disappear just like *snaps fingers* that?
... any crackling noises?
... does it tick over okay on background noise, but crap out when you give it some proper SPL?
... does vibration make a difference?

Yeah the fault is intermittent - it seems like it might be an SPL problem but it's hard to say because it usually cuts out at a very specific point - say five seconds after starting to record - there is a slight fade it's not an abrupt change, it's not sudden really it just tapers off, the phrase will normally finish then it will fade out at the - air space if that makes sense. The problem comes and go, say every two minutes or so the mic will decide to start working again then have the same problem. I will have to test it on background noise and vibration I don't know about those two.

Didn't realise the product had to be registered a month after purchase for the warranty - bummer

 

[Omega_Void]

...it usually cuts out at a very specific point - say five seconds after starting to record -

Bizzarro!!! ...Perhaps you mean after ~5 seconds of hollering into it? If it only happens when you're recording I might suspect some sort of evil curse...

...there is a slight fade it's not an abrupt change, it's not sudden really it just tapers off...

Okay, so: you still have some signal coming out after the fault kicks in. Ergo: the wiring between the audio output devices and the XLR is intact.

BTW forgot to put in the link to the thread with the gutshots. Apparently later versions used surface-mount, which makes things more fiddly. The designer also says "The same design and circuit was also used in the original NT-2 mics", and the NT2 schematic is here.

So the fault is in either the audio circuitry, or the power supply to the audio circuits, or the polarising voltage the capsule needs to work.

If you can hear circuit noise when the fault occurs, it would indicate the preamp circuitry is still going fine but has no input (i.e. the polarising supply to the capsule has been lost and it's putting out no signal). In that case look for a bad connection between the capsule and PCB. But I would expect crackling/distortion if that were the case.

I know NT1-A is supposed to very quiet, but I'm assuming you can hear some difference in noise when the mic is powered up than when phantom is off...?

If there's no circuit noise at all to the output, the preamp circuitry has lost power entirely, in which case... Since you haven't mentioned any crackling or distortion when it's working, I'm inclined to think the fault is in the supply at or prior to an electrolytic cap.

(An electrolytic cap across the power supply feeding the audio circuit acts as a reservoir of charge. If the current topping up the cap is removed, the audio circuit drains the cap, but not instantly. As the charge begins to run out, the supply voltage drops gradually, and so does the signal level, normally becoming a bit distorted as it drops off.)

An electrolytic becoming leaky (starting to pass DC) could also have similar effect. Leaky electros are self-healing (damaged oxide layer nabs oxygen from the electrolyte fluid to repair itself) but remain fragile and give out again when current draw rises.

Assuming the mic has remained plugged in when it's crapped out... if it's a bad electro I'd expect it to give out pretty quickly again when called on to deliver current. If it's a bad solder joint I'd expect it to take a while to expand and lose connection again once it's cooled off. If you understand what I'm getting at there?

If it were me I'd open the sucker up; keep it clean, wear latex gloves, don't get finger grease on the circuit board. If you see anything looks melted or smell anything burned that's normally a big clue.

If an electro looks swollen, it's definitely fucked. Google "bad caps" and you'll find pix. Replace and hopefully problem solved.

If the electros are cheap & nasty I'd replace them as a matter of course, and test the old ones for leakage. If they're nice and look okay...

Visually inspect for bad solder joints, reheat any that look dodgy. It's is more difficult to spot with lead-free solder, but you may find one which is obviously fucked. Check for this even if you find a bad cap.

If you found bad cap/joint and fixed: clean off with IPA or switch-cleaner when you're done. Leave it about 10 times as long as it says on the can before switching on the mic.

If you can't find bad caps or joints visually, it's time to plug in with the circuits exposed and start measuring voltages with a multimeter. That's the time when a persistently faulty circuit sits there all day refusing to play up .

This kind of needs to be done by somebody who knows what they're looking at. But assuming that NT2 schematic does reflect what's in your mic, the fault would be pretty quick to pin down when it does occur.

 

[ChrisTanakaCanwell]

FWIW, my coworker's NT2 that he bought used in the late 90's died, and he sent it back for repair expecting a bill and they sent him a new NT2-A for free

 

[Sloan]

FWIW, my coworker's NT2 that he bought used in the late 90's died, and he sent it back for repair expecting a bill and they sent him a new NT2-A for free

BONAR!