|
Hi together
I recently purchased a Rode NT1-a from a thrift store with a “No Tone” sticker on it.
If I connect it to the audio interface and activate phantom power it doesn't work.
Miraculously, after three minutes of warm-up time, the gain meters start and the NT1-a seems to be working perfectly. The sound is crisp and clear. No noise can be heard either.
I opened the mic body. The circuit board and the caps look clean. The only thing I have noticed so far is that there is some dirt and dust on the capsule diaphragm.
Does anyone have an idea what might be wrong? Should I replace the capsule?
Many thanks!
Heinz
?
|
.
?
Take DC voltage measurements on the pc board, right when it first powers up and is dead, and again when the mic finally works.
?
My first rough guess is that the voltage multiplier circuit that creates the capsule bias voltage doesn't start oscillating right away. You can check the oscillator with an oscilloscope.
?
?
|
Am 22.10.24 um 15:11 schrieb Heinz via groups.io: ...the NT1-a seems to be working perfectly. The sound is crisp and
clear. 'Crisp' certainly is one way to describe it. :-) Interesting part starting at 3:55 Ralf -- Ralf R. Radermacher - K?ln/Cologne, Germany Blog : Audio : Fotos :
|
The only thing I have noticed so far is that there is some dirt and
dust on the capsule diaphragm. Does anyone have an idea what might
be wrong? Should I replace the capsule? It is very unlikely that capsule contamination causes the delayed warm-up time you describe. If the capsule were at fault, the mic would not start working later; the problem would be permanent. Edge-terminated capsules such as the one in the NT1-A are more susceptible to moisture damage than are center-terminated capsules, in my experience, but this would not manifest as a delay until signal is passed. Replacing the capsule would change the mic’s frequency response. That is a popular upgrade; you’d likely want to choose a capsule whose response does not require corrective high-frequency attenuation. But again it would not fix the circuit problem. PSA: attempts to clean a large-diaphragm capsule usually result in stripping the gold from the diaphragm. This ends the capsule’s service life. Gold adheres poorly to Mylar, and definitely will not withstand a cotton swab and solvent. — matt.
|
On Wed, Oct 23, 2024 at 12:06 AM, recordinghacks wrote:
It is very unlikely that capsule contamination causes the delayed warm-up time you describe. If the capsule were at fault, the mic would not start working later; the problem would be permanent.
Edge-terminated capsules such as the one in the NT1-A are more susceptible to moisture damage than are center-terminated capsules, in my experience, but this would not manifest as a delay until signal is passed.
Replacing the capsule would change the mic’s frequency response. That is a popular upgrade; you’d likely want to choose a capsule whose response does not require corrective high-frequency attenuation. But again it would not fix the circuit problem.
PSA: attempts to clean a large-diaphragm capsule usually result in stripping the gold from the diaphragm. This ends the capsule’s service life. Gold adheres poorly to Mylar, and definitely will not withstand a cotton swab and solvent.
?
Hi Matt. Many thanks for your inputs. I will test the NT1-a for same time. Usually the recordings I do are several hours long. If the NT1-a works reliably after a three minute warm-up period, it might still be OK to use it as a (low cost) drop rig mic in the field. I will not try to clean the capsule surface. The popular capsule upgrade you mentioned sounds much more interesting. I will certainly do some research on this topic.
?
@Ralf
I had to *LoL* when I saw the video at minute 3:55. ?The mic seems to be famous for its crisp reproduction properties. :-) Anyway. The NT1-a caught my attention when I listened to the recordings of . A field recordist from Island . To my ears his NT1-a NOS setup sounds really nice.
?
I would like to experiment with the NT1-a as a third (MID) mic in a SimpleP48 Jecklin disc (OSS) setup I'm currently building.
?
@kennjava
I hardly resist when I discover interesting microphones in junk boxes of reuse stores or at flea markets. I usually try to give them a second life or at least learn something about their design characteristics. Sometimes I get lucky and the mic's that I find aren't broken at all. Other times, only a simple repair is necessary or the installation of a battery in the hidden battery compartment. Regarding the NT1-a I will do some measurements. Unfortunately, I don't have an oscilloscope.?
?
Many thanks!
?
Heinz
Btw: The night ambiance recording has been recorded with a pair of SimpleP48 attached to a tree. In case somebody is interested.
|
A short update.
I tried a continuous test recording near the house for several hours today.
After 3 minutes, the recording continued for about an hour. Then the recording was paused for about 6 minutes and it continued recording again.
Every now and then there were interruptions.
It looks like it's dying.
|
On Tue, Oct 22, 2024 at 08:06 AM, recordinghacks wrote:
It is very unlikely that capsule contamination causes the delayed warm-up time you describe. If the capsule were at fault, the mic would not start working later; the problem would be permanent.
Edge-terminated capsules such as the one in the NT1-A are more susceptible to moisture damage than are center-terminated capsules, in my experience, but this would not manifest as a delay until signal is passed.
...but sometimes capsules can cut in and out due to humidity causing a short on the capsule, no? Maybe not in the pattern we're seeing in this particular case, but just spitballing... I had a CAD E-350 that would stop working after you talked into it for a while because the humidity of the breath would combine with crap on the capsule and cause it to fail. Then after some time it would come back in. After a capsule cleaning it worked fine. (Probably this board helped me figure this out, can't recall now.) It just makes me wonder if the dirty capsule might be reacting to changes in temperature/humidity. Might be a dumb long shot, but maybe Heinz should post pics of the capsule just to sanity check the situation?
?
|
On Thu, Oct 24, 2024 at 01:50 AM, Casey wrote:
It just makes me wonder if the dirty capsule might be reacting to changes in temperature/humidity. Might be a dumb long shot, but maybe Heinz should post pics of the capsule just to sanity check the situation?
High humidity is a real problem here. I usually store microphones in dry boxes. Especially during the hot and humid summer season. The NT1-a seems to be particularly susceptible to moisture.
?
Here are the capsule photos you requested. I added two photos from the circuit board as well.
It doesn't look very promising. I wonder what the other side of the capsule might look like, but I was afraid to take the back plate off. I guess Casey is not entirely wrong in the estimate. It could well be moisture damage.
 ---  Btw: Yesterday I registered the microphone with Rode. They promptly issued an extended warranty for the product until 2034. Maybe I'll send it in and ask for a cost estimate for a repair. Considering that the NT1-a came out in 1995, there may still be an additional defect in the circuit.
?
I'm aware this is a Micbuilder and maybe not a Micrepairer group, so I really appreciate your responses.
?
Perhaps one final question about cleaning large diaphragm capsules. I found many contradictory statements on the Internet. Is there a way to clean a capsule without kicking it in the bucket?! I saw that looked trustworthy and somehow made sense to me. Have any of you tried this method or perhaps know a more reliable way? I'm just wondering.
?
Many thanks!
?
Heinz
?
?
?
?
|
Here are the capsule photos you requested. I added two photos from the circuit board as well. From the images posted the capsule doesn't look too bad, honestly, i.e. pretty normal for an older/used mic I'd say, but I'm not an expert. (Of course you can't tell for sure from a visual inspection whether there would be issues.) In terms of DIY cleaning, I read enough about the process to be scared to attempt it myself with a mic I cared about. I started to try but ended up sending it away. That video seems way more aggressive than I would ever dare be, but I'm no expert and will let others more knowledgeable weigh in. And of course this could be a good practice mic for your technique, so there's that. But I wouldn't bother heading down that road until/unless an expert here agrees that it's a potential explanation for your symptoms. Btw: Yesterday I registered the microphone with Rode. They promptly issued an extended warranty for the product until 2034. Maybe I'll send it in and ask for a cost estimate for a repair. Heck yeah -- especially if it's under warranty that would definitely be the way to go. :-) -c
|
On Wed, Oct 23, 2024 at 09:09 PM, Heinz wrote:
Is there a way to clean a capsule without kicking it in the bucket?!
I've tried - the finest small soft artist's brush, distilled water, the slightest touch with wet bristles near parallel to the diaphragm -? the answer, for most of us mortals, is... no. Gold comes off. And from your photos, the capsule doesn't look that bad for its age, nor do I think it's the capsule that would cause the problem you're observing.
?
While the mic is open, connect it to your recorder or mixer, and gently tap the board and connections with the the back of a plastic pen while listening (at safe levels!) , to see if there's something loose.
|
Heinz, can you take a picture that zooms in on the high-Z area around the red wire? The picture becomes too blurry to see all the details when zooming in, but it looks like there has been some soldering going on there. And it looks like there are charred remanents of damaged conformal coating and flux residues. These can become conductive and short out the signal. The coating is there for a good reason and should be intact! Rode uses a high polarization voltage of 100V or more. Good for SNR, but it increases moisture sensitivity and accelerates tracking and dendrite growth.
?
Carefully remove discolored coating and flux, then clean with IPA and a brush. Finally, rinse off with abundantly applied IPA. I use an IPA aerosol can for that. Dry with hot air and apply new conformal coating. I'm not sure, but I think it's acrylic coating they used. Epoxy could be used as well, but may be harder to remove in case you have to solder on new wires of a new capsule.
?
Good luck with it!
?
Jan
|
On Thu, Oct 24, 2024 at 12:29 PM, kennjava wrote:
While the mic is open, connect it to your recorder or mixer, and gently tap the board and connections with the the back of a plastic pen while listening
I tried your suggestion. But as soon as I remove the cover, connect the XLR cable and switch on the phantom power, the mic is caught in a ground loop. Or is it because the EMI/RFI shield is missing? I recorded a bit... 
?
I gently tapped the board and connections with the back of a plastic pen while listening. The only thing I could hear was the humming. Even when I snapped my fingers directly in front of the capsule after 5 minutes, the level indicator didn't change.
?
|
On Thu, Oct 24, 2024 at 02:55 PM, @jp8 wrote:
can you take a picture that zooms in on the high-Z area around the red wire?
Many thanks for pointing me to the area and the detailed instructions to clean it up!
?
?
I will give it a try to remove the discolored coating and flux. It will take some time because I have to order the acrylic coating first. Any tips on which coating I should use?
?
Rode uses a high polarization voltage of 100V or more?! That's interesting. I have a beginner question. Is polarization performed every time the microphone is switched on or every time phantom power is applied respectively? Without polarization the capsule doesn't work, right? What could be the reason that polarization takes time? Shouldn't the polarization be kept? I'm asking because I noticed a different behavior today.
If I don't use the microphone for several hours and then turn it on, the NT1-A needs 3 minutes to warm up before it starts working. If I then unplug the XLR cable and plug it back in after three minutes, no warm-up phase is necessary. The NT1-a is immediately ready for use. Apart from the fact that after a longer period of operation, there will be interruptions again. Which could indicate a problem between the capsule and the circuit board?! I'm just guessing. Many thanks, Jan!
?
?
?
|
You will get emi and hum without the headbasket — it is a faraday cage? Best Regards,
Jules Ryckebusch?
toggle quoted message
Show quoted text
On Oct 24, 2024, at 06:34, Heinz via groups.io <heinz.hartfiel@...> wrote:
? On Thu, Oct 24, 2024 at 12:29 PM, kennjava wrote:
While the mic is open, connect it to your recorder or mixer, and gently tap the board and connections with the the back of a plastic pen while listening
I tried your suggestion. But as soon as I remove the cover, connect the XLR cable and switch on the phantom power, the mic is caught in a ground loop. Or is it because the EMI/RFI shield is missing? I recorded a bit... <inline.0.part>
?
I gently tapped the board and connections with the back of a plastic pen while listening. The only thing I could hear was the humming. Even when I snapped my fingers directly in front of the capsule after 5 minutes, the level indicator didn't change.
?
|
Clean the flux and debris off with isopropyl alcohol the ?test. ?If you want to reseal it you can use clear nail polish. ?
Next question: phantom power is used to generate the internal voltage used by the mic electronics and a bias generator. The bias generator creates the capsule bias voltage which is usually 60VDC ?in run my mics at 80V ?rode goes higher. It is only present when the mic is powered on. That voltage charges the mic capsule, which is a capacitor or “condenser” in 1930’s speak. When sound vibrates the gold plated diaphragm the capacitance changes and that results in a vintage change in the capsule. Which is what we want.? Best Regards,
Jules Ryckebusch?
toggle quoted message
Show quoted text
On Oct 24, 2024, at 07:48, Heinz via groups.io <heinz.hartfiel@...> wrote:
? On Thu, Oct 24, 2024 at 02:55 PM, @jp8 wrote:
can you take a picture that zooms in on the high-Z area around the red wire?
Many thanks for pointing me to the area and the detailed instructions to clean it up!
?
?
I will give it a try to remove the discolored coating and flux. It will take some time because I have to order the acrylic coating first. Any tips on which coating I should use?
?
Rode uses a high polarization voltage of 100V or more?! That's interesting. I have a beginner question. Is polarization performed every time the microphone is switched on or every time phantom power is applied respectively? Without polarization the capsule doesn't work, right? What could be the reason that polarization takes time? Shouldn't the polarization be kept? I'm asking because I noticed a different behavior today.
If I don't use the microphone for several hours and then turn it on, the NT1-A needs 3 minutes to warm up before it starts working. If I then unplug the XLR cable and plug it back in after three minutes, no warm-up phase is necessary. The NT1-a is immediately ready for use. Apart from the fact that after a longer period of operation, there will be interruptions again. Which could indicate a problem between the capsule and the circuit board?! I'm just guessing. Many thanks, Jan!
?
?
?
|
On Thu, Oct 24, 2024 at 10:18 PM, Jules Ryckebusch wrote:
Clean the flux and debris off with isopropyl alcohol the ?test. ?If you want to reseal it you can use clear nail polish. ?
?
Next question: phantom power is used to generate the internal voltage used by the mic electronics and a bias generator. The bias generator creates the capsule bias voltage which is usually 60VDC ?in run my mics at 80V ?rode goes higher. It is only present when the mic is powered on. That voltage charges the mic capsule, which is a capacitor or “condenser” in 1930’s speak. When sound vibrates the gold plated diaphragm the capacitance changes and that results in a vintage change in the capsule. Which is what we want.?
?
?
I will clean the flux and debris off tomorrow.
Many thanks for the explanation, Jules. That would explain the newly discovered behavior.?
?
|
On Thu, Oct 24, 2024 at 10:18 PM, Jules Ryckebusch wrote:
Clean the flux and debris off with isopropyl alcohol the ?test.
?
Hi Jules. I've put on my magnifying ocular and cleaned the flux, debris and the burned coating. When I looked more closely with the magnifying ocular, I also noticed a kind of greasy film all over the circuit board. I cleaned this too and dried it with paper towels that I normally use to clean lenses.
?
When I turned the mic on, it worked! I'm going to do a test recording now and let it record for a couple of hours. I will inform you of the results.
?
@JP8 (Jan)
Thanks again for the tip. Hopefully I've learned my lesson and will check any used microphones I buy more carefully before turning them on or bothering you guys when something is wrong. The NT1-a seems to be from March 2018. If it doesn't work as expected, I'll send it in.
?
?
I will buy nail polish soon and use it as a coating.
?
Many thanks!
|
Happy to help, no problem! Nice to hear it seems the mic is working properly now!?
?
Enjoy your purchase.
?
Jan
|
I've tried - the finest small soft artist's brush, distilled water, the slightest touch with wet bristles near parallel to the diaphragm -? the answer, for most of us mortals, is... no. Gold comes off. And from your photos, the capsule doesn't look that bad for its age, nor do I think it's the capsule that would cause the problem you're observing.
I would use a blower brush (for camera lenses) and VERY GENTLY remove any loose stuff.? I would NOT USE ANY LIQUID or ANY HIGH PRESSURE AIR.
?
Yes, you might remove some Gold but actually the capsule will work fine with a bit of Gold missing :)? The real danger is your liquid moving yuck behind the diaphragm.? Then the mike will be forever / intermittently noisy. :(
?
I think Josephson or one of the other commercial mike makers said you DON'T TRY CLEANING CAPSULES UNLESS YOU CAN REPLACE THE CAPSULE IF IT ALL GOES TO SHIT.? I second this as an ex commercial mike maker.
?
From your description, I don't think you have a dirty capsule.? This would be VERY NOISY long before it stops working.
?
I think the muck on your PCB coupled with humidity, was making the polarizing voltage generator wonky.? After 3 min. the warmth of the electronics dried the stuff enough for it to work again.? The polarizing voltage has some serious decoupling to remove any noise in the generator.
?
In da 80s, I didn't like ANY of the conformal coatings for the HiZ part of any PCB.? Modern stuff might be OK but I have no experience.
|
In da 80s, I didn't like ANY of the conformal coatings for the HiZ part of any PCB.? Modern stuff might be OK but I have no experience. Supposedly you can solder through this stuff: ...I got some for a project but didn't actually end up using it (for other reasons). -c
|
