Repair mic from microphone-parts for money?

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johnnywayne

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Hey, I bought a kit from microphone-parts to upgrade my 990.

I'm not a newbie to recording, but I am definitely a newbie soldering and building my own electronics. The kit was bought some time ago, there is much more info on the pages now and it looks even harder. I'm not sure the exact kit I bought is still there.

They were extremely helpful. I sent pictures in and they did what they could from pictures. They said the soldering looked ok and the mic did work, so I got some part right. The problem is that the gain is really low. Really low. I didn't replace the capsule yet, but that shouldn't affect the gain a whole lot, if anything it should be higher.

I have MS and since it was a while ago that I bought it, I can't hold a soldering iron anymore or do anymore work at all pretty much on it. I'd be surprised if I could screw it back together most days. So I need some help.

I don't believe it's not fixable since it at least passed signal last time I turned it on. I know what I would've checked next, had I been able to. I'm looking for someone to finish up this project for me, for pay of course. Most heavy lifting has been done it seems like, all the capacitors and what not are in place. I need someone to check my work and put on the capsule. I can send pictures and what they had to say as soon as yahoo lets me search again. Or not if you prefer to start from scratch.

Please help, I'm tired of seeing its poor body sitting with the other mics.

Anyone interested? Shoot me a price.


As an example, this has taken over an hour to peck out a letter at a tine.
 
Hi Johnny,
Sorry your project didn't work out.
Where about in the world are you?
 
Southern U.S, unfortunately, there's nothing much at all down here, certainly not a music shop that would work on something like this, if that's what you were thinking; Unless you want to give it a shot.

There is a massive "guitar shop" that's got everything. They're in an old mall (not sure y'all have those there, they're gross) and they have a different section in each old store in the mall. Like guitars in a huge store, amps in one, PA equipment and live sound in another, studio stuff in one and so on , but I've never seen anybody fixing anything. They might have that though.
 
I just saw a microphone sub-forum that I didn't when I was looking to post. I'm going to double post it over there in case they don't make it over here much.
 
No, don't. It's OK.

I'll move this thread into the DIY subforum for you.

---------- Update ----------

johnnywayne said:
Southern U.S, unfortunately, there's nothing much at all down here, certainly not a music shop that would work on something like this, if that's what you were thinking; Unless you want to give it a shot.

There is a massive "guitar shop" that's got everything. They're in an old mall (not sure y'all have those there, they're gross) and they have a different section in each old store in the mall. Like guitars in a huge store, amps in one, PA equipment and live sound in another, studio stuff in one and so on , but I've never seen anybody fixing anything. They might have that though.
Click to expand...

Nah, I was thinking there might be a member here, local to you, who could take a look at fixing it.
I'd be surprised if the guys at the guitar shop could change strings for you. ;) Steer clear.

In the mean time, can you point us to the kit that you bought?
If there's a before/after schematic that'd be great.

Maybe there's something simple that's gone wrong. A reversed capacitor or something?!
We have a good few guys here who'd be glad to take a look, I'm sure.

If possible, close and detailed pictures of your work would be great too.

Also, if you could quantify "really though" that'd be helpful.
It may be normal to see a gain reduction, depending on the mod.


You mention that the capsule still needs to be replaced. Is the new capsule a part of your upgrade kit?
It may be possible that the new circuitry mods aren't designed to work with the old capsule if it's a different type. Is that a possibility?
I'm clutching, but let me know what you think. :)
 
oh. I already tried, but it kicked me out so maybe you stopped me in time. Sorry.


It was something like this, same 990 that's everywhere: MXL 990 Circuit Mod Kit | PCB Replacement – Microphone-Parts.com
This is the main page for the 990 mods: MXL 990 Mods – Microphone-Parts.com

but it was a little different, there weren't new pcbs in the older ones, or headbaskets (though they should you how to do your own, sort of). Their site has grown immensely since the last time I was there. The 990 and just one or two more were all they had then. I have tests on it still I think. I might have deleted any before/after pics in a computer move, I see if I can take some of what I've got.

I did order a new capsule, but you by no means had to. So that couldn't be the cause. It was the first time I'd every soldered anything but that didn't seem to be the problem. Though there was a spot that didn't look too great to me, they (it was just one guy at the time) said it was fine. I didn't show them the final after shot though, and I there is a place that was iffy to me and I don't know if it could be the cause but it'll be easy to get a shot of.

be back with response curves fairly soon and pics a little later if they were deleted.
 
here's the email exchange (some of it), gonna be long-ish:



Microphone Parts
Oct 22, 2013

To

adam


(Hi Adam, I wrote this on the 15th in response to your first email, but somehow it never got sent. Sorry for the delay! Thanks for checking in again.)



Double-check the orientation of the diode at D3 and the electrolytic capacitors.

Visually inspect all the components, especially the capacitors under the board. Does anything look burned? Are any corners, especially of the film caps under the board, melted?

Measure the bias voltage by putting your meter into DC voltage mode. Put the negative lead on the chassis, or the mounting screw that holds the PCB to the chassis. Put the positive lead at the junction of D5/R12. What voltage do you read there? It should be at least 45, ideally around 60V.

Changing the capsule won't help. There's a problem with the circuit that needs to be fixed first.

Did you fully reassemble the mic before testing? If not, that's where the hum comes from. But it seems there's a sensitivity issue too.

--
matt.


On Tuesday, October 15, 2013 at 3:37 PM, adam wrote:

> Sorry to bother you again. I got finished and hooked it up. It works and signal is passing through but the sensitivity is really low, I had to turn up the gain on my interface all the way to get a small signal, which I think introduced noise, it could be the mic though. Do you have any idea what would cause it to work but just not have a hot or even medium signal level?
>
> I haven't changed the capsule yet, I didn't think that would make a difference for this, maybe (I hope) it does.
>
> Thanks again.
>
> -adam
>
>
>
> On Monday, October 14, 2013 1:41 PM, adam <adamwhopkins@yahoo.com (mailto:adamwhopkins@yahoo.com)> wrote:
> Yeah, I noticed they were already connected but didn't know if it mattered if the signal got to the next joint before it should (or if that's what would even happen). That makes me really happy, I'm ready to give it a shot. Thanks a lot, I really appreciate it. Fun project for my first foray into electronics and soldering, even if I screwed it up.
>
> -adam
>
>
>
> On Monday, October 14, 2013 11:46 AM, Microphone Parts <microphoneparts@gmail.com (mailto:microphoneparts@gmail.com)> wrote:
> Hi Adam,
>
> Those bridges are fine. If you compare your board to the "clean" image on page 24 of the manual, you'll see that the traces (the lighter green pathways) already connected the bridged joints. In other words, the two joints you connected with solder were already connected by copper traces inside the board.
>
> Your solder joints look pretty good. I don't see any signs of overheating, so that's a good thing. Some guys send me photos of boards that have been burned nearly black in spots.
>
> --
> matt.
>
>
> On Monday, October 14, 2013 at 8:51 AM, adam wrote:
>
> > Hi. I know it's not your job to answer questions about soldering or help us install your kits, but if you have the time I could use an answer to one question. I bought a 990 advanced mod from you last week and I've never soldered anything before. I could be wrong but I think I've done an ok job. I have two sets of two joints that are touching, I was wondering if these are ok? I cannot get the solder off of them to redo it. I imagine it matters it some places but I don't know anything. If you have the time, could you please look at these and tell me if you think it's ok to try to plug it in? They are circled in red.
> >
> > I really appreciate any help you can give me.
> >
> > -adam
> >
> >
> > Attachments:
> > - MicPCB.jpg
> >
 
johnnywayne said:
oh. I already tried, but it kicked me out so maybe you stopped me in time. Sorry.
Click to expand...

No problem at all. :)

johnnywayne said:
I did order a new capsule, but you by no means had to. So that couldn't be the cause. It was the first time I'd every soldered anything but that didn't seem to be the problem. Though there was a spot that didn't look too great to me, they (it was just one guy at the time) said it was fine. I didn't show them the final after shot though, and I there is a place that was iffy to me and I don't know if it could be the cause but it'll be easy to get a shot of.

be back with response curves fairly soon and pics a little later if they were deleted.
Click to expand...

Alright great, so the capsule is nothing to do with it. Was the original ever removed? Was it definitely refitted the right way?

I see where the chap said your bridged solder joints were inconsequential but if you have more up to date photos it'd be great to see them.
Were you able to read the bias voltage as he suggested? If at all possible, I'd do that.

I appreciate you may be limited in what you can do right now - I'm just throwing suggestions out there while we wait for others to come along. :)
 
I didn't have a volt meter at the time but I think I do now. This is the pic of the joints that he and I are talking about that was in my email, still looking on my computer. After his site has been redesigned and all these new products and guides, I believe they'd tell me these joints weren't good enough, but I'm going to go with his first answer since he figured all this stuff out himself and I could be wrong, it could still be just him.

Sorry if it's big here. I'm in a bit of a rush. Hopefully there will be more/ I can take more of the other side from all angles.
the circled were what i was asking about.


MicPCB.webp

and, the capsule was unsoldered but was left on the mic in the proper orientation. I would have to be a nitwit to have pics of what to do and mess that up. I've been known to be though. And while I don't fully understand the internals, it seems to me that it would a.)not work at all, b.) fry something, or c.)reverse the polarity, which would end up having the almost identical effect to what I'm describing.
 
Judging by the dates, I assume this is before and after sound at the same preamp gain. I didn't label it well because I was planning on not being looking back at it two years later. I also have some graphs but they were done in a program I lost in the computer transfer, coming after I reinstall it.
upload audio? I'll find a way to get it uploaded somewhere and link to it.

EDIT:
They are before and after. Same level, same distance from mic, nothing changed. I started a soundcloud account to see if I could get them here. They don't play for me, though they say they are ready, they may not be done uploading.

I listened to them for the first time since then and the second one mentions reversing polarity, but I don't know if it's talking about wiring the capsule itself backwards, or the capsule to the board. I'll check the instructions if I can find them. The only thing I'm positive I have is the new capsule.
There is no way I wired it to the board backwards, I was very careful to follow the pictures. Measure twice, cut once. I measured 10 times. Unless it's meaning that sometimes they need to be reversed for some reason, that's not it.
The second recording also mentions that even with the original capsule that the level should be hotter and there should be less self noise, I'm hearing the opposite.
Ok, done editing. Took me awhile to upload these files.

Forgot to say: the second recording is likely with the level turned all the way up. It's hard to remember the details of all this that long ago, especially with a disease that's eating my brain. The other was pretty high to begin with, I describe it at the end I believe. But that was close to normal, the input gain on that particular ADC seems to be pretty low. I would probably put the input at a 7 to 8.5 if I were forced to quantify, a pretty large swing but it doesn't matter since they were the same, but for the second test, I remembering it being so low that I had to turn it all the way up to get something audible. At one point, I removed the pop filter which I was using to limit my distance to the mic just to force more spl in. This may have even been that run. My opinion is that it is probably on ten or ten plus right on the mic.



 
Last edited:
Ok, this is all good stuff.
Do you happen to have a pic of the other side of the board?
That way we can gloss over capacitor orientation and stuff like that.

Thanks for all the detailed info. :)
 
adding some fresh pics. I can't get to those graphs so the only thing I would know to do without a major hassle, but still one probably not worth making, is to open those to .wavs in a daw or mastering program and either play them through and have the master fader record the highest level hit for a quick comparison. Throw that out the window if I tapped on the mic. Could just compare the waveforms, but like I mentioned, I now don't think the preamp level was the same by that point. I believe the post_mod to have been turned as far up as possible, so there's really nothing of interest in their relative output. I could do it again vs. a stock 990. Who has one but doesn't have two, if anyone, why? But this would just to be to gauge your question of how much is a lot. Just listening to those soundcloud files probably give a strong enough answer without knowing the dbs.

I lightened one to make it easier to see, I can do the other one if needed, or undo that one, whatever anyone needs. The configuration of wires and metal make it hard to shoot the couple of things (see, that's how much I know about what I attempted) that aren't in either pic but if they're needed, it won't be a problem to get my real camera out instead of the phone.

otherside2.webpOS_different_view.webpaudiotest.webpaudio_out.webp
 
Great stuff..Thanks again for the detailed info.

Are the transistor legs (q2) touching?
 
It's almost as impossible to tell holding it as it is from the pic. If there is a gap, it's less than .025cm. I guess that would be written in mm. Less than .2mm?
I'm trying. Trying to say it's about 1/100th of an inch, it's arbitrary what to call it this close, maybe the width of a hair.
It's very likely they are touching. Would that cause this problem?
 
johnnywayne said:
It's almost as impossible to tell holding it as it is from the pic. If there is a gap, it's less than .025cm. I guess that would be written in mm. Less than .2mm?
I'm trying. Trying to say it's about 1/100th of an inch, it's arbitrary what to call it this close, maybe the width of a hair.
It's very likely they are touching. Would that cause this problem?
Click to expand...

Absolutely.
As you say, it's not certain they're touching but if they are it could definitely cause your problem.

It looks like it might have gotten squashed down when you reassembled the mic so keep the transistor body where it is, and bend a little room between the legs.

Ideally you'd remove it, straighten the legs, and refit it much closer to the board, but I understand you may not be able to do that.
 
On a good day, I can type fairly well and I could probably solder one or two things, but I'm afraid now to take it off. I remember that piece (I think there were two capacitors and the FET with three legs) because it was such a pain. The legs went straight down, almost in a line, but they had to be bent like spider legs in order to fit and judging that was impossible. It was just a guess and then try again. You'd have to have a lot more experience than I to get it close to the pcb.

Thanks man, this is wonderful news, even if it doesn't fix it, that there are people with the same love for audio, recording, etc. that actually have knowledge in this area. I don't know why I didn't think of a forum earlier. I had pretty much resigned to throwing it away after it had set on desks and even in boxes outside the body (I hope that's not where it got bent and I'm just putting it back the way it was) until I ran across the capsule for the first time since I did this almost exactly two years ago and I couldn't throw it out, it's so close to a Neumann U47 capsule, they say. We'll see.

I'm going to have to reread this manual and get reacquainted with everything just to put it back together. I was meticulous in following their directions, and they were at giving them. They recommended this really expensive silver solder that I could only find in affordable quantities on ebay and I think I bought something like 2 feet, so I'll have to find that again before I change the capsule. I may be getting ahead of myself, but it's going to take a little while to get it back together.

Thanks again. I'll check back in as soon as I test it.

-jw

trans.webp
 
Hi again,
No problem. Glad to help, if it does help.
Like I say, that might not be the fault but it's certainly something worth looking at.
If it doesn't help, hopefully more people will have commented by the time you find out. :)

I wouldn't panic if you can't find the expensive solder. Ordinary stuff is going to do the job.

If it's a pain to get at just poke something between those two legs to separate them..Maybe poke something flat between them and turn it slightly, just to force them apart.
 
+1 for not bothering with the silver solder, not important. I too noticed the bent legs, but also that the legs are a real mess - solder very visible which makes me wonder if you accidentally overheated it. Normally you'd poke the legs through and the solder would only be on the other side, leaving the legs clean. They look like they've been in and out a few times.

I don't think this is really your fault, and not down to the MS. component level work on PCBs is not for beginners. You need a decent iron, a steady hand, and at my age (57) a magnifying glass in a little stand is absolutely essential to make a good job. The almost throwaway comment about cleaning the terminals shows that it's a bit misplaced, skills wise. If people can solder they don;t need to be told about cleaning, if they can't and need the cleaning tips, they've probably messed up anyway. You may need to source a new device if this one is physically mangled and possible heat damaged?
 
I wondered about the solder because I am always on the side of an inexpensive cable being just as good as a two hundred dollar one. If someone has better ears than I do, and they actually hear a difference, it's so slight that it doesn't matter to me. And these are basically really small cables.

I'm pretty sure that you're not actually seeing solder on that side of the board, maybe it's those 57 year old eyes :) . I think what you may be talking about are my many failed attempts to bend the legs to fit and so they're all crimped up with light bouncing of in various ways, like solder would do. That capacitor was the hardest piece I think, just because of all the bending and rebending. The leg that could barely reach the rightmost contact point wasn't the leg on the right, it was in the middle. So following those instructions didn't work for that. Hope I don't break it off trying to move the other one. I'll take a lot of pills beforehand so I don't shake too much.

Luckily I won't have to source any devices, I had two of these out of my mom's Portastudio thing. I've got plenty of mics. Just thought that if their claims were true, it wouldn't hurt to pay 200 bucks to turn a 60 dollar microphone into one with performance similar to venerable Neumanns. It's worth a shot if the final performance is equal to a mic costing the price or the kit plus the mic.
 
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