micolas
Well-known member
Did you manage to clean the pcb of dirt, residues, especially in the input area with high impedance?
Kookie's Blue Kiwi repair thread
- Thread starter SoundsOfJill
- Start date
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SoundsOfJill
Active member
Guess who's back?
It took me a while but I finally managed to find a hex wrench that fit, after having to order a set of micro screwdriver bits from Ali. For those wondering if you want to loosen the pot thumbwheel on a Blue Kiwi you'll need a .9 hex wrench, metric.
After successfully removing the directivity selector thumbwheel I was able to extract the PCB and inspect it fully and WOAH! The PCB was reaaaally dirty.
The person who tried to repair the mic before just went ahead swapped about half of the components on the board. How do I know? The solder joints are ugly, and covered in burnt flux. Among the seems that were swapped, it seems all caps, all large value resistors and all transistors were swapped. Also for some reason the wires running from the XLR connector to the board were also swapped. The extra mod seems to be that the traces to the capsule connector were scratched out and replaced by a blob of wire and solder. I guess for a similar reason that we use teflon posts on high impedence connections on other builds??
Before even thinking about cleaning I went and checked all the transistors on the board and none were dead. Then I started checking the caps. No weird stuff.Finally I started looking at the dirty solder joints and cross referencing with the PCB pics shared on the other Blue Kiwi post. Then as I kept inspecting each joint I saw something thin bridging a part where I think the polarizing voltage of the backplate was running through to.. ground. I tried to remove it but it was suck on good, maybe with flux. I managed to yank it off. I think it was body hair???Then I quickly reassembled the mic for a test aaaaaannnnd. The static is gone!!!!
So good news! I got a Blue Kiwi for super cheap!
But since the person who tried to repair it before replaced half of the components I have no idea if it sounds anywhere close to what it's supposed to. I don't even know if the fet is still biased correctly.
I'm gonna go back and clean the whole board though. I really don;t like what I saw there, and also I think I see some corrosion on some legs.
Also @Khron asked to share the name of the previous repairperson: It was Marc Henry L'Atelier du Microphone . I am a very inexperienced DIYer, so I might be wrong in the judgement of their handiwork, so I'll let you all decide by yourself from the pictures.
Thanks for reading!
It took me a while but I finally managed to find a hex wrench that fit, after having to order a set of micro screwdriver bits from Ali. For those wondering if you want to loosen the pot thumbwheel on a Blue Kiwi you'll need a .9 hex wrench, metric.
After successfully removing the directivity selector thumbwheel I was able to extract the PCB and inspect it fully and WOAH! The PCB was reaaaally dirty.
The person who tried to repair the mic before just went ahead swapped about half of the components on the board. How do I know? The solder joints are ugly, and covered in burnt flux. Among the seems that were swapped, it seems all caps, all large value resistors and all transistors were swapped. Also for some reason the wires running from the XLR connector to the board were also swapped. The extra mod seems to be that the traces to the capsule connector were scratched out and replaced by a blob of wire and solder. I guess for a similar reason that we use teflon posts on high impedence connections on other builds??
Before even thinking about cleaning I went and checked all the transistors on the board and none were dead. Then I started checking the caps. No weird stuff.Finally I started looking at the dirty solder joints and cross referencing with the PCB pics shared on the other Blue Kiwi post. Then as I kept inspecting each joint I saw something thin bridging a part where I think the polarizing voltage of the backplate was running through to.. ground. I tried to remove it but it was suck on good, maybe with flux. I managed to yank it off. I think it was body hair???Then I quickly reassembled the mic for a test aaaaaannnnd. The static is gone!!!!
So good news! I got a Blue Kiwi for super cheap!
But since the person who tried to repair it before replaced half of the components I have no idea if it sounds anywhere close to what it's supposed to. I don't even know if the fet is still biased correctly.
I'm gonna go back and clean the whole board though. I really don;t like what I saw there, and also I think I see some corrosion on some legs.
Also @Khron asked to share the name of the previous repairperson: It was Marc Henry L'Atelier du Microphone . I am a very inexperienced DIYer, so I might be wrong in the judgement of their handiwork, so I'll let you all decide by yourself from the pictures.
Thanks for reading!
One thing worth mentioning is, I wouldn't underestimate how sloppy some of Blue's circuit work could be. While they eventually moved to more standardized production, from what I've seen particularly of earlier Latvian stuff is they were somehow all over the place in terms of consistency. Of the (albeit limited) examples I've seen their work looks closer to competent DIY than major manufacturer production quality.
That said, it does appear quite a few components were swapped, likely without need.
That said, it does appear quite a few components were swapped, likely without need.
SoundsOfJill
Active member
I read through the repairman's website and through an interview he did. It appears to be what he does. People send him his microphones (mostly U87s it seems) for repair, and he says, the first thing he does is swap all the "crappy" components. Which seems a little counterintuitive to diagnosing a problem on a mic I guess. But it seems to work for him
Sounds a lot like what Michael Joly (of OktavaMod fame) used to do, back in the day...
Aesthetics of the board and/or workmanship aside, if a professional (?) couldn't manage to track down that (arguably) trivial of an issue.......
SoundsOfJill
Active member
I'm unsure if that was the original issue, or an unintentional "mod" from them.Aesthetics of the board and/or workmanship aside, if a professional (?) couldn't manage to track down that (arguably) trivial of an issue.......
It's not a handiwork. It's a hack job. Dirty and primitive (because a phrase: "pure and simple" would be wildly inapropriate).
Awful soldering. Unacceptable. As if done by someone with no experience at all.
At least two solder points look like they may be cold joints. Porous blobs.
Joints at the xlr and capsule connector are a model example of how not to break traces and solder.
There are special drills for breaking traces. Nothing fancy, just almost flat tipped drill bit.
If I were running an Microphone Atelier or even a mundane repair shop I'd splurge for one. Or have somebody to grind me one. Couple euros' expense. Serves for ages.
Those scratch marks... I have no words on my keyboard to express my disgust.
Small wonder no one got killed in the process. Well, on an afterthought... I can only assume...
I made a neater job first time cutting a trace with a dull screwdriver. Drunk. In the dark.
And let's not mention flux mountains. Because residue is not enough.
Awful soldering. Unacceptable. As if done by someone with no experience at all.
At least two solder points look like they may be cold joints. Porous blobs.
Joints at the xlr and capsule connector are a model example of how not to break traces and solder.
There are special drills for breaking traces. Nothing fancy, just almost flat tipped drill bit.
If I were running an Microphone Atelier or even a mundane repair shop I'd splurge for one. Or have somebody to grind me one. Couple euros' expense. Serves for ages.
Those scratch marks... I have no words on my keyboard to express my disgust.
Small wonder no one got killed in the process. Well, on an afterthought... I can only assume...
I made a neater job first time cutting a trace with a dull screwdriver. Drunk. In the dark.
And let's not mention flux mountains. Because residue is not enough.
micolas
Well-known member
Excellent. Congratulations!
Well, you'll have to post some sound tests (voice, acoustic guitar, etc.), possibly compared to a good stock microphone.
If the sound needs to be improved then you will make the necessary changes.
This is us, the DIY addicts.
SoundsOfJill
Active member
Oh yeah I spotted the cold joints. Did check them for continuity but I'm gonna go ahead and re-flow them. I wanted to take macro pics of the stuff tomorrow, before I clean things up. As I realize some of my pics were blurry.
micolas
Well-known member
SoundsOfJill
Active member
Agreed. I sent a message to the original owner warning them not to send anything for repair to that person anymoreThat doesn't make it any better / less worse
micolas
Well-known member
Well... the real professionals are found in GDIY.Aesthetics of the board and/or workmanship aside, if a professional (?) couldn't manage to track down that (arguably) trivial of an issue.......
Even big brands are keeping an eye on our activity, they are very attentive to our ideas, creativity, experiments and results
SoundsOfJill
Active member
Upon further inspection the "body hair" might have been a little metallic fiber from the headbasket assembly. They glued a decorative patch of mesh to the underside of it, above the PCB. I will show you pics tomorrow
SoundsOfJill
Active member
Erm.. so I went back today and took some 90% ethylic alcohol to the board to clean the flux with a cotton swab, and now the the noise is back and the signal is gone. Was that a bad idea? or did I not clean well enough and spread the flux everywhere? I'm kinda scared I screwed things up.
KrIVIUM2323
Well-known member
Hi,
Or it might be a cold solder joint. I would first clean thoroughly pcb from flux residue then redo the solder joint cleaning right after each point redone.
Have you spent more time cleaning on an area of the pcb? That could point to the culprit area.
Or it might be a cold solder joint. I would first clean thoroughly pcb from flux residue then redo the solder joint cleaning right after each point redone.
Have you spent more time cleaning on an area of the pcb? That could point to the culprit area.
SoundsOfJill
Active member
I'll do more of it. I had gone with a toothbrush at first, and when I inspected it just now it was completely stiff and reeked of rosin. I think there's just waaay too much flux on the board
micolas
Well-known member
We've all been through something like that.
It's a bad idea to use cotton, very fine filaments, wires, visible only with a strong magnifying glass, stuck to the pcb, components, soaked with various residues, which in the high impedance behave like high value resistors, enough to compromise the operation
Now you will have to scrub with a brush, with a lot of alcohol, whatever you use, wash repeatedly. I once cleaned a pcb for several hours, I used medical cotton wool. I ended up taking them with tweezers under a very strong magnifying glass, they were still there,hardly visible. I had to mount the microphone, test it, and then disassemble it and clean it again. All this many times.
It's a job for an old Chinese man
SoundsOfJill
Active member
Yaaayyyy, I'm excited!!!We've all been through something like that.
It's a bad idea to use cotton, very fine filaments, wires, visible only with a strong magnifying glass, stuck to the pcb, components, soaked with various residues, which in the high impedance behave like high value resistors, enough to compromise the operation
Now you will have to scrub with a brush, with a lot of alcohol, whatever you use, wash repeatedly. I once cleaned a pcb for several hours, I used medical cotton wool. I ended up taking them with tweezers under a very strong magnifying glass, they were still there,hardly visible. I had to mount the microphone, test it, and then disassemble it and clean it again. All this many times.
It's an old Chinese job
Oh well, that's how you learn I guess.
