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Author Topic: C414EB noisy filter switch  (Read 1779 times)

jackreynolds

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C414EB noisy filter switch
« on: December 08, 2016, 07:39:41 am »

Hi All,

I have a quick question regarding an unwell AKG C414EB (silver body) I have on my bench at the moment.

When I engage the filter switch it makes a nasty crackling noise, which makes me think one or both of the HPF caps may need replacing, or possibly a dry solder joint on one of the HPF resistors.

Has anyone come across this sort of problem before? The circuit boards are tiny and the components are very tightly packed, so I don't really want to start dismantling anything before I know where to look.

Thanks in advance for any info.

Regards

Jack Reynolds
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Jim Williams

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Re: C414EB noisy filter switch
« Reply #1 on: December 08, 2016, 11:12:57 am »

You have a dirty switch. Clean the contacts or replace it if that doesn't work.
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klaus

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Re: C414EB noisy filter switch
« Reply #2 on: December 08, 2016, 12:10:37 pm »

Agreed. I use Caig Pro Gold. That usually cures reoccurrence,, after the cleaning.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

gtoledo3

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Re: C414EB noisy filter switch
« Reply #3 on: December 08, 2016, 03:09:55 pm »

Hopefully not hi-jacking the thread - which one out of these, Klaus?:

http://store.caig.com/s.nl/sc.2/category.292/.f
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klaus

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Re: C414EB noisy filter switch
« Reply #4 on: December 08, 2016, 04:47:59 pm »

DeoxIT® Gold, #G100L-25C
(http://store.caig.com/s.nl/it.A/id.1568/.f?sc=2&category=292)

is what I use. I costed all of the Pro Gold products out, and found this format and quantity to be the most cost effective. But I believe the chemical formula for any of the Gold products is similar if not identical.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Jim Williams

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Re: C414EB noisy filter switch
« Reply #5 on: December 09, 2016, 11:33:15 am »

I always wash out any Caig products after use. The reason is it will attract more contaminants. Wash it out with a non-residue electronic contact cleaner or you will be back at it again.
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Kai

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Re: C414EB noisy filter switch
« Reply #6 on: December 09, 2016, 03:31:09 pm »

And the most important advice:
Do not directly spray the contact cleaner into the microphone or you will destroy it.
Usually I unsolder any switch or control that I clean by stuff like that and put it back after.
As this is not a good solution with the AKG 414 ( The switches are not easy to solder) the best way would be to completely remove the capsule first, then protect everything except the switch with tissue.
Spray some amount of the cleaner into a glass and apply from there little drops, using a tiny screwdriver or something like that.
If the switch is still in the microphone there is no sensefull way to wash it after this procedure, it has to stay like this. The only thing that you can do is trying to rub out some of the cleaner with pieces of paper. To my remembrance this is possible as the contacts are accessible from the outside.

Before all that I would test if the switch is really the source of the problem. Does it appear as soon as you touch or slightly move the switch?
 Or is it just the XLR connector?
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klaus

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Re: C414EB noisy filter switch
« Reply #7 on: December 09, 2016, 04:21:54 pm »

Hello Kai,
Because of your concerns, the product I recommended avoids the issue. It is not a spray, but an small flask with a 2" needle applicator, not unlike a syringe, which helps to precision-target the oily fluid to the appropriate spots without spillage.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Kai

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Re: C414EB noisy filter switch
« Reply #8 on: December 10, 2016, 11:18:49 am »

...the product I recommended avoids the issue. It is not a spray...
Important that you mentioned this fact.
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gtoledo3

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Re: C414EB noisy filter switch
« Reply #9 on: December 10, 2016, 12:44:27 pm »

Worth mentioning; every once in a blue moon, simply exercising the switch, knob, whatever, will wind up cleaning up the problem.

In this case, it might be worth carefully moving the switch back and forth a dozen or so times, with the mic unplugged.
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jackreynolds

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Re: C414EB noisy filter switch
« Reply #10 on: December 15, 2016, 02:49:43 pm »

Great. Thanks for the advice.

I have applied a tiny amount of deoxit gold (from a small plastic tube/vial)to just the contacts of the switch, so hopefully that will fix it.

I'm not sure how to clean away any residue, but perhaps an isopropyl alcohol swab?

I shall report back when I have had a chance to test it out,

Cheers

Jack
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klaus

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Re: C414EB noisy filter switch
« Reply #11 on: December 15, 2016, 02:55:08 pm »

The alcohol will remove and neutralize the deoxidizer you just applied. Better to just mechanically wipe the excess off.
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Klaus Heyne
German Masterworks®
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jackreynolds

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Re: C414EB noisy filter switch
« Reply #12 on: December 20, 2016, 12:37:00 pm »

Just to update - my cleaning attempt does not appear to have fixed the problem.

I used some Kontakt60 and exercised the switch, followed by a tiny drop of Kontakt Gold - but the problem persists - a rumbling crackling sound.

I have therefore removed the capsule and isolated the switch enough to give it more of a wash with contact cleaner (having masked off the rest of the components)

Hopefully this will flush out whatever is stuck between the contacts, I have a feeling it some flakes of red paint which may have originally been securing screws in place as there is some evidence of this floating around elswhere inside the mic.

I will report back again shortly.

Jack
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klaus

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Re: C414EB noisy filter switch
« Reply #13 on: December 20, 2016, 12:50:43 pm »

If the rumble remains with the capsule removed, it is a switch contact issue, most likely. If the rumble is gone without the capsule, the static / discharge sounds could stem from a contaminated capsule. If so, do not clean with mechanical means (brush, etc.)
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

jackreynolds

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Re: C414EB noisy filter switch
« Reply #14 on: December 20, 2016, 01:24:16 pm »

Don't worry, I won't be touching the capsule!

The noise only appears when the 75Hz or 150Hz positions are selected on the filter switch. All the other settings ie the pad and pattern switches work perfectly, and the noise sets in a second or so after engaging the filter switch, which makes me think it could be a capacitor charging up and then leaking.

Having carefully removed the capsule and masked off the rest of the mic, I flushed the switch through with Kontakt 60, then wiped away any residue with sheets of paper as you suggested, then applied a tiny amount of Kontakt Gold to the gold contacts - which actually look very shiny and clean - and then again wiped away any residue.

Upon re-assembling and testing the mic, the same problem persists, so I'm not sure what the next move should be at this point.

Thanks for all your help so far. I am now familiar with dismantling a 414EB! I love the slide-in capsule mount and push fit electrodes for the capsule.

Cheers

Jack
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