Cleaning high impedance circuits in microphones

Hi,

Can anyone please give advice on what is the best method to clean the high impedance circuit of a condenser microphone?

I cant find this information nowhere, exept for some vague tips.....

Im interested in knowing from your experience, some solid information on what are the best chemicals and tools, both for cleaning flux and fingertip grease.

I have two moded microphones that have fingertip frease allover for shure, and exibit high low frewuency (brown) noise. I tried isopropyl alcool with q tips and things got a little better, but far from ideal.

Thanks

Thanks

Not sure where you want to cleanup, but if you are feeling brave, isopropyl with a toothbrush gets a lot of things done ...

But you can damage less robust things with this, so be extra careful.

We find Isopropyl works well, but be sure to get the kind with little water in it. 95 or 99%. If there is much flux
gentle scrubbing with a camel hair brush helps. Then soak it up with a qtip. Do this a couple times.

Another thing that helps is to fly input fet gates, bias resistors, and the like. In other works don't solder
the high impedance bits directly to the circuit board.

On our head amp products we sometimes use guard traces, which is highly effective.
Sensitive traces are surrounded by traces with the same signal, usually from a follower output.
With no electric field leakage current can't flow. Any leakage is dumped across the very low
impedance follower output thus little voltage is dropped. I realize you can't do this usually with a mod.

Les

Im not getting the results i whant with isopropyl. I used very pure one 98.8 lab tested if im not wrong.
Qtips leave fibers that i dont think helps in this case. And thay are filled with whiteners and all that stuff, i think maybe that also contaminates.

I've used a product called Flux Off for flux removal before.  We used it in a brush container to scrub off flux after doing soldering, and then used isopropyl alcohol in a spray bottle to flush the area and remove the of the flux off and remains of dissolved flux residue.  These boards weren't particularly high impedance though; piezo input circuits at the highest, but nothing like a condenser amp.

You might try a two step approach like that with some stronger solvent than alcohol to remove flux and grime, with alcohol used to clean the solvent and residue.

Maybe even need to go to a clean + conformal coat setup if you're really having issues with high impedance circuits and imurities getting in there.  Not something I've ever personally worked on.

nisios said:

Im not getting the results i whant with isopropyl. I used very pure one 98.8 lab tested if im not wrong.
Qtips leave fibers that i dont think helps in this case. And thay are filled with whiteners and all that stuff, i think maybe that also contaminates.

Click to expand...

I know I sound like a broken record for recommending this, but for cleaning electronics without leaving deposits, use Detergent 8 or other low-foaming, no phosphate detergent, diluted and rinsed with deionized water.

-a

You need to use A LOT of alcohol and rinse (in alcohol) several times.

Ideally scrub with a stiff bristle brush (& alcohol) and then 10 min. in an ultrasonic bath.  We did this at Calrec.

If you see any stains, after the alcohol dries, your alcohol is contaminated and you have to rinse again.

Beware of some solvents.  They may melt your polystyrene caps.

Cheap polystyrene caps can also trap muck that's carried into their construction by the alcohol.

Andy Peters said:

I know I sound like a broken record for recommending this, but for cleaning electronics without leaving deposits, use Detergent 8 or other low-foaming, no phosphate detergent, diluted and rinsed with deionized water.

-a

Click to expand...

I would love to try something like that, it makes perfect sense as grease from fingertips needs to be cleaned by emulsion. And alcool is not very good at that.

The only problem is that i cant find such detergent here. That seems to be one of those brands that you can only get in the US. But i will try to find something similat here.

ricardo said:

Ideally scrub with a stiff bristle brush (& alcohol) and then 10 min. in an ultrasonic bath.  We did this at Calrec.

Click to expand...

I never did an ultrasonic bath. Can you share some tips? You do it with isopropyl alcohol?

Thanks very much guys, interesting answers here.