Topic: How to clean up this M7 capsule (Read 7415 times)

Oleh Malyy · « **on:** November 19, 2011, 05:25:48 am »

I would appreciate advices how to clean up this M7 capsule

and

klaus · « **Reply #1 on:** November 20, 2011, 01:34:20 am »

Your question implies that you are inexperienced in cleaning capsules. The chance that you will ruin the capsule if you were to try it is close to 100%.

What you should therefore NOT do: use a brush to remove the hard debris or use water (let alone alcohol) on the diaphragms. While PVC (my assumption that this older Gefell M7 capsule you are showing does not have Polyester membranes) is not hygroscopic, it is very hard to remove any type of cleaning moisture from the cracks that weather-checking in the gold deposits form.

A long way to tell you that removing contamination from this neglected capsule is not a job for a lay person, internet advice to the contrary be damned.
(I could go into the pitfalls of the interwebs as the almighty remedy for all that ails us, but maybe another time.)

Oleh Malyy · « **Reply #2 on:** November 20, 2011, 04:45:52 am »

you are right - I have not such experiences.

And, yes, this is an M7 capsule from a Neumann/Gefell UM57 microphone

klaus · « **Reply #3 on:** November 20, 2011, 02:40:13 pm »

One more thought about the delicate cleaning of sophisticated condenser mic capsules:

Servicing capsules is not a growth market that would attract new apprentices to the field, because there is more profit in either re-skinning or replacing a capsule, regardless of whether that would be appropriate in all cases. Therefore, the few people who have experience with restoring capsule surfaces probably not grow much. Hence the understandable desire of microphone owners to try to do it yourself. Hence the increasing number of capsules I see now whose surfaces have been damaged after amateurish cleaning attempts.

soapfoot · « **Reply #4 on:** November 20, 2011, 11:34:57 pm »

Klaus, do you utilize ultrasonic cleaning technology when cleaning capsules?

Tim Campbell · « **Reply #5 on:** November 21, 2011, 02:06:11 am »

I agree with Klaus. In the last few years a large number of the capsules sent to me for re-membraning show obvious signs of amateurish attempts at cleaning. Most show a large loss of gold from the surfaces or worse, actual perforations.

Jim, the cleaning of each membrane is different based on it's condition. The least amount of cleaning necessary is always best.

Klaus, the time required to clean a capsule is much less than that necessary for re-membraning so the profit margin should be the same.

Oleh Malyy · « **Reply #6 on:** November 21, 2011, 02:13:23 am »

Please PM me (or email direct: olehmalyy(att)gmail(dot)com) your offer (price, terms etc.) for cleaning this capsule.
Who can do that and have such experiences.

Kai · « **Reply #7 on:** November 21, 2011, 09:43:26 am »

Quote from: klaus on November 20, 2011, 02:40:13 pm

Therefore, the few people who have experience with restoring capsule surfaces probably not grow much.

Just by curiousity, not that I want to try that by myself:
what are the basic techniques for cleaning?

I don't ask you to tell us your business secrets, just the basics.

Regards
Kai

klaus · « **Reply #8 on:** November 21, 2011, 01:00:38 pm »

Chemically, ultrasonically, mechanically. Not always all three, and not always in that order.
Examples of deviation: ultrasonic on very thin metal membranes is detrimental to the membrane's pre-tension. Likewise, ultrasonic cleaning can dislodge fine particles between the backplate and its membrane. Likewise, mechanical removal before other methods on a capsule as shown here would severely scratch the gold deposit.

I also choose my chemicals carefull-after having destroyed a few of my customers' capsules and having to replace them with precious vintage ones from my stash- but that is really the only method to get better in this esoteric field: you can make some assumptions from the materials you are dealing with, but in the end, a few catastrophic mishaps along the way are the only way forward!

There was a thread in my old forum about this subject, as well as an extensive "sticky" in my "Sticky" forum. Read more there.

gkippola · « **Reply #9 on:** November 23, 2011, 09:21:45 am »

I have a few AKG CK1 caps that I don't want to pay a bunch to have cleaned----is Trichloroethane a suitable solvent for removing polar stuff from these diaphragms, assuming one has good work environment for doing so?

Tim Campbell · « **Reply #10 on:** November 24, 2011, 01:38:02 am »

Do you mean methyl chloroform or vinyl trichloride?
I wouldn't allow either of them anywhere close to a membrane. The metal is deposited on the PET film by evaporation, there is no other method used for binding it.
Even using isopropyl alcohol with any undue pressure will completely remove the gold. Remember what it is you're trying to remove - mostly spit,sweat, nicotine and dust-
all fairly soluble in water. Any other chemicals should be used in a very diluted form.

kats · « **Reply #11 on:** November 24, 2011, 08:49:22 am »

What other issue can cause one side of a capsule to have no output assuming the rest of the mic electronics are as they should be?

I have a k47 with this problem, the capsule had been reversed years ago - probably for this reason. I ordered a new K47 from Neumann resigned to the fact that the original will probably need a less than desirable re-skin. With at in mind, I figured there's only one way to learn how to clean a capsule and "went for it". I think I did a decent job, and it seems like I never caused any damage. The front side sounds exactly as it did before (lacking in bass) and the back side still doesn't output signal.

Besides dirt getting in between the membrane and backplate (which surface cleaning will not help) what else could cause a capsule to "just stop"?

Tim Campbell · « **Reply #12 on:** November 24, 2011, 11:43:23 am »

Tony, like all other electronics, if you hear hum most likely a broken or open connection . If you hear silence probably a shorted connection.

klaus · « **Reply #13 on:** November 24, 2011, 09:25:21 pm »

Why not start with the most obvious measurement of any capacitor, including one that is used as a microphone capsule?
Measure the capacitance between backplate and the front diaphragm. Then measure between rear diaphragm and backplate. There should not be a greater difference between the two measurements than ca. 10pf.

Tim Campbell · « **Reply #14 on:** November 25, 2011, 01:32:09 am »

Although capacitance can tell you a lot, most people don't have capacitance meters that can read accurately within the 40-90 pf range. I've had customers give me capacitance readings from capsules that turned out to be more than 20pf wrong because they measured with a standard multimeter.

gkippola · « **Reply #15 on:** November 26, 2011, 05:21:16 pm »

Alcohol, water, should never be used for cleaning diaphragms. Trichloroethane is a non-polar solvent that has been used for decades as a cleaner for sensitive electronics, removes organics, water, oils, grease-- Anyone here have experience with it for mic capsule component cleaning?

Tim Campbell · « **Reply #16 on:** November 26, 2011, 08:00:09 pm »

Do you mean methyl chloroform or vinyl trichloride? Trichloroethane is a name used for both of these substances.
Demineralized water is THE most used liquid for cleaning capsules. Most of the debris deposited on membranes arrives there suspended in one form of water or another and unlike the gold that you don't want to remove is water soluable.

gkippola · « **Reply #17 on:** November 27, 2011, 03:15:00 pm »

I have seen gold fall off with the use of water. 1,1,1,TCE is a proven solvent for fragile electronics and many types of film, and film plastics. Very delicate stuff. There are new solvents vying for the replacement of TCE, because it has been discontinued because of ozone depletion restrictions. Can't blv there isn't a better understanding of this stuff, it is very frustrating. Those in the know won't speak.

klaus · « **Reply #18 on:** November 27, 2011, 06:25:35 pm »

You responded quite strongly to one person's negative opinion of this solvent. I have used it for many years, and quite successfully, in the course of capsule cleaning.

But the looming issue of ozone depletion is one that needs to be investigated further. For example, can 111 TCE be properly re-used, cleaned, and in the end recycled? What is the absolute harm to our ozone layer of this chemical in comparison to say, ozone depleting chemicals used in air conditioning?

The one feature that is so attractive about 111TCE is also the one feature that now causes environmental headaches: its volatility.

Tim Campbell · « **Reply #19 on:** November 28, 2011, 09:47:37 am »

Water in and of itself cannot remove gold from a membrane. You may have seen gold flake off a membrane with water on it when abrasion from a brush or other utensil was applied. I'm sure the rubbing removed any poorly adhered gold and not the water.

gkippola, you mentioned wanting to clean CK1 capsules. These membranes are only held in place by glue at the edge of the membrane. Since one of the described uses for trichloroethane is dissolving glue it might not be the best choice. It's other descibed use is as a degreaser. You won't find much grease or oil on a capsule membrane unless someone has been touching it with their fingers.

If Klaus says this compound is useful for cleaning capsules I accept that as fact.

In my more than 10 years experience cleaning capsules I have found that the mildest agents and least abrasion necessary to clean the capsule the better. As David Josephson has stated before, if you can't afford to lose the membrane or aren't capable of repairing it if it gets damaged you shouldn't try cleaning it.

gkippola · « **Reply #20 on:** November 29, 2011, 01:00:12 pm »

Thanks much for the reply Klaus- indeed it would be beneficial to be able to recycle TCE, precisely that is being done with other solvents which have been used as replacements. Being that TCE is non-polar, a simple test of conductivity might provide at least a ballpark indication of it's contamination. A method for the evaluation of the dissolved contaminants, and a method for removing them from the solvent--a redistillation probably- but in a strictly controlled industrial environment.I would be interested in knowing what materials to stay away from with TCE.
And Tim, one of the attributes of this solvent is that it evaporates quickly w/o a trace. Glues can remain unaffected by the quick action, unless you want to do an immersion in an ultrasonic bath, and knowing what the reactivity might be can alleviate issues. I have had factory CK1, and B&K diaphragms come loose just thru normal use and contamination-

panman · « **Reply #21 on:** November 29, 2011, 04:51:20 pm »

Quote from: gkippola on November 29, 2011, 01:00:12 pm

I would be interested in knowing what materials to stay away from with TCE.

Ha, that thread made me lough. Memories of my mother removing chewing gum from my hair with TCE come to my mind from the childhood. So that certainly is one

.

klaus · « **Reply #22 on:** November 29, 2011, 05:27:25 pm »

...and I should apologize if anyone reading this thread is coming away from it not much smarter than before:

There are proprietary issues involved in the proper process of cleaning a capsule to a professional level. Some of these processes and issues have been acquired by practitioners over decades of hard work and countless screw-ups. That investment needs to be recouped, rather than given away.

gkippola · « **Reply #23 on:** November 30, 2011, 10:28:34 pm »

I send my favorite mics out for proper cleaning, probably always will. I think most do/would do the same. But the budget does not provide for all of them to get a proper job, I have way too many. I think there are a more than just a few who are in the same boat. There's ample food for discussion on this topic, hopefully it can pick up somewhere. There's a demand for a better understanding of the upkeep of the mic toolbox,

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Author Topic: How to clean up this M7 capsule (Read 7415 times)