From: "Rich Peet" <>
> Just a couple heads up comments that is more than most want to read:
>
> Be sure to watch not just loud tones when using pairs but but also very
> quiet ones. They can occur anywhere and I watch them all the way to
> 40,000 cycles.
I saw this sort of thing when I was first experimenting with the mics
getting powering and such like sorted out. Since then no problems have
surfaced.
Most of the tone stuff is only detectable in sonograms, though the main
oscillation I ran into was audible.
> The current draw varies a lot from mic to mic so each time you change
> mics adjust your trim pot. This and wanting headroom above a single 9
> volt battery is why I went to full voltage regulation.
The several MKH-110's I have all end up very, very close, no messing
with the trim pot necessary.
I've not found headroom a issue, even with thunder.
> The coils are the second most valuable part of the mic. There is
> really few ways they can fail other than having to apply wax for core
> traction. Do your best not to screw with the leads from them as these
> are not available for replacement and if they were it would still be a
> nightmare.
The coils on the MKH-110-1 I opened looked fine, as did the rest of the
circuit. But the wires from the coils looked a little rough, like maybe
the insulating coating is deteriorating. I have the stuff for recoating
if it comes to that, just finished rewinding a stator for one of my
outboard motors. If I knew the specs for the coils I could wind new
ones. From past experience it's a very annoying job taking apart a coil
and counting turns. I'm certainly hoping I don't have to get into that.
The slugs in the coils were very loose. I'd say the test array must have
been exposed to strong sound.
> Before you call a capsule as failed, check the case to frame screw
> mounts for a good connection as they are different metals and that
> union does fail by corrosion.
This is especially true with this batch of MKH-110-1's. There is obvious
water marking and such like at the connector end. Some have corroded
housing screws.
> Don't worry so much about the scope when checking these mics. It will
> drive you nuts. Watch the current draw on the power supply lead.
I scoped the MKH-110's when I was first working on them. No problem
checking the oscillator that way as long as it's done in a quiet
environment. The scope is not much use checking the rest.
> To bad you do not wish to sell your doa's but I fully understand.
I view them as a opportunity to learn more about the mic. And, at worst
it looks like they would be a source of capsules even if the circuit
cannot be fixed. As I noted it would be nice to work out sensitivity
adjustment on the MKH-110-1's or they will only be good for limited use
in nature recording.
Walt
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