Tuesday, September 6, 2016

Fixing the Heil BM-10

Repaired Heil BM-10
Back in the early 1990s, I'd been contesting using a Kenwood MC-50 desktop microphone. It worked well enough. But long hours of contesting in one position became uncomfortable. So, I decided I need a headset with a boom mic.

Heil had recently come out with a lightweight headset, the Heil BM-10. For right at $100, I purchased one with the HC-4 element. The HC-4 was supposed to have a little bit more "punch", great for DX and contest work.

I was immediately pleased with how it performed. I used that headset for many years, many enjoyable contests. It was pretty comfortable, although after several hours, even the light touch on the  ears would cause a little irritation. The foam pads on the ears have been replaced a couple of times.

And then, in December of 2007, it quit. The microphone element stopped working. I disassembled it, determined that the element wasn't working, and it sat. I wanted to order a replacement HC-4 element. After all, Heil used to sell them. But no more.

After a while, I purchased a Heil Pro-set, perhaps one of the last ones made with the HC-4 element. It works spectacularly with the Elecraft K3.

So the BM-10 laid disassembled, for a suitable microphone element.

Electret microphone nestled in a bed
of foam.
This past January, I ordered an electret microphone element from Ramsey Electronics. It was probably one of the last kits they sold. The kit came with a resistor and coupling capacitor to isolate the bias. The capacitor was far too large to fit inside the 8-pin DIN connector, so used a smaller unit from the junk box.

I also replaced the boom mic clip. The original one had long ago cracked and was held together with a screw. Hell fortunately still sells them as a replacement part.

I had to do some hunting to find the microphone cover. The headset had been disassembled so long all the parts weren't in the same place.

Works like a champ. A bit of foam to keep the element from rattling around, and perhaps it is good for another dozen years or so.

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