Sennheiser 816 - Deceased.
 

I am involved with a small independent shoot of a martial arts based feature in Western Australia.

The Sennheiser 816 is being used on a JVC HDV camera and phantom power is being supplied from the camera.

From go, some AC hum has been breaking into the sound to various degrees and has been attributed to the usual culprits such as dimmers and the power ducting all though an over 100 year old building, the Fremantle Prison in Western Australia.

Two nights ago, the Sennheiser finally expired. It is believed by the sound man that the mike has been dropped twice in its career. It normally lives inside a plastic wind enclosure.

They are presently using my Sony C74 which is made of brass and a bit on the heavy side for the boom man when at full stretch.

The same lead is being used to the Sony from the JVC with no hum problems, so the shielding on the lead doesn't seem to be at issue.

Does anyone have any quick info on what might be wrong and a possible in-field fix. - Regards to all from the location of "The Cage".

I assume that you have done the normal troubleshooting.

Just to be thorough, I suggest the following.

Connect the Sennheiser 816 directly, using a different, known to be good, cable to a completely different audio input on a different device. I suggest that you test it on a entirely different camera or mixer. Pleasee be certain to use not re-use any of the original cables, including any short ones that might be part of your wind enclosure.

I would also ensure that another microphone, another phantom powered one, works on the camera.

Stupid, but relavent question...Is this a MKH816P48? If it's a MKH816T, it requires a different flavor of phantom power, one which the HD100 cannot supply.

Greg and Dan.

Thanks for your responses.

As for checking the cable, we more or less did that when we substituted my C74 for the Sennheiser. The Sony mike is also phantom powered and works off the PD150 okay and also it seems, the JVC.

This might however account for why the JVC is going through batteries very greedily.

The Sennheiser had the name Sennheiser on it and 816, however I'll look closer to see if it has the other details on it.

The sound man told me that this mike is lighter than earlier Sennheiser 816s he has used so it well could be a latest model. It looks new.

Could you clarify what the phantom power issue is with the MKH816T. I assume the "T" hints at what is referred to as "T" power. Perhaps you could tell me what the two standards are in tech terms.

All I know is that the Sony wants 40v or so or a 9v stackcell internal battery. Because it has just worked on anything I have attached it to I have not delved into its high sciences as some things unknown are best left alone.

Thanks again for your responses.

Yes, the T is T power (or AB or parallel power).

Phantom power has equal voltages applied to pins 2 and 3 with respect to ground, usually over a 6.81k resistor. So pin 2 is at the same voltage as pin 3 and they are both 48v above pin 1 (ground). The 48v might be another lower voltage depending on the phantom power supply (12v, 15v, 24v, etc).

T power is 12 volts differentially on pins 2 and 3. So pin 2 might be 12 volts above pin 3 or the other way around.

You could measure the input that is supplying the power by sticking a volt meter across pins 1, 2, and 3 in different combinations and check that they read the appropriate numbers for the powering standard you are using. However, I don't know how you would do a simple test on the mic to see what powering standard it needs. Fortunately, as pointed out, they are usually labeled with a big fat "T" or in some other fashion.

Greg.

You nailed it. I asked the sound man today and the 816 has a "T" after its name.

Thanks everybody for your time and effort in contemplations of the problem and for a little furthur education I have experienced.

Regards from here in the West (of Australia).

Certain mixers, and other devices, can provide "T" power.

For example, the Sound Devices 302 can provide 12 volt T-power among other options such as both 12 volt and 48 Volt phantom power. (12 Volt phantom power and 12 Volt T-power are two different things and not interchangable.)

You could also purchase an adapter to convert 48 Volt phantom power to 12-volt T-power.

Another option is to obtain a stand-alone power supply that support T-power. Some of these will also provide 48 volt phantom power.

Don't sweat it Bob, I see that mistake a LOT! If you are interested, when I get home next week I will dig up a schematic for a DIY P48 to T power adapter. You can build it into an empty XLR M-F housing (like that of an in-line attenuator) and simply put this between the mic and the camera. These are available pre-made as well. Or an external power supply such as the Sennheiser BP-2 can power it. The 816 is a great mic, you should be using it!

Greg.

Thank you again for your advice. I spoke to the sound man last night and he would appreciate the schematic you mentioned, even a small circuit board diagram if you have it.

Also can you suggest a source or part number for the XLR M-F housing. Whilst this is Australia, most of this small volume stuff is bought in singly or in low volume from overseas. Just-in-time product distribution has invaded our shores and minimal local inventories are maintained these days.

One day, when a strategic situation develops, this practice is comprehensively going to bite our arse over here.

Alternately, PSC makes an inline adapter you might be able to find. Here's a link:

http://www.professionalsound.com/Catalog/adap.htm
or
http://www.trewaudio.com/catalog/items/item335.htm