ICOM IC-2710H microphone problem

[N9EJS]

I bought a used ICOM IC-2710H on eBay.  The owner's manual calls for a HM-98 mic.  The ICOM mic that came with it doesn't have a model number on it, but I subsequent learned there's a plastic cap (which I didn't receive with the rig) that has the model number on it, and I am suspecting that it is actually a HM-98S because it won't key the rig. 
I've read the 2004 postings at
http://www.eham.net/ehamforum/smf/index.php/topic,63133.0.html, which seem to have some bearing on my present problem.  I also have seen another discussion at
http://forums.qrz.com/showthread.php?327332-Icom-HM-98-vs-HM-98S.
I have a HM-133 that came with my IC-208H rig, and it works on the IC-2710H - but with high deviation.  I wonder if there is a modification of either the IC-133 mic or IC-2710H rig to adjust the high deviation problem.  N3MX seems to say in the 2004 eHam discussion above there's no potentiometer in the rig itself.  Thanks and 73 - George, N9EJS

[N9EJS]

I forgot to mention that I found a brand new HM-98S with cable, and it doesn't key the IC-2710H either!
73 - George, N9EJS

[KB5ZSM]

I would start by finding or creating wiring diagrams of each microphone. There are web sites out there with lots of microphone pin-outs. If that doesn't work, open them up and create your own wiring diagram. Once you do that, I'll bet the reason will be staring you right in the face. Those same diagrams may help in future trouble shooting also. http://www.mods.dk/ would be a good place to start. you could download your radio service manuals here and they will show the microphone connections.
Be carefull plugging microphones in radios that weren't made for them as you can do serious damage to both radio and microphone (e.g. shorting the 8 volt bias to ground and burning out the 8 volt regulator).

[N9EJS]

KB5ZSM - Thanks!  I'm working on it.  In the interim, I've found the HM-133 works with the IC-2710H, but has high audio deviation.  73 - George, N9EJS