No sound from Mack !!!

Sounds like the C26 may be faulty. 

Tried all that....still nothing....

So you have the 7100 outputs going into the C26 Amplifier Output terminals?
And you have a RCA cable going between the C26 Main Output to the 7100?
And you have all pushed the buttons to make sure nothing is set incorrectly?
Are you sure you have the speaker connections correct? The older C26 had odd colored terminals.
Try plugging and removing a 3.5mm jack into the headphone socket a few times in case it is shunting the load due to stuck internals.

Fuse OK......amp connected to pre amp

I have a C26 in my secondary system. As imfihifan stated, you have to first connect the preamp to the amp. Then connect the speakers to the C26, main and remote.

Blown fuse from all the testing?

Set up as suggested by Imfififan......No sound ???

According to the C26 Manual http://wegavision.pytalhost.com/McIntosh/C26_own.pdf

SPEAKER SWITCHES
To switch the main and remote stereo speakers using the push buttons on the front panel, the power amplifier output leads must be connected to the amplifier output terminals on the rear of the C 26. The main speakers must be connected to the main speaker terminals and the remote speakers to the remote speaker terminals. If either main or remote speaker button is pushed to OFF, load resistors are automatically connected to the power amplifier to compensate for the speaker.

And the (back of the( 7100) only has provision for one set of spkrs /??

OK
I'm getting that, and that's what i'm doing now, but why would they put the main / remote facility there? I would like to add SVS bookshelf as well
                                     Jeff....

If I'm getting this right, you are trying to connect the speakers to the preamp (C-26)?

If so, your second explanation is what you should be doing. Connect the speakers to the 7100 and then connect the C-26 to the 7100. The C-26 is your volume control and you also connect your sources to it.