Testing AKG C-451 preamps/bodies

Hey everyone,
I recently picked up a pair of C451 preamps/bodies. They're actually C451L, with the 3-pin Lemo connectors. I've heard that they are electrically identical to the C451E.

I haven't had a chance to closely verify, but I believe my mics have the older, 3-transistor circuit, pictured on page 11 of this pdf:
http://www.coutant.org/akgc460b/akgcms.pdf

They don't have capsules, and while they look like they're in good shape, I was hoping there'd be some way to test these before buying capsules (as each one will cost more than what I spent on the mics themselves). Is there anyway to simply pot-down a line level signal and send it into the capsule end of the preamp? Or would there be some additional impedance concerns as well? Any advice would be appreciated.

The easiest way to do this is to borrow/rent some 451 heads.  Where are you based, lots of PA hire companies have decent stocks of C451.

Cheers,
Ruairi

You can test if you have an audio generator and a .1 uF cap. Wire the negative side of the generator to ground, put the cap in series between the positive side of the generator and the centre terminal in the top of the 451. Adjust level of the generator to see what level the body will take.
If you want to be really picky, you can use a cap the size of the capsule, about 50 pF. Then you can check the frequency response more accurately.
Watch for hum, you may need to shield the top of the mike with a bit of aluminium foil.

Thanks for the great suggestions. I actually work at an AKG dealer that does rentals, but since we mostly do live sound, we don't have anything nearly old enough to work with a 451L (or E, EB, etc.). After Ruairi's suggestion I started looking at the (supposedly) nicer rental places in the Chicagoland area and found that most of them have a pretty similar stock to my store with considerably higher prices-- no older 451s.

I don't know of any places that specialize in studio gear rentals around here, and since I wanted to test these quickly & cheaply, I went with radardoug's excellent suggestion. His recommendation of a 50 pF cap led me to check the AKG booklet linked above and it sez the capsule capacitance is 27 pF. So I dug around for a really small cap and the smallest thing I could find was a 250 pF silver mica. I'm not sure how critical this value is to noise performance, but both preamps worked. They were both pretty noisy, but I'd imagine a large part of that was the loose connections coupling the Lemo connector to an opened XLR cable, as well as my loose foil shield that I was trying to keep away from all those bare connections.

Thanks guys!