XTL5000 secure modules problem with O5 head

[radioinstl]

We have a number of XTL-5000's with W4 and W7 heads. They have DES-
XL/DES-OFB UCM's on HLN6876B 3 day retention boards. We we have been
upgradeing to O5 heads, the Secure modules no longer are seen by the
radio or able to be used in the radio once upgraded to the O5 head.
We noticed in our newer XTL5000's that came with O5 heads, they have
MHLN6918B 3 day retention boards and works fine. When I look up the
HLN6876B on MOL it shows that it has been replaced with the
MHLN6918B.

Does anyone have any paperwork to this effect? SRN etc? or any word
from Motorola on what is being done for excisting customers that are
upgrading thier radios to the new head

[Astro Spectra]

The HLN6876_ doesn't work with the O5 head as you've found. That’s why they’re turning up on eBay.

I understand that the official reason is because of height restrictions in the between the front of the radio drawer and the back of the O5 head. In other words the UCM and carrier board stack is too thick.

However, if it was just a matter of space then you’d expect the old board to still work with the head spaced away but it doesn’t. I suspect it is something to do with serial bus comms with the head, possibly an address conflict.

Just budget on getting a new carrier with each Odyssey upgrade or get your account rep to give you new boards as a customer accommodation.