[CentOS] Problems with kernel-3.10.0-693.5.2.el7.x86_64

Everyone,

I have two desktop units with : Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz
that do not allow the login screen to appear after the update of :
kernel-3.10.0-693.5.2.el7.x86_64 and kernel-3.10.0-693.2.2.el7.x86_64

Both of these units worked properly with
kernel.x86_64 3.10.0-514.26.2.el7

I am not sufficiently familiar with grub to know if the problem is
related to grub or related to the kernel.  I have been able to  boot
the machines by the use of kernel.x86_64 3.10.0-514.26.2.el7.

When using kernel-3.10.0-693 the login screen is blank and the login
prompt is missing, however each machine is accessible via the terminal
interface, or remotely with ssh.

Does anyone have any ideas ?

Greg