sql sum and case

I've using a sql case statement to sum up measurements.
This is working fine, except now I would like to add an ELSE clause and I can seem to get it to work.

As a note(in case it matters) The below code is copied from SQL Server where I'm testing the original sql statement, but in actuality the code will be run from RPG using Scott's JDBCR4

Below is an excerpt from the sql statement that works.

select
sum(case
when maintype <> 'Transmission '
and Diameter <= 2 and Material = 1
and (inServiceDate < '2014-11-01' OR InServiceDate IS Null)
then measuredlength end) as
'P2_1' ,
sum(case
when maintype <> 'Transmission '
and Diameter <= 2 and Material = 2
and (inServiceDate < '2014-11-01' OR InServiceDate IS Null)
then measuredlength end) as
'P2_2' ,
sum(case
when maintype <> 'Transmission '
and Diameter <= 2 and Material = 3
and (inServiceDate < '2014-11-01' OR InServiceDate IS Null)
then measuredlength end) as
'P2_3'
FROM MAINSVW

I want something like this, but can't make it work.

select
sum(case
when maintype <> 'Transmission '
and Diameter <= 2 and Material = 1
and (inServiceDate < '2014-11-01' OR InServiceDate IS Null)
then measuredlength end) as
'P2_1' ,
sum(case
when maintype <> 'Transmission '
and Diameter <= 2 and Material = 2
and (inServiceDate < '2014-11-01' OR InServiceDate IS Null)
then measuredlength end) as
'P2_2' ,
sum(case
when maintype <> 'Transmission '
and Diameter <= 2 and Material = 3
and (inServiceDate < '2014-11-01' OR InServiceDate IS Null)
then measuredlength end) as
'P2_3'

ELSE
sum measuredlength as 'unknown'

FROM MAINSVW

Thanks

Mike
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