Fine scale time plot labeling

["E.D. (Ned) Cokelet" <cokelet@xxxxxxxxxxxxx>]

Can anyone tell me why the following script does not produce a plot with 1 hour
as the major time axis interval and 10 minutes as the minor one?
*********************************************************************************

! Define an axis and grid

define
axis/t="23-aug-2001:20:30:00":"23-aug-2001:20:40:00":`1/4`/units=sec/t0="23-aug-2001:20:30:00"
tax1

define grid/t=tax1 tgrd1


! Invent a variable and plot it

let tm1 = t[gt=tgrd1]
let v1 = 4*tm1

plot v1

! Plot looks OK, but let's zoom in on the time axis

pause


! Plot on an axis with hour/minutes as major/minor time interval

plot/set v1
ppl txtype,hr,min
ppl txlint,10,1

ppl plot

******************************************************************
--
Edward D. (Ned) Cokelet, Ph.D.      cokelet@pmel.noaa.gov
NOAA/PMEL                                   ph: (206) 526-6820
7600 Sand Point Way NE                   fax: (206) 526-6485
Seattle, WA 98115-6439

begin:vcard 
n:Cokelet;E. D. (Ned)
tel;fax:(206) 526-6845
tel;work:(206) 526-6820
x-mozilla-html:FALSE
org:NOAA/PMEL
adr:;;7600 Sand Point Way NE;Seattle;WA;98115-6439;USA
version:2.1
email;internet:cokelet@pmel.noaa.gov
title:Oceanographer, PhD
x-mozilla-cpt:;3
fn:Edward D. (Ned) Cokelet
end:vcard