[Test-Equipment] Weller soldering iron problem

[WA2BPE]

Gentlemen:

Well, this isn't exactly test equipment but hopefully close enough for
this reflector.

Looking for info/schematic/idea on a Weller EC2002 supply with an
EC1503A iron.  The temp display initially flashes on upon turning pwr on
then goes blank.  Yes, the iron still gets hot.  Is a thermistor or ??
(for the temp control) in the iron opened up or??  Next, what to do
about it?

Ideas/info/suggestions, please; don't have any documentation.

Tnx & 73,

Tom - WA2BPE