[1000mp] delayed display turn on

Mon, 21 Jul 2003 10:27:23 +0300

Hi all.

It is a thermal fuse, not an NTC. It blew in my MkV and I had to replace
it. It is a 2A fuse that opens at 102=B0C.

This thermal fuse -topic was also discussed on the Contesting.com's
Yaesu-reflector about a year ago, and it appears to be a very typical
failure for the MP and MkV.

73, Esa OH7WV

-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Mort Arditti
Sent: 19. hein=E4kuuta 2003 18:57
To: [email protected]
Subject: Re: [1000mp] delayed display turn on

Hi,

        Re:   Yaesu 1000MP display

The details provided by Leo relating to the display suggests the reason
for the slow or blank display. The description by Mike Gilmer N2MG
states that there is a "...thermal fuse..". Possibly this thermal fuse
is not a fuse, rather it is an NTC thermistor. This will explain the
slow start up. When cold (room temperature), the thermistor will have
higher resistance, limit the inrush current and the display will be dim.
As it warms up, the resistance drops, current increases and the display
is bright. If indeed it is a thermistor (??), replacing it with a piece
of wire may not be a good idea. There will be no inrush current limit!
As the saying goes, "if it is not broke, don't fix it". So, I don't like
the idea opening my 1000MP and poke in. Possibly, someone who is working
on the radio, can measure the room temperature resistance of the
'thermal fuse' and the current profile. If it is a thermistor it is
possible to replace it with similar unit but higher ratings. The effect
may be slower turn on of the display. Another possibility is that the
device is a resettable solid state fuse. My vote is that the device is a
thermistor.

If someone has a non functional inverter board, I would like to have it
and try to figure out the details.

Thank you

73,

Mort, KB6BSN