Did you take a picture showing where the thermal fuse is located? I've never
opened a 10811.Sounds like a crude device as you described it. I've used
thermal fuses as a safety feature for fast-recharge medical NiCd battery packs
but those looked like big diodes.LarrySent via the Samsung Galaxy S20
-------- Original message --------From: Jared Cabot via time-nuts
<time-nuts@lists.febo.com> Date: 11/30/21 9:35 AM (GMT-08:00) To: Discussion
of precise time and frequency measurement <time-nuts@lists.febo.com> Cc: Jared
Cabot <jaredca...@protonmail.com> Subject: [time-nuts] Re: HP 5065A, no 2nd
harmonic. I was reading in a past thread on the time-nuts mailing list that the
thermal fuses can occasionally spontaneously go open circuit with age, far more
often than going open due to a real thermal fault.(I wonder how many have been
discarded over the years due to this issue?)They appear to be constructed from
two spring contacts held closed by wax. As the fuse heats up, the wax melts
allowing the contacts to permanently open.It would appear that age can cause
the contacts to open too... A common fix is a wire jumper (The fuse is
conveniently socketed, so a resistor leg offcut makes a nice jumper).I plan to
source a replacement thermal fuse, just to keep things a bit safer.Also, I did
get the pictures, thanks for that! I replied directly just now.Jared.‐‐‐‐‐‐‐
Original Message ‐‐‐‐‐‐‐On Wednesday, December 1st, 2021 at 02:05, Larry
McDavid <lmcda...@lmceng.com> wrote:> Do these thermal fuses fail spontaneously
or is there a common cause?> > If the "heater" transistor mounting screws were
quite loose, those> > transistors themselves might have overheated and failed.
But, a thermal> > fuse should fail by high temperature...> > Sounds like
progress, though. Cold OCXO means low frequency.> > Jared, I sent you a private
email with some pictures; did you get that?> > Larry> > On 11/30/2021 8:03 AM,
Jared Cabot via time-nuts wrote:> > > Well, I found it, the thermal fuse is
open circuit.> > > > If I briefly bypass it with a jumper wire, the oven pulls
the expected current.> > > > Looks like I need something that will trip at
roughly around 115C, rated to 1.0A> > > > (HP Part number 10811-80008)> > > >
Hopefully I can find something in Akihabara to make it easier to get my hands
on ASAP...> > > > Jared> > ...> ---> > Best wishes,> > Larry McDavid W6FUB> >
Anaheim, California (SE of Los Angeles, near Disneyland)> > time-nuts mailing
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