[time-nuts] Re: HP 5065A, no 2nd harmonic.

[Askild]

Hi,

Just a little warning.
Included are some pictures of a 10811 where thermal fuse protection have
not functioned.
I do not know why, if the fuse did not work, or somebody replaced it with a
wire, as this was in a HP 8663A that I found in a recycling bin, and I do
not know the history.


Regards,
Askild



On Tue, Nov 30, 2021 at 8:34 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> The thermal fuses die on their own far more often than they die protecting
> anything. The fuse is there to provide safety is certain odd situations.
> The
> simple answer these days is to replace it with a piece of wire.
>
> Bob
>
> > On Nov 30, 2021, at 12:05 PM, Larry McDavid <lmcdavid at 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)
> > _______________________________________________
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