[time-nuts] HP10811 losing EFC

[John Miles]

> For a thermal fuse to make any use, it needs to be in the oven

Which this one isn't, in any event.  It's outside the oven and its
insulation layer.  Completely useless for protecting anything.

> but for
> pure over-current protection and external normal fuse will work, which
> is what he proposes. However, the trouble with dimensioning a normal
> fuse is that it needs to survive the heatup period, where as for a
> run-away oven the heatup never ends. The setability of the current limit
> of a fuse isn't particularly great so that it can be distinguished.
>
> The only way to achieve any meaningfull protection will be a thermal
> fuse. Only very little additional protection is achieved by a normal fuse.

It's worth noting that the 10811-60158 variant used in Z3801As does not
include a thermal fuse at all.  The OCXO module is similar to any other
10811, physically and electrically, but it's hermetically sealed so they may
not have been as concerned about outgassing.

If you really want to put a new thermal fuse in, check your local NTE
distributor for replacements, e.g. the NTE 8108, rated at 108 degrees C.
Not much point IMHO.

-- john, KE5FX