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

[Wilko Bulte]

In general it is a very bad idea to defeat safety provisions that a manufacturer put in their product. They are there for a reason, any manufacturer would omit them, if only to save on cost. 

I would think no-one on this list would replace a blown fuse in their house fuse box with a nail. Or?

Wilko

> On 1 Dec 2021, at 12:13, Askild <megafluffy at gmail.com> wrote:
> 
> 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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