[time-nuts] HP10811 losing EFC

[David McGaw]

Agilent part FUSE-THERMAL 115C, part no. 10811-80008, $3.97 ea. as of 
2 years ago.

I did have a 10811-60111 in a 5345A that had the thermistor open up 
which blew the thermal fuse.  The thermistor was interesting to replace.

73,

David N1HAC

At 09:08 PM 1/15/2010, you wrote:
>Several months ago, I purchased new thermal fuses from HP.  I can't remember
>how I came up with the part number, probably out of a 5061B manual or
>something, but when I searched Agilent parts, there it was.  It was only $3
>or $4 for the $0.10 part but it put it back in 'original' condition.  As I
>recalled, I found some very close values from one of the parts houses
>(Allied, Mouser??) and got those as back ups.
>
>If you need it, I can search for the details.
>
>Joe
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of Tom Holmes, N8ZM
>Sent: Friday, January 15, 2010 7:14 PM
>To: 'Discussion of precise time and frequency measurement'
>Subject: Re: [time-nuts] HP10811 losing EFC
>
>
>While on the subject of 10811's, I have one which appears to have a blown
>fuse. Bypassing same, it seems to work OK, so suspect that tiny filament or
>whatever simply succumbed to some shock or vibration, or maybe just old age.
>I don't recall the current draw now, but it seemed reasonable at the time,
>and it came up on frequency and appeared to be controlling the oven temp OK.
>
>
>Would like to replace the fuse with something more correct than a #22 before
>I let it go online full time.
>
>Any ideas for where to get replacement, or a suitable substitute?
>
>Thanks. This is a fun list to monitor. I learn more in a day here than
>anything else I've ever done.
>
>Regards,
>
>Tom Holmes, N8ZM
>Tipp City, OH
>EM79xx
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of Rick Karlquist
>Sent: Friday, January 15, 2010 7:54 PM
>To: Discussion of precise time and frequency measurement
>Subject: Re: [time-nuts] HP10811 losing EFC
>
>No one has mentioned the fact that the cathode of the varactor is connected
>to an internal 6.8V Zener diode voltage reference. This is another source of
>trouble.
>
>Rick Karlquist
>N6RK
>
>
>Bob Camp wrote:
> > Hi
> >
> > I sure would do some quick continuity checks on the EFC line before I
> > started swapping varicaps out. A bum solder joint opening up is a lot
> > more likely than the varicap going nuts in a fashion that still lets
> > the oscillator run.
> >
> > Bob
> >
> >
> > On Jan 15, 2010, at 7:08 PM, Neville Michie wrote:
> >
> >> Hi,
> >>
> >> I have two HP10811 oscillators that do not respond to EFC voltage.
> >> The latest to fail had been quite accurately set against a TBOLT, one
> >> morning (after being on standby in a HP5328A) it was off frequency
> >> and would not shift with EFC but would adjust with the coarse adjust.
> >> I have bought in two Phillips varicap diodes, BBY40 and BB149A, but
> >> before I did some damage fault finding in the HP10811s  I thought it
> >> wise to ask for any advice that was available. While I am playing
> >> with them I may try to readjust the temperature setting
> >> of the oven to get on top of the turnover. Can anyone point me to that
> >> article?
> >>
> >> cheers, Neville Michie
> >>
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> >
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>
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