[time-nuts] (no subject)

Steve Rooke sar10538 at gmail.com
Sun Jun 20 18:36:43 EDT 2010


Bob,

On 21 June 2010 01:53, Robert Benward <rbenward at verizon.net> wrote:
> Steve,
> I was looking for insight.  For instance, is there a power up sequence for
> the +5 & +12V?  Anything I can look at before I dive in to the can?

I don't know the device but I seriously doubt there is a sequence for
powering it up and, considering it worked for you before, something
must have changed to cause this problem.

> This is not the first HP oscillator I have that has gone dead on me.  I have
> a 10811 that went south on me a few years back.  This is just getting
> expensive to replace them when they go bad.

What's the power supply voltages and quality you are using with these
devices. Perhaps the voltage is wrong or the PSU has let through a
voltage spike. Do you have enough current capability in the PSU to
startup the OCXO from cold as these take a lot of power initially and
then back-off when the oven gets hot. Check out the power lines with a
scope when you first apply power just to see if they dip or the PSU
starts to hunt up and down. If you don't have a scope, an analogue
multimeter may be able to show this better than a digital one.

> And yes, if there is someone out there that can do it, I would consider
> sending it out for repair.  I'm an electrical engineer, but I also know my
> limitations, and although it would grate at me to send it out for repair, it
> would be the right thing to do (if the price is right)

Well, I'm sure there is someone out there that can fix it for you but
you really need to find that someone who is willing to put in the time
and risk, plus the logistics of getting it to them. Are you worried
that there may be components inside which you do not have the
equipment, or skills, to deal with, possibly SMC, then that may be the
show stopper for you. Generally though, most of the faults on these
devices can be traced down to dry joints and such like so you may well
be able to fix that. The other area that may concern you is how do you
gain access to the inside as some units are fully sealed and would
need to be carefully cut open with something like a dremel with
cutting disk. Even if it's soldered closed, it's probably much safer
if you scrape the solder away until you break the joint. There is
really nothing that special inside if your careful documenting the
disassembly with photos and the like so that you can assemble it
correctly again. You'll probably have to replace the foam inside but
it should not be a challenge finding something suitable as there is
generally nothing special here providing you replace rough density for
density. The most important thing to remember is to take your time and
don't rush it. Collect as much information as possible. Google until
you have exhausted all possibilities on finding anyone who has dome
this before and then just go for it, what have you got to loose, and
you stand to gain by the experience let alone getting your oscillator
working again. Just make sure your not using a cheap PSU that is the
cause of destroying your expensive OCXO's.

Cheers,
Steve

> Bob
>
>
>  ----- Original Message -----
>  From: Steve Rooke
>  To: Discussion of precise time and frequency measurement
>  Sent: Sunday, June 20, 2010 1:03 AM
>  Subject: Re: [time-nuts] (no subject)
>
>
>  Well, if your not prepared to open it up to fix it yourself, are you
>  looking for someone else to fix it for you (your postings need
>  clarifying)?
>
>  Steve
>
>  On 20 June 2010 16:23, Robert Benward <rbenward at verizon.net> wrote:
>  > Adrian,
>  > I have all this stuff. I really don't want to open this thing up, and my
>  > oscillator trouble shooting skills are not that great.
>  >
>  > Bob
>  >
>  >
>  > ----- Original Message -----
>  > From: Adrian
>  > To: Discussion of precise time and frequency measurement
>  > Sent: Saturday, June 19, 2010 11:10 PM
>  > Subject: Re: [time-nuts] (no subject)
>  >
>  >
>  > Bob,
>  >
>  > guess you know that detailed documentaion is available here:
>  > http://www.prc68.com/I/HPE1938.shtml
>  > http://www.leapsecond.com/museum/e1938a/
>  > Open the can and report back!
>  >
>  > Adrian
>  >
>  >
>  > Robert Benward schrieb:
>  > > All,
>  > > Anybody out there know how to fix an E1938 oscillator? Something in
> the
>  > > metal can has crapped out. No 10MHz, and in turn, no processor action.
>  > It
>  > > worked a few months ago, turn it on today, and worked after about an
>  > hour.
>  > > Turned it on again this evening and nothing. I would hate to take that
>  > > crystal/heater assembly apart.
>  > >
>  > > Bob
>  > > _______________________________________________
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>  > >
>  >
>  >
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>
>  --
>  Steve Rooke - ZL3TUV & G8KVD
>  The only reason for time is so that everything doesn't happen at once.
>  - Einstein
>
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-- 
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein




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