[time-nuts] Re: Racal Dana 9457 Rubidium with intermittent lock

[paul swed]

I looked up that reference online and there is a blog on eevblog about it.
There is a front panel meter. Since the unit locks for a bit what is the
meter showing?
On efc, slowly drifting up or down.
Lamp voltage gives good hint to the lamp output. Is it stable or maybe
slowly dropping off.
Also the lamp could be dropping out and coming back on. They do that near
the EOL.
Best of luck. Looks like a nice unit.
Paul
WB8TSL

On Thu, Oct 12, 2023 at 1:34 AM Mark Hughes via time-nuts <
time-nuts at lists.febo.com> wrote:

> Hi
>
>   I have just started refurbishing an old 9475
>
> It did not work at all to start.
>
>    I have replaced all the 10 uF 35V caps in the Efratom FRK unit (one
> was dead short) and now it  powers up, achieves lock in about 7 min and
> works fine for about 1/2 hour.
>
> Then the lock light starts to flicker, within an hour it is more off
> than on.
>
>   When it is on, the lock seems genuine, I see the 10 MHz jump ( I have
> it on a scope  with the other timebase from a GPSDO at 10 MHz) and it is
> stable WRT that.   When showing unlocked, the 9475 10MHz off freq by
> about 0.05 Hz
>
>   Has anyone seen this behaviour before? I cant see any more
> electrolytics / tants to change in the FRK .  This sort of behaviour is
> typical  of failing electrolytics.
>
> The actual 9475  is good, it works with a different Efratom module with
> all voltages nominal and stable.
>
> The boards in the Efratom FRK don't quite match up with the schematic I
> have downloaded,  it's similar but not identical.
>
>   Thanks in advance
>
> Mark GM4ISM
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