[time-nuts] Efratom FRK - no 10Mhz oscillator

[Peter Bell]

Hi, Don

It's been quite a while since I worked on a FRK, but from what I
remember the only signals going to that oscillator board are power and
the control voltage. It might be worth checking the control voltage to
see if it's at a plausible value (nominal is 5V, spec range is 1V-16V,
IIRC) - if you have a spare xtal around, just try connecting it to the
pins on the PCB and see if it starts up.

I'm not aware of the xtals being failure prone - I have seen one FRK
with a bad one, but having seen the condition of the system it was
removed from, that was clearly impact damage.

Regards,

Pete


On Wed, Dec 21, 2011 at 1:29 AM, Don Lewis <dlewis6767 at austin.rr.com> wrote:
> A little help, pls, from the more experienced.  This is my first time into
> one of these .I have listened and learned from you' all for some time,
> though.  It can be intimidating in this close-packed FRK.
>
>
>
> I am trying to bring up an Efratom FRK  I have had for a while.
>
>
>
> The 10 MHz oscillator does not start upon power on.
>
>
>
> Any ideas where to look?
>
>
>
> I have done the following:
>
>
>
> *       I have it opened-up and applied 24vDC and the current starts up
> initially at 1.45 amp and slowly goes down to ~.6- .8 amps.
> *       Since I have no 10 MHz output, .so I looked at the oscillator board
> and nothing out from it.
> *       The 17 volt dc supply-rail is good, and the VCO input signal to the
> varacter control-circuitry is constantly ramping up and down slowly between
> ~1volt and ~15 volts.
> *       All the transistors in the oscillator circuit seem ok with a VOM,
> ..and when I purposely inject a 10Mhz signal into the collector of the
> 'oscillator' transistor (Q3), .I do get a clean 10Mhz out of the unit (of
> course it won't lock), .and I haven't even been into the rest of the unit.
> *       I think the crystal is bad, .I took the cover off the crystal oven,
> it 'looks' ok, . and the crystal heater in the oven is heating and
> regulating.
>
>
>
>
>
> Any ideas?  .does the 10 MHz crystal in these have a history of failing?
>
> Can I get a replacement  crystal for it easily?
>
> How can I test this crystal for pass/fail?
>
>
>
> Thanks, .just my first test of the waters as a fledging time-nut.
>
>
>
> Don Lewis
>
> Austin, TX
>
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