[time-nuts] Re: Efratom M-100 102 not locking

[Bob kb8tq]

Hi

The M100 series *should* have a replaceable bulb in it. They also are discrete part designs. Both of those
things make it possible to repair them. That’s the good news.

The rest of the story:

Typical operating time without a heatsink is a couple of years. I have a lot of empirical data on that. With
proper cooling they should run for at least ten years. It’s MTBF rather than wear out so who knows what 
your result would be. 

Things like schematics and repair manuals are not all that easy to find.

Back in the day, you could buy a replacement bulb. I have no idea if that’s still true or what the cost would
be. They are very much a custom part. Back in the day, we seemed to get 10+ years out of a bulb. This
is a wear out issue. It does not appear to be impacted by temperature. 

The typical first step is to pull the bulb and gently heat it up. See if that gets the Rb moving around inside.

Fun !!!

Bob

> On Nov 27, 2025, at 11:15 AM, Peter Gottlieb via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I have this Rb oscillator which has output but won't lock.
> 
> Are these repairable?  Worth the effort?  Date code is from 1989 so it may have a lot of hours on it.
> 
> Peter
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