[R-390] RF subchassis separation

[Mark Richards]

Roy,

That was an excellent go/no go test.

Both crystals responded and therefore I can only assume they are 
oscillating.

I've some tube extenders, so will probe further...

Thanks for the suggestions.


On 03/13/2014 15:29, Roy Morgan wrote:
>
> Before you order expensive crystals, make this simple test:
>
> Hook the suspect crystal between the output of your signal generator and the RF probe on your VTVM.  Set a tenth of a volt output and low voltage range on the VTVM, and tune around the crystal frequency with the generator.  Slowly.  You’ll see a peak if the crystal is working.
Got to get me one of these.  Fell from need for one when I got into 
digital 30 years ago.  Time for a nice hamfest/flea market.
>
> You can make an RF detector with a diode, resistor and a cap if your meter doesn’t have an RF probe.
Ended up simply watching the output of the crystal on a scope.  Fine for 
these purposes.
>
> For the 200 kc crystal, you need a signal generator that goes that low.  The URM-25 is ideal.  *Some* audio generators go that high.
Used the URM25.

>
> All of this is extra justification to have TWO (or more) R-390A’s, or at least spare small crystal ovens equipped with the right crystals.
>

/K1MGY