[time-nuts] Help with my FTS4050...

Bill Hawkins bill at iaxs.net
Sat Jan 8 13:57:49 EST 2005


I mentioned the power supplies because everything else may depend
on those voltages, like a Tektronix scope. OTOH, you would expect
a separate regulator for the OXCO DAC because of the precision
required. I didn't say accuracy because the DAC is inside a feedback
loop, but it does need adequate voltage swing. 3.5 volts seems low
for the top of the range.

Of course, the oven has a great deal to do with the center frequency
of the crystal. If the supply voltage is limited or a heater joint
has raised in resistance or gone open, then you could not achieve
normal operation.

But these are all theories that can be settled by swapping the OXCO
or the DAC board. You could find the wire that supplies the control
voltage to the OXCO and try something higher than 3.5 volts, but
that won't fix anything. It is possible to raise the DAC control
voltage by one diode drop, using a bias resistor to something higher
than 5 volts. This must be done carefully without schematics, and
only if manually raising the OXCO control voltage works.

Too bad no one knows anything about the 4040.

Bill Hawkins


-----Original Message-----
From: Chuck Harris [mailto:cfharris at erols.com]
Sent: Saturday, January 08, 2005 10:14 AM
To: bill at iaxs.net; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Help with my FTS4050...


Hi Bill,

Not yet, but it would be a good idea.  Way back when, when I
was last working on this unit (10 years ago) they were fine.
I know that all of the supplies that are external to the FTS5000
module are ok.  I just opened the case of the '5000 last night
before bedtime, so I haven't gone too far yet.

-Chuck Harris






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