[time-nuts] Morion MV89 output level?

[Tom Miller]

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Message: 2
Date: Wed, 08 Feb 2012 22:15:41 -0600
From: Scott Newell <newell+timenuts at n5tnl.com>
To: time-nuts at febo.com
Subject: [time-nuts] Morion MV89 output level?
Message-ID: <mailman.980.1328767168.1783.time-nuts at febo.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

Got my replacement FE-5680 and a MV89 in from Nichegeek.  I figured
I'd better power up and check the MV89 before I let 'em know
everything was ok.  The MV89 is warming up nicely, the current is
down to 290 mA (and still dropping), but the output seems low; about
40 mV RMS as measured on a scope with a 10Meg 10x probe.  (Datasheet
spec is +7 +/- 2 dBm.)  The output is too weak to reliably trigger my
5345A counter.

The reference voltage measures 4.90 VDC.

If anyone can make a quick measurement on their MV89, I'd appreciate it.


thanks!
newell  N5TNL




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It seems that many of these oscillators have an internal problem with a 
output coupling capacitor. Yours does in fact have this problem. You will 
need to open the package up and replace a chip capacitor to get ti to work 
right. This capacitor is right next to the RF output pin.

I told the seller about the problem and this is their reply:
_____________________________
"Hi Tom,

Thanks for letting us know about that.

As you may know, this is
an secondhand item and some unwelding problem may happen to capacitor
inside.But it can be good with general application. If you need it for high
precision, then you have to check the circuit and fix it by yourself.

1.
Many units (about 50%) would have about 20dB output less than 7dBm. It is
said that the inside coupling capacitance would separate from body while
outputting, which leads to being invalid.
2. Some units become normal when
the temperature is stable, but they would fluctuate during the process
heating from cold to stable. Actually, it is the same problem as the above
situation. The units can be observed the output waves when  it comes to
stability.
3. Tuning frequency has parasitic amplitude modulation effect,
and 5MHz output can be seen in normal MV89 Output spectrum."
_____

I just did two of them. Once this is fixed, the units work very nice.

Regards,
Tom