[time-nuts] RFTG RF Transistor - Identify RFTGM-II-XO Part (grosz)

Patrick Murphy fgdhrtey at gmail.com
Wed Jan 10 15:03:46 EST 2018


Thanks for the idea, Francis. I hadn't considered that. I'll keep that in
my kit bag as I work to resolve this. And I agree the temperatures of the
regulator and transistor are connected. I believe the regulator is
providing the bias. Given the output is some 27DB, that is a lot of
dissipation for such a small device.

I have had a couple of suggestions on what the part might be - MSA-0250 at
the top of the list. Looking at the data sheet, the maximum Tc is 200°C.
The device is designed to run hot. Comparing the XO unit with the Rb unit,
both are uncomfortably hot, with the XO being the hotter of the two. This
could easily be a difference in bias. With the MSA-0250 being near
Unobtanium, I'm hoping that portion of the circuit is actually operating
properly, and the problem is somewhere else. I'm going to reconnect the
units and resume diagnosing.

Thanks to you and the rest of the time-nuts for some very helpful
suggestions.

-Pat

On 12:41PM, Wed, Jan 10, 2018 Francis Grosz

wrote:

Patrick,

     I saw your Time-Nuts post on your RFTG problem.  If you are pretty
sure that the transistor has a problem and is not getting hot because
of some other fault, you might want to remove it and look to see if
the Part Number is on the bottom.  Depending on Board layout and
device pinout, those devices are sometimes mounted "upside down".
But with the regulator and transistor both getting hot, I'd suspect a
possible root cause leading to both of those.

          Francis Grosz



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