[time-nuts] Identify RFTGM-II-XO Part

David G. McGaw david.g.mcgaw at dartmouth.edu
Wed Jan 10 12:45:49 EST 2018


Hi Dan,

That would be a MMIC amplifier.  Transistors have Q reference 
designators.  U's are ICs.  Take a look on the other side for markings.  
It appears to have been mounted upside-down.

David N1HAC


On 1/10/18 12:22 PM, Dan Kemppainen wrote:
> Patrick,
>
> It's possible that's one of the integrated RF amps, and not just an RF 
> transistor.
>
> You should be able to tell by tracing out the circuit. The inputs and 
> outputs will typically be capacitor coupled, with DC fed to the output 
> through a chip inductor or similar choke and resistor. There are some 
> other variations, but that's a pretty common style part.
>
> Here's and example. Although I doubt this is exactly what you have.
> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.minicircuits.com%2Fpdfs%2FERA-1%2B.pdf&data=02%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7C00427658632047168ebd08d5584e8f93%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C636512016803493571&sdata=MUR%2FKgKEJQeJRDNUK6ADoG4fGhQFxkNF31LVg6hzPlk%3D&reserved=0 
>
> If it's one of these style amp's, you may be able to find a compatible 
> part if you know the rough gain required and frequency of operation.
>
> It appears there is a mini circuits part close by, possibly tied into 
> this amp. Can you tell what part of the circuit this board covers? GPS 
> signal, etc?
>
> Dan
>
>
> On 1/10/2018 1:26 AM, time-nuts-request at febo.com wrote:
>> Message: 3
>> Date: Tue, 9 Jan 2018 23:33:33 -0600
>> From: Patrick Murphy<fgdhrtey at gmail.com>
>> To:time-nuts at febo.com
>> Subject: [time-nuts] Identify RFTGM-II-XO Part
>> Message-ID:
>>     <CAG1UqTg3dkjunSiOc=hrkxv7untygMKPT6XqSrfm9qMdwSD2DQ at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> My recently purchased RFTGm-II-XO threw a fault today. When I opened it,
>> the unmistakable smell of something way too hot was released. I guess 
>> this
>> is one bad aspect of the totally sealed enclosures these come in. 
>> Anyway,
>> when I plugged it in while open, I found U105, the microwave transistor
>> about centered in the attached photo was getting way too hot. It 
>> appears to
>> be an unmarked microwave transistor, probably part of the 15MHz output
>> circuit. VR101 - a 7815 on the far right is also getting pretty hot. I
>> expect the two are connected.
>>
>> Anyone have an idea of what the nomenclature for U105 is? Replacing 
>> it may
>> be a pipe dream, but knowing its name will be a good first step.
>>
>> Thanks for any assist.
>>
>> -Pat
>> -------------- next part --------------
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