re[Elecraft] .: Switching Supplies

[Tony Morgan]

I find the fan noise on my MFJ-4125 unacceptable.
If I ever use it again it will have to be put behind the desk.

73,
Tony W7GO

ab2tc wrote:
> Hello all,
>
> I am using the MFJ-4125 25A switcher with my K3. I have no RF hash or
> birdies from the power supply at all. I find it unbelievable that popular
> and supposedly quality power supplies like the Astron would leave exposed
> transistor cases at elevated voltage above ground. The MFJ fan, which is
> always running, isn't whisper quiet, but not really noisy either. This
> switcher faired very well in the ARRL review a few years back, in fact it
> was one of the most quiet ones tested.
>
> Knut - AB2TC
>
>
>
> Mike Scott-7 wrote:
>   
>>> I also have an Astron RS35 and RS50 linear 
>>>       
>> supplies.  Sometimes the magnetic hum from them drives me crazy.  The
>> little
>>
>> cork pads Astron puts in them to alleviate this
>> does not help much. I keep them under the closed console on the floor.
>>                       Mike  WA8EBM
>> ----- Original Message -----
>>
>> I have my RS 35M on the floor also. I shorted it out once momentarily an
>> exciting moment. The problem is that the transistor cases that you see
>> sticking out of the back on the heat shield are at V+ level. If something
>> like a ground braid (this was my case) touches the transistors or the 12V
>> output terminal you have a short. 
>>
>> I ended up finding a cardboard box and cut the top and front off and most
>> of
>> the sides off. What is left is a cardboard "back shield" with lots of
>> ventilation to prevent accidental connections to the wire maze I have down
>> there on the floor.
>>
>> Mike Scott - AE6WA
>> Tarzana, CA (DM04 / near LA)
>> K3-100 #508/ KX1  #1311
>>
>>
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>
>