On 10/16/2010 9:54 PM, Dale Svetanoff wrote:
> Doc,
>
> I don't know about that particular switching power supply, but I do know
> that I have done a lot of business over the past 10+ years with MCM, and I
> have found them very good to deal with. Unless someone specifically tells
> you that the unit is a "screamer", I'd suggest asking the person who takes
> your phone order if you can return it for RFI reasons. I will guess that
> they will allow that. It can't hurt to ask.
>
> I have been running the Astron SS-30M for several years now with NO
> problems whatever.
I ran two 30 A Astrons, one with the meters and one without. Both
failed within a year...actually the one with meters failed within about
two weeks, but it was simple. The fan failed and it shut down due to
heat. I called them and was assured they'd send out a new fan the next
day. I never received the fan, nor answers to an additional two e-mails
referring to the phone call and who I talked to. I didn't pursue it
farther as I had the needed fan. Fortunately the fan was the very same
as the one used in some of the older computers here at the time and I
had spares. Put a new fan in and it ran for close to a year before
failing and I *suspect* the failure was brought on by the earlier
failure of the fan. The other one lasted about a year. Both were quiet
as church mice. OTOH I also had the Icom PS-30 fail after 3 or 4 years.
It too was quiet and one day whey I turned it on...it didn't.
I also have the 50 and 30A conventional power supplies. Nary a problem
except for a screw that was laying on top of the supply fell into the
heat sink which was my fault for leaving it there. Unfortunately the
pass transistors are both hot and exposed which is a weakness for the
conventional supplies and should be taken into account when placing the
supply. The screw naturally caught between the the TO-3 case and
heatsink rendering the 50A PS inop with a loud bang. I replaced the
standard transistors with more rugged ones (for about the same price)
and it's been going ever since. (3 or 4 years so far). IIRC it's about
$60 or $70 USD for a complete set of pass transistors for the 50 A
supply. I have the TM-D710 in here on an RS- 35A.
At present I'm powering an Icom 756 Pro, Icom 7000, and a Kenwood TM-V7A
all off the 50A supply. Only one transmits at a time.
> (See QST back in 2002 - can't recall the issue - for a
> review of the Astron, and other, switching power supplies. The ARRL did an
> excellent job of testing several popular models - most of which are still
> available. Read the reviews then buy. That's why I bought the Astron; it
> was the lowest noise unit they tested.)
So far they are very quiet, but the reliability has not been all that
great, at least for me.
> A reminder: although keeping conducted emissions to a low level on the DC
> output lines is important for minimizing noise coupling from a switcher
> supply into the equipment it is powering, it is also important to be
> certain that you do not have any antennas located real close to the shack
> that could pick up radiated emissions from the DC cables or the cabinet of
> the power supply itself.
One 75 meter sloper runs almost directly overhead, but it's a good 50
feet to it. OTOH at roughly 1KW the LEDs in the shack start lighting up
and reach close to full brilliance by the time I hit the legal limit on 75.
73
Roger (K8RI)
> My HF antennas at the home QTH are more than 50
> feet away from the shack, and all point away from the shack. I have used
> the Astron on Field Day with HF antennas strung overhead and not had
> problems, so I do think it is a truly excellent unit. (No, I have no
> vested interest in Astron, but as an EMC engineer, I can tell good design
> when I see it. Astron does not spare the ferrites in their SS-series of
> power supplies.)
>
> I do own several pieces of Tenma test equipment. It all works OK, but none
> of what I have is a switcher.
>
> 73, Dale
> WA9ENA
>
>
>> [Original Message]
>> From: doc@kd4e.com<doc@kd4e.com>
>> To:<undisclosed-recipients:>
>> Date: 10/16/2010 10:47:49
>> Subject: [RFI] Noisy or Quiet Power Supplies?
>>
>> Anyone know if these things are RFI-quiet enough to be around
>> a Ham shack?
>>
>> Tenma Heavy Duty 40 Amp Switch Mode Power Supply
>> 72-7665 (727665) | MCM-Tenma Sale: $99.
>>
>> http://www.mcmelectronics.com/product/72-7665
>>
>> --
>>
>> Thanks!& 73, doc, KD4E
>> http://KD4E.com
>> Have an http://ultrafidian.com day
>> Defend free speech or lose your freedom.
>> I don't google I SEARCH! http://ixquick.com
>>
>>
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