On Feb 14, 2:29*pm, "D. Peter Maus"
wrote:
On 2/14/10 12:15 , bpnjensen wrote:





On Feb 14, 7:15 am, "D. Peter
wrote:
On 2/14/10 07:11 , Gregg wrote:

On Feb 12, 11:29 am, "D. Peter
wrote:
On 2/12/10 10:13 , bpnjensen wrote:

Pyramids are not especially popular with the Amateur Radio crowd:

http://www.eham.net/reviews/products/20

So I have noticed! *But the Astrons, in general, have a loyal
following.

* * *I did some research into the Pyramid supplies. As I said earlier,
they were not built for continuous service. Apparently, at any load.
Shame, too. With modification, they can be a pretty decent supply.

* * *Apparently Pyramid has been taking design tips for ICOM.

* * *

Ah Ha then, maybe dear old former friend wasn't lying then about
modding them. He was always modding something when I was over at the
shop. *He sure wanted them back pretty bad. Tough. :-I

* * They're nice supplies. And as you pointed out, you DID work CB
off of one for a couple of years without issue. But that was
intermittent service, which is what most of these supplies are built
for.

* * Most any supply will work for most applications. It's continuous
draw that does them in. But that's not a surprise. ICOM's, like R71,
R7000, R7100 are renowned for running so damned hot that the back
panel can be too hot to touch. Even the factory recommends going in
periodically and touching up solder joints, checking components for
heat damage.

* * And ICOM"s not the only one. But that doesn't mean it's not poor
design.

* * Which CB rig were you running, and what type of antenna did you use?

Peter - Shouldn't a 5 amp output supply be fully adequate to support a
CB, even SSB, that would require a draw of maybe 2 amp at transmit?

* *That's the point....How is that 5 amps measured? If the 5 amps
was measured to be steady for, say 5 minutes, that's considered
continuous service. In the case of 2 way radio, 'continuous' may be
also considered anything that is not 'peak.'

* *The point then becomes 'how does the manufacturer define their
terms Peak and Continuous?' And how do they measure these services.

* *If the power supply is rated at 5 amps continuous, one may safely
assume that 2 amp draw will be no problem. HOWEVER, how is that 5
amp service measured? 5 minutes? 10 minutes? Or do they run the
supply until the components reach constant temperature and then rate
THEN measure the continous output for a week?

* *Probably not.

* *Most of the time, the supply is built for intermittent service as
found in 2 way radio service. Short bursts, a minute or more, of
sustained current at rated output. In this case, 5 amps. And the
supply does it handily. But the components never reach constant
temperature.

* *That same power supply may, if run at 2 amps, reach constant
temperature, and the components may not survive that temperature if
run continously, ongoing. Read the user reviews at eHam of supplies
that have burned up resistors, even though used within their defined
ratings.

* *Consider. You can take a CB radio out of the box, hook it up and
converse for an entire 1500 mile trip without difficult. The
components are taking the full rated output--peak and continuous--of
the transmission for the entire trip. In bursts of conversation,
sometimes a minute, two minutes at a time.

* *But that's intermittent service. Tape that key down and let it
transmit indefinitely. It will fail. And pretty quickly. The
components were rated sufficiently for peak current during voice
peaks, and continous current during a conversational segment, but
not for continous broadcast. Neither the power input regulators, not
the finals will take a full load indefinitely. Even though current
can be many times average. Even though the power throughput never
exceeds rating.

* *The radio used for conversation will be trouble free for years.
Used as a broadcast device, it will fail quickly.

* *Pirates like to use Ham rigs for their broadcasts. These have to
be modified for the duration of a broadcast to meet the extremes of
continous ongoing service. Even rigs built with conservatively
rated, quality components will not be able to meet the demand of
continous ongoing service. Though the same rigs will be in use all
day, every day for 2 way conversation without issue.

* *It all depends on HOW the power supply ratings are determined.
Very few are tested with continous ongoing service in mind. Because
that's not what they're purchased for.

* *So, that 5 amp rating may be illusory. And though 2 amps may seem
logically assumed to be a safe, and troublefree, output for a 5 amp
supply, if the components were selected with intermittent service in
mind, they may find that 2 amps takes them more slowly to constant
temperature, but they do reach constant temperature, where they sit
and cook until they fail because they're not sufficiently cooled.
And because the supply is built with intermittent service in mind,
component cooling is less of a priority, and not a design
consideration beyond the minimums.

* *That's why when selecting a power supply, current ratings are
usually meaningless unless you know how they were determined.
Assumptions may be made, but you have to know what assumptions the
manufacturer was making as well when the device was designed.

* *Read the eHam reviews of some of these supplies. Failure after a
short time at current draws well within the performance curve.



It is true, the Icoms run hot - specifically with the R75, it is
likely the power brick, which supplies almost 50% more voltage to the
unit that it requires (near 18 volts).

* *The regulator, and the load draw down of the supply, itself,
brings down that voltage. The heat is generated by the regulator,
but generates so much heat that nearby resistors burn because they
can't cool themselves.

* *The voltage input to the regulator is higher than the operating
voltage at the output of the regulator so that there is something to
actually regulate. It's this extra power that's dissipated as heat
by the regulator. If there's a voltage sag due to peak draw, or
lower input voltage, there's some play for the regulator to work with.

* *And the brick, itself is a 'just enough' supply...providing
sufficient current for the operation of the radio, with a modest
reserve so when all functions are active, and volume is high, audio
peaks don't draw more than the radio can access, and modulate the
supply rail. *But the very load of the radio itself will draw down
the voltage of the brick in operation.

* *Measure the voltage of the brick open circuit. 18 v. Now measure
the voltage output while the radio is in operation....the voltage
will be lower. Closer to 14. This PS is designed with this occurence
in mind, and it's normal. A bigger supply with a 12-13.8 voltage
input to your radio will provide the same current as the brick, and
the radio will get just as hot.- Hide quoted text -

- Show quoted text -

Great post Peter, I printed that out to save it.:-)