[TenTec] re: Power supply and Centuar

[Paul, Wv3j]

DAVE-KA1ED (Who has no shift key) wrote:
>
>HI EVERYONE,
>
>I AM ENJOYING MY OMNI VI AND 962 POWER SUPPLY SINCE PURCHASING IT LAST
>FALL.
>
>I HAVE NOTICED THAT THE 962 EXHIBITS A NOTICEABLE HUM WHEN TRANSMITTING
>UNDER KEY DOWN LOAD AND A LESS NOTICEABLE HUM
>WHEN TRANSMITTING LESS THAT FULL DUTY CYCLE. ON RX SOMETIMES TOO.
>
>I BELIEVE THAT IT IS SOME TRANSFORMER HUM UNDER LOAD. HAS ANYONE
>ELSE NOTICED THIS TRAIT?  IS THIS COMMON PLACE FOR THE 961 AND 962
>SUPPLIES?  ARE THERE ANY FIXES OR MODS THAT ARE SUGGESTED TO CORRECT OR
>IMPROVE THIS CONDITION?
>
>TENTEC SERVICE WAS QUITE VAGUE AND PARTIALLY ADMITTED THAT SOME HUMMING
>MAY BE EXPERIENCED UINDER LOAD.  I WAS DISAPPOINTED IN
>THAT ADMISSION CONSIDERING THE COST OF THE UNIT.
>
>AS I HAVE A SMALL SHACK AREA AND CHASE MAINLY WEAK SIGNAL DX IT CAN
>BECOME DISTRACTING AT TIMES.
>
>ANY SUGESTIONS?
>
>TNX AND LOVE THAT OMNI!!
>
>73,
>
>DAVE-KA1ED
>
Dave,  

I also have a very quiet shack.  My solution to the power supply problem is
to use a small (6 Amp) supply to continuously float charge a very heavy deep
cycle marine battery, and to run the rig from the battery.

Many of the Astron power supplies have a worse problem.  It is common for
them to hum and buzz even when not under load.

Many readers will remember that I had a Centuar amp which had intolerable
fan noise.  I sent it back to the factory under the 30 day return policy.
You may also remember that I promised to let the reflector group know what
Ten Tec found wrong with the amp (symptoms were arcing and insufficient
output).  I intend to honor this promise, but to date Ten Tec has not
informed me what they found.  (Perhaps they hope to let a sleeping dog lie?
I hope it is just that they have been very busy.)  They did rather broadly
suggest that those having troubles might not know how to operate a grounded
grid amp.  This may be true in some cases, but my old SB-200 never
misbehaved, nor does my homebrew pair 3-500Z amp, so I excuse myself from
that group.

My homebrew amp also has intolerable fan noise.  I am using a Dayton 4C447
to pressurize the chassis.  I could get by with a third of its ait flow but
I had this one in the junk box.  I converted a pair of shooters headphones
(33 dB attenuation) by placing small speakers in the cups.  This lets me
hear very well but my blower can be heard by the stations I work when I use
the amp on single sideband.

Another noise control measure I use is to keep the computer out of the
shack.  This eliminates the computer's fan noise and its possible rf noise.

Now if I could just get rid of this ringing in my ears...

Paul Helbert


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