Hello Rob,
I added auxiliary cooling to my TL-922 and it helped quite a bit. The layout
you describe sounds
nearly identical to the Kenwood, and I had the luxury of an access panel where
the PS strapping
was located for 120/240V operation. I removed the cover and mounted a fan
temporarily there to
blow air across the XFMR and other PS circuits. I was able to run it at 300W+
carrier for 5
minutes+ without any problems. I definitely recommend it!! BTW, I run a
Ten-Tec solid-state rig
on AM all the time, now into a Henry 3K-A. Very good combination.
Joe,
N3JI,
Lewisville, TX
--- "Rob Atkinson, K5UJ" <k5uj@hotmail.com> wrote:
> Hi folks,
>
> I am the owner of a 3 year old Ten Tec Centurion amp. This unit employs two
> 3-500ZGs on an elevated socket platform in the rear right side of the
> cabinet (when facing the front panel). On the rear left side is the h.v.
> power supply with a Dahl model 422 transformer which delivers 3.2 kv (around
> 2.9 under load) to the plates. Between the p.s. and rf deck is a rf shield
> running down the middle of the chassis. A square hole is cut in this
> between the tubes and p.s. and over that is mounted a Bi-Sonic tube axial
> muffin fan, model 4E-115-S21, sleeve bearing, 115 v. 220 ma 20 w. 2200 RPM
> moving 82 CFM. The fan is on the tube side of the shield, and draws air in
> through the left side of the cabinet, over the p.s. and exhausts it
> horizontally over the h.v. plate choke and tubes, including the pins and
> anode heat sinks, which are the flat type extending out horizontally. As
> most of you know, this has become the standard cooling method for these
> tubes in amateur amps since Heathkit began using it for the SB220.
>
> This cooling is adequate for low duty cycle modes for which the Centurion
> was designed, but I would like to use mine for brief transmissions (5 to 10
> minutes or less) of dsb carrier AM running a carrier of 200 to 250 watts. I
> have done this for a couple of minutes and the amp gets pretty darn hot. I
> would therefore like to boost cooling so as to avoid seal failure.
> Increased noise is not a problem for me.
>
> Bi-Sonic manufactures a fan that is identical to the stock fan but at higher
> rpm, and 20 more ma, 22 w. and 105 CFM, around a 25% improvement over stock.
> Is this an increase worth pursuing? Another possibility would be to add a
> fan to the external surface of the cabinet over the grill on the right side
> of the rf deck to speed up the draw of air to the right, out of the cabinet.
> Again, is this an improvement, and would it be worth pursuing?
>
>
>
> Overall, :
> A. Are these mods necessary
> B. Are there any comments on these methods
> C. Perhaps most important, is operating this amp on AM beyond its efficiency
> and heat dissipation design capability and should I keep it for SSB and CW,
> and look for something with higher plate voltage and/or tubes with higher
> plate dissipation / more cooling?
>
> Tnx,
>
> Rob Atkinson
> K5UJ
>
> p.s. to save you time and trouble, please no comments to run a plate
> modulated boat anchor.
>
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