Centaur 411 Amp

[Steve Bookout]

Hello Paul, Steve, NJ4F, here.

I have owned a TITAN for several years and am wondering why, if arcing is
prevelant, TEN TEC doesn't do what is done with the TITAN, use polypropelene
with the caps.  In my amp there is, what appears to be, high density
polypropelene (HDPE) hanging between the plates of the tuning cap.  The
dielectric constant of HDPE is such that it increases the effective voltage
rating of the cap.  
I have modifyed caps like this using cut up plastic milk jugs; not pretty
but it works.

This problem reminds me of the same kind of problem the SB 220's had.  There
was a replacement cap available which was longer and had a higher rating.

Good luck and I will be watching to see what the outcome of this is.

73 de Steve, NJ4F

>After reading the Article in CQ and observations from other users (and as
>one who has been well satisfied with Ten Tec's gear and service) I ordered
>one of the demo Centaur 411 amps.  I am now about half way through the
>month's evlauation period.  The amp was clean inside and humidity was low.
>I warmed it up several minuits before beginninig to check it out into my kW
>dummy load and through my 238 tunner to an 80 Mtr loop antenna. I had
>several problems right from the start:
>
>        A loud THUNK on power up.        
>
>        Frequent arcing of the plate tuning capacitor.
>        
>        Low output indicated by the 411's and 238's wattmeters as follows:
>
>                f       Load    Tune    Ant     P (411)   P (238)  Notes
>
>                1850    10      7       loop    475       600     80mA grid    
>
>                3500    8.5     3.5     dummy   450       500
>
>                3670    5       3       loop    450       500     @1.6 kv
>
>                4000    1       2.5     loop    425       <500  
>
>                7.125   9       1.5     loop    475       500    1.6 kv,
>100mAg, 5000mAp
>
>                14.200  7       1       dummy   400       450    same w/ loop
>
>                21.200  7.8     1       dummy   250       150    
>
>Post conversion 28.100  7       1       dummy   50         40   100w in,
>120mAg, 400mAp
>
>(The old SB 200 loaded all these frequencies easily with no arcing and with
>full power indicated by the 238 (except 160 meters, which it was not
>designed to do)).  I thought maybe the 15 meter low pass filter might be the
>problem particularly on 15 mtrs, so I got the 10 mtr conversion from Ten Tec
>and installed it.  Unfortunately things remain as tabulated above, difficult
>to get a dip on 20 mtrs and above, with poorer  output as frequency is raised.
>
>Did I get an amp with bad tubes for my 5% demo savings or did I get a bad
>amp?  If the tubes are bad did the former operator of this demo amp maybe
>ruin them and maybe also arc the cap plates so much that they are now too
>close at melted edges?  I'd have thought a demo would have been gone over a
>time or two more than a new one.  I was prepared for (and not alarmed by)
>the small scratches and paint chips, but not for sub-standard performance.  
>
>I'm sure Ten Tec will make good on this as they have always done, but it is
>the beginning of the weekend, and Christmas shipping nightmare to boot.
>I'll call them Monday, but meantime I'd welcome comments from any of you as
>to the probable nature of these problems.
>
>Thanks and Christmas greetings too all.
>
>73,
>
>Paul Helbert - Wv3j
>
>              
>
>
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>
>


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FAQ on WWW:               http://www.contesting.com/tentecfaq.html
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Administrative requests:  tentec-REQUEST@contesting.com
Problems:                 w9tw@contesting.com
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