Centaur 411 Amp
Ed Tanton
n4xy@avana.net
Sun, 22 Dec 1996 17:56:10 -0500
I'm sorry Chuck... I think concern over a 12 hour drift of well under 100
hz for voice communications is absurd. Flame away.
At 09:29 AM 12/22/96 -0600, Chuck (Jack) Hawley wrote:
>Paul, Wv3j wrote:
>>
>> 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.
>
>So not we know that it doesn't have a step start....not unusual though
>for this price class but too bad anyway. I wonder if the (cheap), in
>series with the line current, thermister type of current limiting would
>be a good idea for these inexpensive power supplies (Astrons), amps and
>things?
>
>> Frequent arcing of the plate tuning capacitor.
>
>That's what Doug DeMaw said in the CQ "review" but I think he should
>have gone on to say "don't buy it". I pretty much decided to drop CQ
>magazine based on the superficial reviews that McCoy and DeMaw put out.
>They are both nice guys it seems and pretty smart cookies but if they
>won't be knowlegeable or straight about what they are looking at
>(subconsciously or otherwise) then who needs to pay 'em to do product
>reviews for the rest of us.
>
>> 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
>
>I'm not qualified to comment on the poor performance but I'm sorry to
>learn about these additional questions about the amp. I guess I would be
>wondering about the tubes also.
>
>> (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 woulda been disturbed by the scratches and chips. Is there a simple
>cover that can be replaced for 10 or 15 bucks that took most of the
>scratches? I always figured that I would be safe buying a TT because
>they could supply me with a new cover for most of their stuff.
>
>> 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
>
>Good luck. It's really difficult to deal with these well meaning, nice
>people when they just don't have the same technical rules and standards
>that you have. Although I'm sure that your reduced output on the higher
>bands is below their standards, I am reminded of the guys I know who
>tried in vain to like the Omni 5's and 6's that drifted or jumped 30,
>50, or 80 hertz from night to night on 75 Meter phone. It's not that
>important.....but darn it...it's frustrating when you spend a couple of
>hours to get it really close and then it's off again the next night. The
>factory thinks you're nuts to be nit picking like this....so eventually
>these guys drifted back to rice boxes that always end up at the same +/-
>3 hertz every night. Now we can do that in this country and it shouldn't
>matter why we want it.....the rest of the world seems to think it's
>important enough to do it and is willing to sell us expensive tcxo's.
>Now I know I'm going to hear a bunch of stuff about phase noise and
>crystal controlled oscillators....can't we do it with more stability?
>...even though it doesn't matter? I guess not....not with voltage
>controlled capacitors pulling the crystals and microprocessors
>correcting the master oscillator at least.
>
>I really want to say some more about my brain damaged TT auto tuner but
>it's discontinued and nobody seems to know anything about it, so I won't
>mention it.
>
>Paul, is there room for a bigger tune cap in there? Just wondering.
>
>73, Chuck, KE9UW
>
>
>--
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>
>
72/73
Ed Tanton N4XY EMAIL: n4xy@avana.net TEL: (770)579-3933 V/MBX/FAX
189 Pioneer Trail, Marietta, GA 30068-3466
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