[Amps] Can I cool too much the tubes?

Fri Aug 20 09:20:53 PDT 2010

Gentlemen,

You should take a look at the plate dissipation at the reduced power levels.

In my amp, as the power output drops back, the efficiency drops at a faster 
rate on some bands.  Which means that running the amp at half power, for 
example, as is the current rule of thumb for RTTY operation, may not 
actually reduce the effective plate dissipation very much.

Of course, one point does not make a trend.  But it's easy to make the 
calculation and then a guy can KNOW rather than just guess.

And if we were perhaps talking about an SB220, that transformer is pretty 
light weight to begin with, and a guy would definitely want to check the 
efficiency there.

Hope to see you in the SARTG.

73/jeff/ac0c
www.ac0c.com

--------------------------------------------------
From: "Rob Atkinson" <ranchorobbo at gmail.com>
Sent: Friday, August 20, 2010 10:09 AM
To: "Patrick Barthelow" <apolloeme at live.com>
Cc: <amps at contesting.com>
Subject: Re: [Amps] Can I cool too much the tubes?

> Pat,
>
> I have the amp, manual with schematic.  There is nothing in there
> about any sensor that throws the amp in standby if it gets too hot.
> That's why I asked.
>
> It must be an aftermarket mod in your amp Rudy.
>
> But, I am always willing to be surprised and eat crow. Why not give
> Ten Tec a call and ask them?   There might be something in there
> having to do with current draw I don't know about, thay may have been
> taken out in later models.  Anyway, my comment about specifiying mode
> was not directed at you.
>
> It's up to you whether or not 400 w. is enough, but in my opinion a
> new Alpha is not the answer if you want a really robust amp.  If you
> can afford a new Alpha you can afford an old one back before they
> tried to jam everything into a teeny desk-top cabinet, or an old
> Henry, or two, or homebrewing one in a rack....maybe an old TMC or
> Collins commercial communications amp...
>
> On Thu, Aug 19, 2010 at 11:40 PM, Patrick Barthelow <apolloeme at live.com> 
> wrote:
>>
>> Does anyone have a schematic for the amp under discussion, or perhaps 
>> looked
>> to see the sensor device that senses excessive heat to
>> trigger a shutdown?  I am curious what they sample for the  heat trip
>> function.    And, if it is an internal sensor for the transformer core, 
>> it
>> might not help,  but perhaps some extra muffin fans, mounted external or
>> internal to the amp could add enough cooling to extend its duty cycle on
>> RTTY.
>>
>> Back in the olden days, as a kid, I used to sit a muffin fan right on top
>> of my Drake TR-4 Finals Cage, drawing upward, and the whole radio became 
>> and
>> ran dramatically cooler.
>>
>> Best Regards,
>> 73, de Pat Barthelow AA6EG
>>
>>
>>
>>
>>> Date: Thu, 19 Aug 2010 20:16:13 -0700
>>> From: r_bakalov at yahoo.com
>>> To: amps at contesting.com; ranchorobbo at gmail.com
>>> Subject: Re: [Amps] Can I cool too much the tubes?
>>>
>>> Rob,
>>> I am the second owner of this amp and don't know its age. It is the grey
>>> model. I can certainly look up the serial number when I am back to VE3 
>>> where
>>> my contesting QTH is.
>>> As far as mode goes, my very first post noted that this is with respect 
>>> to
>>> RTTY where I can't really run it longer than 30 min at full power.  I am 
>>> not
>>> a SSB guy; CW runs all day long at full power. Standby or not, some sort 
>>> of
>>> protection kicks in when the amps gets too hot and the orange STBY LED 
>>> is
>>> on.
>>> So now my dilemma is if I should run low power, without the amp, or high
>>> power at only 400 W during the upcoming CQWW RTTY contest :-) Or time 
>>> for an
>>> Alpha :-)
>>> Rudy N2WQ
>>> --- On Thu, 8/19/10, Rob Atkinson <ranchorobbo at gmail.com> wrote:
>>>
>>> From: Rob Atkinson <ranchorobbo at gmail.com>
>>> Subject: Re: [Amps] Can I cool too much the tubes?
>>> To: amps at contesting.com
>>> Date: Thursday, August 19, 2010, 4:28 PM
>>>
>>> Rudy,
>>>
>>> Is this automatic standby mode protection a new thing with the
>>> Centurion?  Mine is around 10 years old and it has nothing like this.
>>>
>>> When did you get yours?
>>>
>>> N.B.  When you guys write about transmittion time at some power level,
>>> it is very important that you specify the mode.
>>>
>>> There is a huge difference between "1.5 KW no time limit (operating
>>> SSB) and 1.5 KW no time limit carrier.
>>>
>>> SSB is the "Coors Light" of transmission modes.
>>>
>>> 73
>>>
>>> Rob
>>> K5UJ
>>>
>>>
>>> On Wed, 18 Aug 2010 10:34:58 -0700 (PDT), Rudy Bakalov
>>> <r_bakalov at yahoo.com> wrote:
>>>
>>> >Experience trumps specs. The amp goes into standby mode after about 30
>>> > minutes
>>> >running at full power, i.e. about 1200 W.  If I run it at around 
>>> >400-500
>>> > W it
>>> >is fine.
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
> 