Karl-Arne,
Just goes to show my guess was even high and I was trying to be low about it.
That get's it down to maybe 700 Vdc on the plates and that will probably not be
too good for IMD either. Plus at 800, the maximum dissipation was 10 watts over
and that's a lot for those tubes. I would about bet they would get hot enough
that their emission would be greatly decreased. I've never seen any of those
sweep type tubes last after cherrying up even once. After they do, and you try
them again, the emission falls off a good bit. Evidently it damages the cathode
permanently. That's about like the GLA-1000 that run 6LQ6's at 1200 Vdc. They
couldn't last any time at all. You can crank the plate voltage up a small
amount and get buy with it but any more and the life of the tube decreases. I
learned that the hard way years ago experimenting with sweep tube amps.
Best,
Will
*********** REPLY SEPARATOR ***********
On 8/10/05 at 10:05 PM Karl-Arne Markström wrote:
>Speaking of 'grossly abuse', I found some SSB ratings for the 6146
>family in my worn copy of the W6SAI 'Radio Handbook 18th Ed'
>
>If you apply a liberal definition of 'linear', it would be possible to
>run the 6146B with 800 V on the plate and 180 mA cathode current.
>A power output of about 90 W per tube would result.
>
>The down side is that the average plate dissipation would be 45 W instead
>of the rated 35 W,
>and the 3rd order IMD distorsion ratio of -19 dB, presumably referred to
>one tone.
>
>The on-the-air use of such an amplifier could make you a somewhat
>impopular neighbour.
>
>73/
>
>Karl-Arne
>SM0AOM
>
>
>----- Original Message -----
>From: "Will Matney" <craxd1@verizon.net>
>To: <amps@contesting.com>
>Sent: Wednesday, August 10, 2005 8:35 PM
>Subject: Re: [Amps] TV sweep tubes and 6146s
>
>
>I was thinking maybe 6 would get him 400 watts without pushing the tubes
>way past their ratings. They will be anyhow, but I wouldn't use over say
>+900 Vdc on the plates. That's still a good bit over the recommended
>maximum. You get up over 1 kV and bad things can happen. One has to
>remember those tubes have a maximum dissapation rating too. Over that and
>they'll cherry up. When they do, they'll be ruined. Most of those small
>glass tube like the 6146 and sweep tubes would drastically reduce their
>emission every time that anode would get red. Also, it's according to how
>he will run them, either grid driven or G-G. You'll get more out of them
>without burning them out running them grid driven. A few watts will open
>them up this way. G-G will need a good amount of drive for 6 tubes.
>
>Best,
>
>Will
>
>*********** REPLY SEPARATOR ***********
>
>On 8/10/05 at 1:45 PM Karl-Arne Markström wrote:
>
>>Without grossly abusing the 6146's, you cannot expect more than
>>about 250 W PEP output from four 6146 tubes.
>>
>>The reason that sweep tubes can give more power is that
>>they have very large peak emission capabilities.
>>
>>Peak emission in a 6146 is in the order of 700 mA, but i.a. the 6LQ6
>>was rated for about 1,2 A peak emission.
>>
>>To get 400W PEP, using a reasonable plate voltage,
>>out of parallelled small glass transmitting tubes would require 4 or 6 of
>>the TT21 class tetrodes
>>(as frequently done in small ship's radio equipment during the 70's).
>>
>>If you try this concept, it would be preferred to run the 6146's at a
>>higher plate voltage
>>rather to stretch the cathode current ratings.
>>
>>73/
>>
>>Karl-Arne
>>SM0AOM
>>
>>
>>
>>
>>----- Original Message -----
>>From: "Tom Bowman" <wa3rey@comcast.net>
>>To: <amps@contesting.com>
>>Sent: Wednesday, August 10, 2005 12:54 PM
>>Subject: [Amps] TV sweep tubes and 6146s
>>
>>
>>> What is the reason amplifiers never seem to be designed using four
>>> 6146s instead of TV sweep tubes like for example, four 6KD6s?
>>> I must be missing something obvious here.
>>>
>>> I'm asking because I'm thinking of building a 400W or so PEP amplifier
>>> for 75 and 40 meters.
>>>
>>> Keeping cost really low is one of my goals here and I have several good
>>> 6146s in the junk box.
>>>
>>>
>>> 73,
>>>
>>> Tom, WA3REY
>>> _______________________________________________
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>>>
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