I was suggesting to look at the parts list and see if the transformers are
different or the same.
As far as the H model you should be able to drive and load 3 572B's harder
and obtain the same power or close enough; it also reduces the stability
problem of 4 tubes in that circuit. The design is less than marginal. The
AL-572 is better in that respect. So is a Dentron Clipperton L with a bit of
rework.
Carl
KM1H
----- Original Message -----
From: "W7MJM" <w7mjm@arrl.net>
To: "Carl" <km1h@jeremy.mv.com>; <amps@contesting.com>
Sent: Wednesday, February 09, 2011 7:01 PM
Subject: Re: [Amps] AL-811 & 572's
> Carl,
>
> I didn't see anything on the Ameritron site that would answer my
> particular question, but perhaps I didn't dig deeply enough or think it
> through thoroughly.
>
> In any case, Colin, W7FM, and Bill, WA4LAV, seem to have explained it to
> me. I know the 811A to 572B swap has been discussed quite a bit, but the
> question as to why Tom, W8JI, recommends only 3 572B's in the AL-811H
> (with the fourth hole empty) had continued to puzzle me.
>
> I assumed one would want to drive the AL-811H, after retubing, to it's
> full 800 watts, so how could 3 572B's still deliver that output if they
> can't do it in the AL-811? The additional current draw of 572B's as
> compared to 811A's, and the need to reduce the AL-811H output to 600 watts
> hadn't occurred to me.
>
> So, as I now understand it, 3 572B's, with plate voltage in the
> neighborhood of 1500 volts, will deliver the same 600 watts as 3 811A's.
> So, assuming the power supplies are the same in the AL-811 and AL-811H,
> retubing an AL-811 gives you no increase or reduction in maximum PEP
> output (600 watts), just longer tube life, tolerance of overdriving, and
> tolerance of extended tuning, while retubing the AL-811H means sacrificing
> 200 watts of potential output (reduced to 600 from 800) in exchange for
> longer tube life, greater tolerance of overdriving, and greater tolerance
> of extended tuning.
>
> Do I have it right? If so, retubing the 600 watt PEP output AL-811 with
> 572B's makes sense, but retubing the AL-811H with 572B's is not
> necessarily beneficial, assuming you want maximum 800 watt PEP output from
> the four-holer.
>
> 73 and thanks to all who responded,
> Martin, W7MJM
>
>
>
> ----- Original Message -----
> From: "Carl" <km1h@jeremy.mv.com>
> To: "W7MJM" <w7mjm@arrl.net>; <amps@contesting.com>
> Sent: Wednesday, February 09, 2011 1:21 PM
> Subject: Re: [Amps] AL-811 & 572's
>
>
>> Go to the Ameritron site and find out.
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message -----
>> From: "W7MJM" <w7mjm@arrl.net>
>> To: <amps@contesting.com>
>> Sent: Wednesday, February 09, 2011 3:27 PM
>> Subject: Re: [Amps] AL-811 & 572's
>>
>>
>>> Is there anyone on the list who can answer my question as to why three
>>> 572B's in the three-hole AL-811 should only put out 600 watts whereas
>>> W8JI
>>> has suggested (if memory serves), that when retubing the four-hole
>>> AL-811H
>>> with 572B's, only three are needed and the fourth hole can be left
>>> empty?
>>>
>>> If an AL-811H retubed in this manner puts out 800 watts PEP, why not the
>>> AL-811? Is the power supply different?
>>>
>>> Waiting to be enlightened, but without any arcing. :-)
>>>
>>> 73,
>>> Martin
>>> W7MJM
>>>
>>>
>>> ----- Original Message -----
>>> From: "W7MJM" <w7mjm@arrl.net>
>>> To: "mitch cox" <ww4cox@embarqmail.com>
>>> Cc: <w8ji@contesting.com>; <w8ji@w8ji.com>
>>> Sent: Wednesday, February 09, 2011 10:36 AM
>>> Subject: Re: [Amps] AL-811 & 572's
>>>
>>>
>>>> Very interesting, Mitch. I think I'll just stick with the 600 watts
>>>> rated
>>>> output (my old Healthkit HM-2140 PEP meter shows 500 and my new MFJ-868
>>>> shows 800); obviously I need to calibrate the meters, but the drive is
>>>> about 70 watts so I'm probably putting out about 600 to 650 watts.
>>>>
>>>> With the three 572Bs in place, I don't have to worry as much about
>>>> tune-up
>>>> mistakes cooking the anodes, and the tubes seem to take up to about 100
>>>> watts of drive while staying under 165 mA on the grid current meter and
>>>> there are no reports of bad audio or splatter.
>>>>
>>>> The reason I wondered whether the trio of 572B's in the AL-811 would
>>>> put
>>>> out 800 watts is because Tom Rauch, W8JI, who designed the amp,
>>>> suggests,
>>>> when retubing an AL-811H with 572B's, that it's only necessary to
>>>> install
>>>> three 572B's and leave the fourth hole empty. So I figure, if three
>>>> tubes
>>>> in the AL-811H produce 800 watts of output, why not the same result in
>>>> the
>>>> AL-811? Is the power supply different?
>>>>
>>>> I'll cc Tom and see if he has any thoughts about this.
>>>>
>>>> 73,
>>>> Martin
>>>> W7MJM
>>>> ----- Original Message -----
>>>> From: "mitch cox" <ww4cox@embarqmail.com>
>>>> To: "W7MJM" <w7mjm@arrl.net>
>>>> Sent: Wednesday, February 09, 2011 5:18 AM
>>>> Subject: Re: [Amps] AL-811 & 572's
>>>>
>>>>
>>>>> If you wire the buck boost on the transformer to the highest voltage
>>>>> setting, 2200 VDC, 800 watts is a breeze but....you are also raising
>>>>> the
>>>>> filament voltage to a dangerous level. I tested one of these
>>>>> transformers
>>>>> in a home brew 2 months ago along with 3 Svetlana 572B tubes. At the
>>>>> highest voltage setting I got 900 watts out with 75 watts of drive. I
>>>>> also wondered about how stout this little transformer was so with good
>>>>> cooling, unlike the factory amp, and a separate filament transformer,
>>>>> I
>>>>> locked this home brew down at 900 watts CW for 1 hour, 20 minutes. No
>>>>> problems were encountered with either the tubes or the tranformer. The
>>>>> transformer was warm after the test but not hot and the amp will still
>>>>> produce 900 watts so nothing was harmed. At 85 watts of drive this amp
>>>>> will do a full KW with the same tubes as used in the test.
>>>>> ----- Original Message -----
>>>>> From: "W7MJM" <w7mjm@arrl.net>
>>>>> To: amps@contesting.com
>>>>> Sent: Tuesday, February 8, 2011 11:57:18 PM
>>>>> Subject: Re: [Amps] AL-811 & 572's
>>>>>
>>>>> "Thanks for the input guys. I'm aware of the limitations of the power
>>>>> supply
>>>>> on the AL-811. I was looking for performance information about the
>>>>> 572B
>>>>> tube
>>>>> itself."
>>>>>
>>>>> Isn't the power supply in the 3-tube AL-811 identical to the power
>>>>> supply
>>>>> in
>>>>> the 4-tube AL-811H? If so, shouldn't you be able to run the 3-tube
>>>>> AL-811
>>>>> at
>>>>> 800 watts PEP output when it's been retubed with 572B's?
>>>>>
>>>>> Anyone care to comment on this?
>>>>>
>>>>> 73,
>>>>> Martin
>>>>> _______________________________________________
>>>>> Amps mailing list
>>>>> Amps@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>>
>>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>
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