[Collins] 30S-1 final 4CX1000 and 4CX1500 poor terminology

[jeremy-ca]

The 1000K was designed for TV translator service and as a military airborne 
AM linear. The solid screen ring raised the maximum frequency from 110 to 
400 MHz. It also requires a lot more air at the higher frequencies. I have a 
Westinghouse 8352 for a 222MHz amp that is under construction.

Carl
KM1H


----- Original Message ----- 
From: "Phil M." <pmills7 at comcast.net>
To: "Collins QTH.net" <collins at mailman.qth.net>
Sent: Tuesday, September 11, 2007 3:46 PM
Subject: Re: [Collins] 30S-1 final 4CX1000 and 4CX1500 poor terminology


> While I understand and have enjoyed the discussion, I believe the
> tube designation terminology has been very careless.  First of all,
> people have been talking about the 4CX1500 which is not very
> accurate.  The tube suitable for use in the 30S-1 is the 4CX1500B...
> please note the B.  According to the 1975 Eimac catalog, there is
> a 4CX1500A which has a filament requirement of 5 volts at 38 amps
> versus the 45CX1500B which needs 6 volts at 10 amps....a minor
> difference :-)  And, as someone pointed out earlier, the 4CX1500B is
> listed as designed for SSB with lower IMD.
>
> BTW, the same 1975 catalog lists a 4CX1000K with virtually the
> same characteristics as the 4CX1000A but with a solid screen ring....
> I've never come across one of these.
>
> 73, Phil
> W5BVB
>
>
>
> ----- Original Message ----- 
> From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
> To: "pete wokoun, sr." <pwokoun at hotmail.com>
> Cc: <collins at mailman.qth.net>
> Sent: Tuesday, September 11, 2007 1:32 PM
> Subject: Re: [Collins] 30S-1 final
>
>
>> On Mon, 2007-09-10 at 20:15 -1000, pete wokoun, sr. wrote:
>>> The 30S-1 I'm working on has a 4CX1000A final.  The tech manual also 
>>> lists
>>> this as the final.  I've heard and read about some amps having a 
>>> 4CX1500B in
>>> there.
>>>
>>> Is this a later model change?  I see the tubes specs are almost 
>>> identical
>>> except for the plate dissipation and filament current.  Can  they be
>>> interchanged in the 30S-1 or do you HAVE to use what's stenciled on the
>>> bottom side of the top cover, ie the 4cx1000A?
>>>
>>> pete KH6GRT
>>>
>> I don't think the 4CX1500 was ever a factory mod.
>>
>> Comparing the two data sheets there isn't a great deal of difference
>> other than plate and grid dissipation ratings and screen current
>> characteristics. The heater currents are the same.
>>
>> Because of better cathode to grid alignment, the 1500 claims less grid
>> interception of the electron stream which allows better linearity with a
>> bit of grid current and some grid current is allowed (grid dissipation 1
>> watt).
>>
>> Typical RF amplifier characteristics are with 225 volts on the screen of
>> the 1500 and 325 on the screen of the 1000. Since tube gain is directly
>> proportional to screen voltage, a mod that raises the screen voltage
>> will make the amplifier have more gain but may upset the tuning meter
>> and amplifier stability. A different screen voltage also can mean a
>> different plate load line is needed to keep the minimum dynamic plate
>> voltage is always above the screen voltage, else the screen gets
>> overloaded by gulps of current that used to be peak plate current
>> suddenly switching to the screen, and its not made for those several amp
>> peak currents.
>>
>> The typical data also shows the 1500 screen tends to run much more of a
>> negative current than the 1000.
>>
>> Other than the more negative screen current (which isn't a problem in
>> the grounded screen supply situation where the "screen" supply is also
>> carrying the total cathode current) it looks as if the 1500 makes a
>> decent and probably more linear replacement for the 1000 and the 1500
>> tolerates more grid drive without adding distortion or damaging the
>> grid.
>>
>> I'm always concerned with plate matching and plate tank components.
>> Raising the output from 1 KW to 1.5 KW raises the tank coil and loading
>> capacitor currents about 50% and that raises their power dissipation
>> more than double. The 30S-1 may have conservatively enough rated parts
>> to handle that increase. Not all finals can stand that, and the 1.76 dB
>> difference between 1 KW and 1.5 KW is far less than the second by second
>> changes in propagation and not something measurable with most receiver
>> S-meters. In the rare situation where propagation is steady and the 1 KW
>> signal is at the noise, that 1.76 dB increase may improve received
>> signal to noise ratio several more dB than the increase in power. In all
>> other situations it only runs up the electric bill.
>>
>> If it was me, I'd run the 4CX1500B at 4CX1000A ratings and expect a very
>> long tube and radio life.
>> -- 
>> 73, Jerry, K0CQ, Technical Advisor to the CRA
>> All content copyright Dr. Gerald N. Johnson, electrical engineer
>>
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>
>
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