>
To: <amps@contesting.com>
>> Date: Thu, 11 Jun 1998 18:10:34 -0700
>> From: "Lane C. Zeitler" <km3g@cts.com>
>
>> Gents,
>> Looking for a "standard" to go by in regards to the Ip to Ig ratio of the
>> older triodes, ie 572B, 811A, 3-500Z, etc.
>
>There is no standard, it depends on many factors.
>
>> Can't find any published data/specs on the 572B Ig and apparently Eimac did
>> not publish and "max Ig" rating for their 3-500Z.
>
>That's because Ig can go all over the place depending on the
>application. With light loading the same amount of Ig will cause more
>dissipation than with heavier loading.
>
why?
>I think you asked a question about the AL-80A ratings. I looked for a
>manual, but no longer have one. I think you'll find the manual values
>you quoted are for tuneup, not during operation. As I recall,
>operating Ip is specified as a lower value, 400 mA.
>
>Eimac approved the operation of the 3-500Z according to Ameritron's
>instructions, and gave full warranty.
No copy of Eimac's supposed letter of approval for a 550mA anode-current
rating has been published. It seems a bit odd that the Heath SB-1000
instruction manual makes a similar claim about operation at unreasonably
high anode-mA. During a conversation c. 1990, Mr. Rauch told me that he
was the designer of the SB-1000. As I recall, at one time Mr. Rauch was
a co-owner of Ameritron.
>The SSB ratings were for IVS service, NOT CCS service as speced in the data
sheets.
This sort of dual-rating applies to indirectly-heated oxide-cathode type
tubes to prevent flaking of the barium-oxide and strontium-oxide emissive
coating during N-zero-N operation. However, since the 3-500Z's
tungsten-carbide emissive coating is epitaxially-bonded to the
tungsten-thorium alloy filament wire, the coating will not flake off, and
no such ratings apply. For directly-heated cathode tubes, the issue is
peak-emission capability for linear operation. For the 3-400Z/8163 or
3-500Z/8002 the peak anode-current emission capability c. 1200mA.
>If I'm not mistaken, the CW current ratings are 400 mA in the manual, and the
>550 mA is a tune-up only spec.
>
... seems unlikely based on my conversations with owners.
>IVS ratings allow higher power operation on SSB in ICAS service, IVS
>rating approval is or was subject to Eimac engineering approval
>
Not for directly-heated cathode tubes, Mr. Rauch. . What goes around
comes around.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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