>
>Thanks
>
>I can easily apply around 1KV to the big tube's plate by jumper from the
>driver amp's plate power supply. Would that protect it OK?
>
Probably not. I would not plug the tube in until all four voltages are
in the ballpark. / There is a typo below. The anode must be much more
positive than the screen or too many electrons will go to the screen and
screen current will be excessive.
cheers, Jerry
>
>At 10:57 AM 11/16/2001 -0800, 2 wrote:
>> >
>> >Should I worry about damaging the output tube?
>> >
>>/ If the screen supply is not fused or current limited, applying screen
>>V without anode V is not good.
>>
>> >I need to power up this old 5CX3000A pentode amp in a limited way to
>> >proceed with my checkout. I am nowhere near to applying HV and drive yet,
>> >but think I have the bias and SG supplies operational and need to check out
>> >a few voltages and circuits. There is a ton of supporting/protective
>> >circuitry that I want to observe and try to understand (no schematics).
>> >
>> >I am concerned about powering up the main tube because I read warnings
>> >about operating without plate HV, but perhaps this doesn't apply as long as
>> >there is no drive.
>> >
>>Drive makes no difference. If the anode is mucho positive it is not
>>sucking up electrons, the electron go for the screen and screen current
>>is astronomical.
>>
>> >As far as damage to the big tube is concerned, should I be worried about
>> >damage to it if I power up all but the drive and HV? I KNOW I have bias on
>> >grid 1. I am not sure the screen grid actually has voltage until I smoke
>> >test, because it looks like that circuit is awaiting some relays to pull in
>> >that probably will in this next step. Any tips/advice/whatever?
>> >
>>Screen V and anode V should be there when the grid is biased off.
>>There's some info and photos of AB1 amps on my Web site.
>>
>> >cheers,
>>Jerry
>> >
>> >--
>
>
>--
>FAQ on WWW: http://www.contesting.com/FAQ/amps
>Submissions: amps@contesting.com
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>Problems: owner-amps@contesting.com
>
>
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
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