In my experience using tetrodes without handles but from the same family, B+
needs to be substantially higher than Eg2 in order to protect Eg2 from harm,
and Ig2 generally decreases as Ep is increased; so, this ratio (Ep to Eg2)
appears somewhat critical in that it should be >5:1 or so...
WB2WIK/6
"Each success only buys an admission ticket to a more difficult problem." --
Henry Kissinger
> -----Original Message-----
> From: Jerry Flanders [SMTP:jflanders2@home.com]
> Sent: Friday, November 16, 2001 11:05 AM
> To: 2; AMPS
> Subject: Re: [AMPS] Checking out old amp
>
>
> 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?
>
> Jerry W4UK
>
> 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
> > >
> > >--
>
>
> --
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