[ARC5] BC-453 mods

[Dennis Monticelli]

Yes.  The NPN transistor will need a couple of resistors for bias and a
bypass cap on the base, but it will stretch the operating voltage to
whatever your B+ preference may be.  It is not hard at all to find NPN's
rated for 300, 400, or 500V and they are in expensive.  A Darlington is
probably overkill for this application.

Dennis AE6C

On Sat, Aug 6, 2011 at 2:14 PM, J. Forster <jfor at quikus.com> wrote:

> Yes. Or a Darlington-White. I think it needs a resistor or two.
>
> -John
>
> ===============
>
>
> > That makes sense.  The JFET would be the input device and the bipolar is
> > probably a cascode connection (kinda like a grounded grid amp) to stand
> > off
> > the higher voltages.
> >
> > Dennis AE6C
> >
> > On Sat, Aug 6, 2011 at 1:15 PM, J. Forster <jfor at quikus.com> wrote:
> >
> >> I've seen two transistor versions, a FET and regular transistor, coupled
> >> together, used.
> >>
> >> -John
> >>
> >> ================
> >>
> >>
> >> > FYI.  A JFET is not a triode  It does have a "triode" like region
> >> prior
> >> to
> >> > pinchoff, but beyond that Vds bias point the current saturates like a
> >> > pentode.  The pinchoff voltage is low enough that it is rather
> >> impractical
> >> > ficult to run it as a triode in most cases.  But it's a good sub for a
> >> > pentode and you don't need any "screen" voltage.  The biggest
> >> limitation
> >> > is
> >> > the max operating voltage.
> >> >
> >> > Dennis AE6C
> >> >
> >> > On Sat, Aug 6, 2011 at 9:50 AM, Kenneth G. Gordon
> >> > <kgordon2006 at frontier.com>wrote:
> >> >
> >> >> Making the 1st IF regenerative in any of the models is easily done,
> >> >> and makes a big difference for weak signals....not so much for strong
> >> >> ones.
> >> >>
> >> >> Two pieces of #12 TH or THHN (with insulation still on) soldered to
> >> >> the grid and plate terminals, and a pot in the cathode is all it
> >> >> takes.
> >> >>
> >> >> The main problem I always had when trying to replace tubes with FETs
> >> >> is that an FET is basically a triode. For multi-grid tubes, this is
> >> >> often a real problem.
> >> >>
> >> >> For triodes, not so much.
> >> >>
> >> >> I have a pair of Tubesters here which I took out of a Heathkit VTVM.
> >> >> As I remember it, one replaced a 6AL5 and the other a 12AX7.
> >> >>
> >> >> vy 73,
> >> >>
> >> >> Ken W7EKB
> >> >> ______________________________________________________________
> >> >> ARC5 mailing list
> >> >> Home: http://mailman.qth.net/mailman/listinfo/arc5
> >> >> Help: http://mailman.qth.net/mmfaq.htm
> >> >> Post: mailto:ARC5 at mailman.qth.net
> >> >>
> >> >> This list hosted by: http://www.qsl.net
> >> >> Please help support this email list: http://www.qsl.net/donate.html
> >> >>
> >> > ______________________________________________________________
> >> > ARC5 mailing list
> >> > Home: http://mailman.qth.net/mailman/listinfo/arc5
> >> > Help: http://mailman.qth.net/mmfaq.htm
> >> > Post: mailto:ARC5 at mailman.qth.net
> >> >
> >> > This list hosted by: http://www.qsl.net
> >> > Please help support this email list: http://www.qsl.net/donate.html
> >> >
> >> >
> >>
> >>
> >>
> >
>
>
>