[ARC5] T-19 Update

[Mark K3MSB]

On Mon, Dec 17, 2012 at 6:09 PM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> On 17 Dec 2012 at 18:00, Mark K3MSB wrote:
>
> > I did test all tubes on my Hickock and they tested OK (but of course
> > that really doesn't stress PA tubes).
>
> Correct. The only real test of a tube is substitution of a known good one.
>
> > I'm using a Heathkit IM-11 VTVM for measurements via a small alligator
> > clip.  I'm only measuring one item at a time.
>
> That will still only measure DC or low frequency AC. At DC, its input
> "resistance" is 11 megohms. At AC it is much lower and will still load the
> circuit you are testing.
>
> If you don't have one, get a Heathkit "Demodulator Probe", or an "RF Probe"
> for your IM-11. I can give you model numbers if you need them. I have seen
> those regularly on eBay for very little money, and for the sort of
> measuring
> you are doing, they are priceless.
>

I'm missing something that you're trying to convey.  I'm measuring DC,
so the 11 Megs should be OK.

>
> > I checked all resistances as per the schematic before power up and all
> > resistors were within tolerance (which, I must confess, surprised me).
>
> Most of us are probably not too surprised by that. However, I think most
> of us
> WOULD be surprised if all the fixed-capacitors are still OK...especially
> that
> can-type in the back.
>

The can-type is the back has been replaced with 3 separate units.  They are
tied together at
one end and soldered to a solder lug that I put in place of the can,  and
the other ends go to
the natural resting places of the original wires.


>
> > I provided measurements without drive just for some additional data
> > points.
>
> Never, ever do that. There are far safer, and more accurate, ways to obtain
> sufficient data.
>
> As Niel pointed out, without drive, the grid bias is next to nothing, and
> the
> tube will draw as much plate current as your power supply can provide.
>

OK Dad!  :-)  (humor intended......)

>
> This is, most definitely, NOT A GOOD THING!
>
>
> Kenneth G. Gordon W7EKB
>
> "Courage is being scared to death but saddling up anyway."--- John   Wayne
>
>