"robb" wrote in message
...

"Arfa Daily" wrote in message
...

"robb" wrote in message
...
Silicon cured, CRT installed and tested.
Sorry no fireworks or shooting flames

Problems:
==========
The display is skewed and the intensity and focus are off.
I was not expecting te new CRT to have hyper-intensity
troubles.
That is... from no visible trace to oversaturated CRT
brightness
is a very small range of knob motion maybe a 1/4-1/3 of he
full
turn .
And the focus is very sensitive, touch sensitive ? was not
before.

It sounds to me like this replacement CRT might not be quite as
'compatible'
as you had hoped ... :-( Maybe that's part of the reason that
the PDA lead
was not long enough to fit in your chassis i.e. to stop such a
substitution
taking place. As far as the trace being 'skewed' do you mean
that it is not
perfectly horizontal, or that it is trapezoidally distorted ?
If the former,
then most decent 'scopes have a trace rotation control
somewhere. As far as
the brightness / focus issues go, that is likely to be quite
difficult to
resolve, and will probably require changes to be made to the
component
values in the resistor chains providing the biasing voltages to
the various
electrodes. I would suggest that you will not get too far with
that, without
having schematics for both the 'scope that you've put the tube
in, and the
one that it came out of, so that you can make comparisons of
values and
expected voltages. Just as a matter of interest, are the quoted
deflection
sensitivities for both tubes the same ?

Good luck with it - I think you'ree going to need it, but it's
nice to see
that a sense of experimentation still exists out there - it's
the sort of
thing that I would have been playing with 30 years ago ...


Hello Arfa,
It is a Tek scope.
There are lots of pots for adjusting the CRT params.

The CRT was replaced with its **reverse** compatible replacement
P/N.

That is, typically one replaces the earlier model CRT with the
newer model and i have done the reverse. I replaced the newer
model with the earlier model. Unless it was a "one way
compatibility" then technically it should work.

The HV lead was longer in newer models because of physical change
to the Flyback/HV multiplier transformer and orientation. The
earlier model machines had an HV Jack on an 3" HV lead coming off
the Flyback the newer models have te HV Jack on the Flyback
directly.

So you need just 1" (2.5 cm) more HV lead to make it there.

Hopefully i can cure problems with the adjustments, as I do not
really want to modify the original PCB /schematic values.

Thanks for help and ideas Arfa,
robb

Hmmmm. Sometimes, compatible substitution *is* a one-way street. If the
parameters of the two tubes were sufficiently similar, I would not have
expected there to be a huge difference in the external setups, or for the
operation of the user controls to become 'bunched' as you described. There
are a couple of Tek 'scope experts who pop up on here from time to time who
would be much better qualified to advise you on the specifics of your
problems than I, so hopefully one of them will dive in to help you shortly !

Arfa