[sdiy] Old 20Mhz scope high on LSD!!

[harrybissell]

KD on LSD ???    :^P

Of course you are correct... there are a few problems

1) The phosphor of the scope tube will have been selected for the sweep
speed.  Higher sweep rates will need a shorter persistance phosphor, and

a lot higher acceleration voltage for the tube.

2)  The high voltage deflection amps need to be beefed up to handle the
faster signals, at high voltages.

3) Damping everything properly will be tough, stray capacitances that
were
not designed out of the chassis will come to haunt you in spooky LSD way
:^P

One possible solution would be
to build a digital sampling front end and use the slow scope to read out
the
results.

I would recommend finding a broken scope of high bandwidth and restoring
it if you
really want to play. Jim Williams (of Linear Technology) restores old
Tektronix
scopes like some people restore cars

H^) harry

karl dalen wrote:

> Hi!
>
> What about upgrading your old scope?
>
> I have a old 20Mhz scope im thinking to update a bit.
> Since almost all CRT tubes have a Bw of several hundred Mhz it
> would be quite easy to upgrade the input amp's and the time base,
> ( basically extend or change the capacitors in the ramp generator.)
> My scope is quite old early 80'es so the input amps uses LM3046
> array, today when we have Jfet OP amps easily doing 300Mhz
> things becomes in a different light.
>
> Lets say a DC 100-150Mhz total Bw without changing to much
> of the internal circuit would be possible! That would not be
> baad for an old farty 20Mhz scope!
>
>
> Has anyone been doing this lately? Whats your results?
>
> Otherwhise, coments are wellcume!
>
> Regards
> KD