I have just got a Gould 465 DSO (same as 420 & 450 but 100MHz
bandwidth).

With the input grounded the trace is never dead straight (as with an
analogue scope) but exhibits a very, very tiny amount of vertical
noise. It doesn't alter with channel sensitivity and is the same on
both channels, so I'm guessing it's due to ADC error. Everything else
about the scope works perfectly.

It's livable with but if anyone can tell me whether this is normal
behaviour for these scopes (or other DSOs in general) I'd appreciate
it.

Bob

storan4wd wrote in message
oups.com...
I have just got a Gould 465 DSO (same as 420 & 450 but 100MHz
bandwidth).

With the input grounded the trace is never dead straight (as with an
analogue scope) but exhibits a very, very tiny amount of vertical
noise. It doesn't alter with channel sensitivity and is the same on
both channels, so I'm guessing it's due to ADC error. Everything else
about the scope works perfectly.

It's livable with but if anyone can tell me whether this is normal
behaviour for these scopes (or other DSOs in general) I'd appreciate
it.

Bob


If its invariant noise then surely it must be noise on the final "Y" stage
supply rail. Try adding a HV electrolytic to see if it has any effect.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"storan4wd" wrote in message
oups.com...
I have just got a Gould 465 DSO (same as 420 & 450 but 100MHz
bandwidth).

With the input grounded the trace is never dead straight (as with an
analogue scope) but exhibits a very, very tiny amount of vertical
noise. It doesn't alter with channel sensitivity and is the same on
both channels, so I'm guessing it's due to ADC error. Everything else
about the scope works perfectly.

It's livable with but if anyone can tell me whether this is normal
behaviour for these scopes (or other DSOs in general) I'd appreciate
it.

Yes, they seem to have those problems. Mine is a Tek and I wish I had never
purchased it.

On Aug 30, 10:06 pm, "N Cook" wrote:
storan4wd wrote in message

oups.com...

I have just got a Gould 465 DSO (same as 420 & 450 but 100MHz
bandwidth).

With the input grounded the trace is never dead straight (as with an
analogue scope) but exhibits a very, very tiny amount of vertical
noise. It doesn't alter with channel sensitivity and is the same on
both channels, so I'm guessing it's due to ADC error. Everything else
about the scope works perfectly.

It's livable with but if anyone can tell me whether this is normal
behaviour for these scopes (or other DSOs in general) I'd appreciate
it.

Bob

If its invariant noise then surely it must be noise on the final "Y" stage
supply rail. Try adding a HV electrolytic to see if it has any effect.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list onhttp://home.graffiti.net/diverse:graffiti.net/

Thank you for the suggestion, I see where you're coming from but
everything else on screen (menus, grid, measurements etc.) are all
rock solid. I therefore suspected that the problem did not lie in the
deflection system.

Bob

On Aug 30, 11:02 pm, "Charles" wrote:
"storan4wd" wrote in message

oups.com...

I have just got a Gould 465 DSO (same as 420 & 450 but 100MHz
bandwidth).

With the input grounded the trace is never dead straight (as with an
analogue scope) but exhibits a very, very tiny amount of vertical
noise. It doesn't alter with channel sensitivity and is the same on
both channels, so I'm guessing it's due to ADC error. Everything else
about the scope works perfectly.

It's livable with but if anyone can tell me whether this is normal
behaviour for these scopes (or other DSOs in general) I'd appreciate
it.

Yes, they seem to have those problems. Mine is a Tek and I wish I had never
purchased it.

Thank you Charles, now I can relax. If Teks do it it must be OK! Or
maybe we've both got faulty scopes?
Really appreciate your helping me.

Bob

Thank you Charles, now I can relax. If Teks do it it must be OK! Or
maybe we've both got faulty scopes?
Really appreciate your helping me.

You are most welcome.

I'll share a bit more. I retired and moved and had to convert to the
smaller stuff (I loved my old boat-anchor analog scopes). I wanted to
maintain some laboratory capabilities and thus purchased a TEK THS730A. It
works, but I really miss my analog scopes. I actually hate the damned thing
.... for the same reason you mentioned and others as well.

There are better digital scopes now available, but being retired (limited
income and lab space), I am sort of screwed.

Charles

... but being retired (limited
income and lab space), I am sort of screwed.


I'm with you all the way! It's better than working though!

Bob