Tek scope question

C

Chris Young

Guest
I finally got around to buying a scope yesterday (Tek 465B), and in
looking thru the specs in the manual, it states that the max input
voltage (for either DC or AC coupled) is 250Vp plus the peak AC voltage,
or 500Vpp.

I intend to use this in some upgrades to my tube preamp; I would like to
take a look at AC ripple off the filter caps in the PS sections, one
portion which is at 425Vdc, the other which is at 250-260Vdc or
thereabouts. I know the second one should be OK, but what about the
first?

When I was a tech, I didn't worry much about it, since it wasn't my
scope <g>. Now that it is, uhhh...

Thanks,

Chris

(remove the obvious to reply)
 
Chris Young wrote:
I finally got around to buying a scope yesterday (Tek 465B), and in
looking thru the specs in the manual, it states that the max input
voltage (for either DC or AC coupled) is 250Vp plus the peak AC voltage,
or 500Vpp.

I intend to use this in some upgrades to my tube preamp; I would like to
take a look at AC ripple off the filter caps in the PS sections, one
portion which is at 425Vdc, the other which is at 250-260Vdc or
thereabouts. I know the second one should be OK, but what about the
first?

When I was a tech, I didn't worry much about it, since it wasn't my
scope <g>. Now that it is, uhhh...

Thanks,

Chris

(remove the obvious to reply)
Click to expand...
As long as there is no ground loop (chassis of the preamp and chassis
of the scope), then the ground of a X10 probe is connected to the ground
of the PS (presume at chassis ground), and the probe tip goes to the
monitor point.
The probe rating, as i remember, is 500V; since it is dividing by 10,
that gives a maximum of 50V to the signal input connector - which has
its own rating.
There are special high voltage probes for monitoring signals in the KV
region, which may be useful on rare occasion.
 
My 465B book interprets it differently, it say 250V for the TOTAL of the DC
plus the peak AC, or 500 v P-P below 1kHz.

Don't be cheap, buy yourself some 10X probes and then all will be legal. You
can get decent probes new for about $35. Look at the Velleman or Pomona or
Probemaster probes, a step up would be PMK. If you work on tube stuff you
may want to consider getting a few 100X probes as well. The minimum
sensitivity of the 465B (without probes) is 5V/division, so, without probes,
you can display only 40 volts P-P on the screen. That is only about 12
VRMS, and you may well exceed that in some preamp and many power supply
situations.

However, for audio frequency work, you could just hook up an external series
capacitor to block the DC component. Likewise, for low frequency work, you
could improvise a 10X probe by putting a 9M resistor in series with the
input. Don't expect much accuracy above 5 kHz or so, however.


"Chris Young" <youngc1@comcast.net> wrote in message
news:3FF4E8EE.3915C051@comcast.net...
I finally got around to buying a scope yesterday (Tek 465B), and in
looking thru the specs in the manual, it states that the max input
voltage (for either DC or AC coupled) is 250Vp plus the peak AC voltage,
or 500Vpp.

I intend to use this in some upgrades to my tube preamp; I would like to
take a look at AC ripple off the filter caps in the PS sections, one
portion which is at 425Vdc, the other which is at 250-260Vdc or
thereabouts. I know the second one should be OK, but what about the
first?

When I was a tech, I didn't worry much about it, since it wasn't my
scope <g>. Now that it is, uhhh...

Thanks,

Chris

(remove the obvious to reply)
Click to expand...
 
Hi,

Thanks for the response. The scope came with two probes, P6105 and P6109 (I
believe). They are both x10 probes.

BFoelsch wrote:

My 465B book interprets it differently, it say 250V for the TOTAL of the DC
plus the peak AC, or 500 v P-P below 1kHz.

Don't be cheap, buy yourself some 10X probes and then all will be legal. You
can get decent probes new for about $35. Look at the Velleman or Pomona or
Probemaster probes, a step up would be PMK. If you work on tube stuff you
may want to consider getting a few 100X probes as well. The minimum
sensitivity of the 465B (without probes) is 5V/division, so, without probes,
you can display only 40 volts P-P on the screen. That is only about 12
VRMS, and you may well exceed that in some preamp and many power supply
situations.

However, for audio frequency work, you could just hook up an external series
capacitor to block the DC component. Likewise, for low frequency work, you
could improvise a 10X probe by putting a 9M resistor in series with the
input. Don't expect much accuracy above 5 kHz or so, however.

"Chris Young" <youngc1@comcast.net> wrote in message
news:3FF4E8EE.3915C051@comcast.net...
I finally got around to buying a scope yesterday (Tek 465B), and in
looking thru the specs in the manual, it states that the max input
voltage (for either DC or AC coupled) is 250Vp plus the peak AC voltage,
or 500Vpp.

I intend to use this in some upgrades to my tube preamp; I would like to
take a look at AC ripple off the filter caps in the PS sections, one
portion which is at 425Vdc, the other which is at 250-260Vdc or
thereabouts. I know the second one should be OK, but what about the
first?

When I was a tech, I didn't worry much about it, since it wasn't my
scope <g>. Now that it is, uhhh...

Thanks,

Chris

(remove the obvious to reply)
Click to expand...
 
On Fri, 02 Jan 2004 09:14:04 -0600, Chris Young wrote:

Hi,

Thanks for the response. The scope came with two probes, P6105 and P6109 (I
believe). They are both x10 probes.
Click to expand...
If you have x10 probes, the probe is likely the limiting factor. There is a
website somewhere which has a table of the tech details of all Tek probes.
Unfortenately I lost the URL, I seem to recall it was dedicated to old Tek
equipment.

Mat Nieuwenhoven
 
On Sat, 03 Jan 2004 21:54:39 +0100 (CET), Mat Nieuwenhoven wrote:

On Fri, 02 Jan 2004 09:14:04 -0600, Chris Young wrote:

Hi,

Thanks for the response. The scope came with two probes, P6105 and P6109 (I
believe). They are both x10 probes.

If you have x10 probes, the probe is likely the limiting factor. There is a
website somewhere which has a table of the tech details of all Tek probes.
Unfortenately I lost the URL, I seem to recall it was dedicated to old Tek
equipment.
Click to expand...
Not the site I was looking for but:
http://www.tek.com/site/ps/0,,60-15277-INTRO_EN,00.html
and
http://www.tek.com/site/ps/0,,60-15278-INTRO_EN,00.html

Mat Nieuwenhoven
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top