HP 54601a voltage input question

[Tjj226_Angel]

Hello everyone.

I am trying to find an oscilloscope that can work with very high voltages (1Kv+). I work with a lot of vacuum tubes and I would like to be able to monitor tube tube plates to see the signal output.

I came across a HP/agilent 54601a for a good price. I read the manual and it says that it can handle 400v input. However the manual also states that it comes with 10:1 probes. I am trying to figure out if 400v is the maximum I can use with a 1:1 probe, or if it is the maximum I can use with the included 10:1 probe.

[0culus]

I'm not aware of any 'scopes that, without voltage dividers, handle that much on the front end. Personally, I'd use 10:1 or even 100:1 probes and protect the 'scope from seeing the full voltage. Better yet, for safety's sake, get a proper HV probing setup, e.g. https://www.tek.com/high-voltage-probe-single-ended

[rf-loop]

Hello everyone.

I am trying to find an oscilloscope that can work with very high voltages (1Kv+). I work with a lot of vacuum tubes and I would like to be able to monitor tube tube plates to see the signal output.

I came across a HP/agilent 54601a for a good price. I read the manual and it says that it can handle 400v input. However the manual also states that it comes with 10:1 probes. I am trying to figure out if 400v is the maximum I can use with a 1:1 probe, or if it is the maximum I can use with the included 10:1 probe.

Maximum input is 400V (DC + pk AC)
Input is oscilloscope front panel BNC connector.

Probe specifications are separate and Probe max voltages need read from probe specification.
When probe is set for 1:1 then 400V to probe tip is also level in oscilloscope input.

1:10 probe do not mean that you can connect 4000V DC to probe tip and then oscilloscope input level is again accepted 400V. Normal usual probe can not handle this level.
Then, also from probe data sheet need look carefully its max voltage but do not forget to read what is acceptable voltage level with higher frequencies.  Example: Some probe 1:10 may be specified for 600Vp-p but after some tens of kHz this may be lot of less, example with 100kHz it may be 200Vp-p and  1MHz it may be only 50Vp-p and so on.

But, when oscilloscope specification tell example 400V it means level between scope input BNC center tap and GND.  It need note of course that it also include peaks. So, example "dirty" 400V DC need be careful because it may include peaks what goes to over (undefined) damage level.

I have tested example Siglent scope inputs what are specified for 400VDC + pk AC). No problem at all with clean 400VDC. 

But, so or so, I do not still recommend it for use with 400Vdc even when it can last it without damage.
For more safe use  least 1kV 1:10 probe - depending situation. And for your needs least 2kV  1:100 probe what have also trusted safety, example Fluke and many others have some. (seriously, who can trust $10  100MHz 2kV  1:100 chinese elcheapo probe )

 HP54601A specs tell input BNC connector level.
www.testequipmenthq.com/datasheets/Agilent-54601A-Datasheet.pdf