Hi.
Its been a while since I have worked on valve gear. I was wondering if someone could clear out something for me. I have a Tektronix 453 Scope, as well as a Rigol DS1102E scope.
Can I probe those 250V-550V DC Valve- plate pins if I set my probes to x10 and the scope to AC coupling????
If not, how would I go about doing so?
Its been a while since I have worked on valve gear. I was wondering if someone could clear out something for me. I have a Tektronix 453 Scope, as well as a Rigol DS1102E scope.
Can I probe those 250V-550V DC Valve- plate pins if I set my probes to x10 and the scope to AC coupling????
If not, how would I go about doing so?
the user manual should be able to fill you in on this.
but yes please do wait for an experienced reply from people more experienced people. or go here: www.syscompdesign.com/AppNotes/probes.pdf
I too would like to know this answer in relation to tube rectifiers and oscilloscopes.
this might help: www.diyaudio.com/forums/tubes-valves/65347-how-do-you-measure-ripple-b.html
but yes please do wait for an experienced reply from people more experienced people. or go here: www.syscompdesign.com/AppNotes/probes.pdf
I too would like to know this answer in relation to tube rectifiers and oscilloscopes.
this might help: www.diyaudio.com/forums/tubes-valves/65347-how-do-you-measure-ripple-b.html
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It does not make sense and it is dangerous for the scope and for you. The usual spec is 250V for a 10:1 probe. Why do you want to measure the AC on the anode? Measure the B+ with a DMM, and measure the AC at the secondary of the OT. Or measure the anode AC and DC current by inserting a 10 ohm resistor between the cathode and GND.
Most x10 probes have typical voltage ratings in the 400 to 600V.
However, you have to be careful with the AC coupling: the input blocking cap of the scope will see the full DC voltage, irrespective of the presence or not of a x10 probe.
The rating of the scope input is generally lower, more like 250V.
The 40 Meg impedance ones include an additional resistor in the foot of the divider, and are safe with capacitive coupling.
The 100 Meg aren't:
Example:
High Voltage Probe Passive High-voltage Probes | Tektronix
Seems some people are using high voltage probes and others are not, what is really needed in assessing a tube amp? I could use a little education on this too. Thanks!
Most decent 'scopes have the max Vp-p printed by the Y [vert] amp BNC sockets. Take note and do not exceed this. X100 probes are available but not common. Don't forget the BNC outer and probe ground clip are connected to ground so don't try and "float" a scope to make differential measurements by disconnecting the mains earth connection.
Last week I was working on the instrumentation protection circuit which Supertex shows on Application Note D-11 -- using a pair of LND150 depletion MOSFETs back to back -- one pair is good for 500V of protection.
I've found that the appropriate resistor value has to be determined by trial and error since the characteristics of the devices are quite variable. (You can, of course measure the pinch off voltage and Idss to come up with a very close approximation.)
The whole thing won't cost you more than $2. They come in a TO-92 package which is plenty compact. It simulates quite well, seems to work well on the bench.
http://www.supertex.com/pdf/app_notes/AN-D11.pdf
I've found that the appropriate resistor value has to be determined by trial and error since the characteristics of the devices are quite variable. (You can, of course measure the pinch off voltage and Idss to come up with a very close approximation.)
The whole thing won't cost you more than $2. They come in a TO-92 package which is plenty compact. It simulates quite well, seems to work well on the bench.
http://www.supertex.com/pdf/app_notes/AN-D11.pdf
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