Hi all,
I just got my Tektronix 2213A its rated for 400V pk - pk, I buy it to take mesurement on my tube amp project. But I got around 425V on my psu, if I scope this, will I kill it ? What can I do ? I got right now a 10x probe tek 6121, does it exist a 20x or a 25x to take such mesurement ? Thank in advance
I just got my Tektronix 2213A its rated for 400V pk - pk, I buy it to take mesurement on my tube amp project. But I got around 425V on my psu, if I scope this, will I kill it ? What can I do ? I got right now a 10x probe tek 6121, does it exist a 20x or a 25x to take such mesurement ? Thank in advance
Hi guitvinny,
High voltage probes are available. They are generally 100:1. You must start at the highest V/div range even when on AC. Please always do this or you may damage the input circuit.
If you kill your 'scope (hope not!) I may need the knobs
I try to use older (non-IC front end) type scopes when working with tube amps. They can take a little more abuse and survive. They are also repairable whereas the IC types are not generally. Tek stopped supporting your model around 11 years ago I think (like mine).
-Chris
High voltage probes are available. They are generally 100:1. You must start at the highest V/div range even when on AC. Please always do this or you may damage the input circuit.
If you kill your 'scope (hope not!) I may need the knobs
I try to use older (non-IC front end) type scopes when working with tube amps. They can take a little more abuse and survive. They are also repairable whereas the IC types are not generally. Tek stopped supporting your model around 11 years ago I think (like mine).
-Chris
The attenuation is done on the probe, so only 1/10th or 1/100th of the measured voltage will be fed to the input of the oscilloscope as long as the probe attenuator is not overstressed causing insulation breakdown.
The inputs of mine are also rated at "400V max." and my 1x/10x standard probes are rated at 600V peak, but I don't feel like testing these ratings
The inputs of mine are also rated at "400V max." and my 1x/10x standard probes are rated at 600V peak, but I don't feel like testing these ratings
Anatech, you have email about the knobs.
Guitvinny, almost any recent multimeter will do a good job of measuring 400+ Volts AC or DC directly. I would use one before risking an oscilloscope. Even a very inexpensive meter would be good enough to get an idea of what is happening in your circruit.
Guitvinny, almost any recent multimeter will do a good job of measuring 400+ Volts AC or DC directly. I would use one before risking an oscilloscope. Even a very inexpensive meter would be good enough to get an idea of what is happening in your circruit.
GV,
Got some ideas for ya.
Ive got a 2235 here and it has a warning not to put more than 400vdc when using AC coupling. Couple that with a p to p and your running into dangerous ground. That coupling cap can break down and psssssssst there goes your front end.
Tek did make a 100 to 1 probe, but it was expensive and hard to use.
Another way to do this is...
If you have Tek P6122 probe for example they read
10M ohm
11.0pf
10x
If you hang a 100m ohm resistor in front of the probe, that will give you a rough 10 to 1 divider, using the internal resistance of the existing probe. It's cheezey but it works.
The other trick is not to measure the high voltage directly but use you output transformer's output and see if that's proper. It might save you some expensive parts.
Also what Mr Stocker said about standard multi meters.
On the old Simpson 260's (remember them) there is an 'output' jack that has a dc blocking cap in line with the measurment element, so you see just the AC part of the signal. Read the manual and learn how to use this feature. It's been 20 + years since I last calibrated one so memmory can be a touch fuzzy.
One last idea, make a small coil and wrap it around the high voltage line (well insulated). Then feed your scope the output from that coil. The scaling might be screwey but you will get an idea what the wave is doing.
I presume your looking for cliping p/s sag and other such problems.
Much luck
Jack Crow in Kuwait
Got some ideas for ya.
Ive got a 2235 here and it has a warning not to put more than 400vdc when using AC coupling. Couple that with a p to p and your running into dangerous ground. That coupling cap can break down and psssssssst there goes your front end.
Tek did make a 100 to 1 probe, but it was expensive and hard to use.
Another way to do this is...
If you have Tek P6122 probe for example they read
10M ohm
11.0pf
10x
If you hang a 100m ohm resistor in front of the probe, that will give you a rough 10 to 1 divider, using the internal resistance of the existing probe. It's cheezey but it works.
The other trick is not to measure the high voltage directly but use you output transformer's output and see if that's proper. It might save you some expensive parts.
Also what Mr Stocker said about standard multi meters.
On the old Simpson 260's (remember them) there is an 'output' jack that has a dc blocking cap in line with the measurment element, so you see just the AC part of the signal. Read the manual and learn how to use this feature. It's been 20 + years since I last calibrated one so memmory can be a touch fuzzy.
One last idea, make a small coil and wrap it around the high voltage line (well insulated). Then feed your scope the output from that coil. The scaling might be screwey but you will get an idea what the wave is doing.
I presume your looking for cliping p/s sag and other such problems.
Much luck
Jack Crow in Kuwait
Eva said:
The inputs of mine are also rated at "400V max." and my 1x/10x standard probes are rated at 600V peak, but I don't feel like testing these ratings
I commonly use standard x10 probes on TV line output stages, and have done for a number of decades - I've had perhaps two probes die in all that time, but only after years of use. With the scope on 10V/cm and a x10 probe, the pulses are greater than the screen height, around 1000V at 15,625Hz.
Another reason NOT to use Tek scopes, generally their highest range is only 5V/cm! - at least on the ones I've seen and tested.
Carrying on from a point someone else mentioned, there's generally very little use for a scope in valve amplifiers anyway, a simple cheap meter does almost anything you need.
Eva said:In a TV line stage you don't even have to touch the circuit with the probe tip, just place it closer to the switching nodes and you will see all the waveforms
A loop antenna made by connecting the ground lead to the tip of the probe also allows to see TV switching waveforms
It might allow you to see they exist, it doesn't allow you to see what they really look like, or measure their amplitude.
hehehGV,
Ive been 'doing' high power analog electronics now for 27 some odd years.
I don't think Ive ever had a blown out 100Meg ohm resistor.
A rare 10Meg (Oxygen got it.)
A few 1 Meg's (Again oxygen, and mechanical dammage)
A whole pile of 100k's (from computer monitors)
Think about the voltage it takes to get a 1/4 watt of heat in series
with a 100 meg's of ohms.
To quote Mr. Rodgers "Can you say 'flash over'? Sure you can!"
Good luck and be safe
Jack Crow in Kuwait
Ive been 'doing' high power analog electronics now for 27 some odd years.
I don't think Ive ever had a blown out 100Meg ohm resistor.
A rare 10Meg (Oxygen got it.)
A few 1 Meg's (Again oxygen, and mechanical dammage)
A whole pile of 100k's (from computer monitors)
Think about the voltage it takes to get a 1/4 watt of heat in series
with a 100 meg's of ohms.
To quote Mr. Rodgers "Can you say 'flash over'? Sure you can!"
Good luck and be safe
Jack Crow in Kuwait
An X10 probe is essentially a 9 meg resistor with a small capacitor across it. At the scope end of the cable a variable cap sets the high frequency attenuation in conjunction with the scope's input capacitance. Low frequency attenuation is accomplished by the scope's 1 megohm input resistance. (There are other RC networks that tweek out parasitics from the cable.)
A scope's input usually has switched attenuators between the input jack and the actual active input amplifier. These attenuators maintain the input resistance and capacitance (and bandwidth) to very tight limits.
When the scope's input coupling is set to AC, the capacitor is inserted between the scope's input jack and the input attenuators. So that capacitor sees all the DC at the probe tip through the 9 megohm resistor. When the scope is set to DC coupling, the scope only sees 1/10th the voltage at the probe tip. When the scope's input coupling is set to GND, the input to the attenuators is grounded but a dummy 1 Meg resistor is connected to the attenuator side of the AC coupling capacitor. This allows the cap to charge or discharge without that voltage spike going to the input circuitry.
The above applies to Tektronix scopes of the general purpose variety with 1 megohm inputs. It does not apply to ultra high bandwidth or sampling input scopes or 50 ohm inputs. For other brands, YMMV.
A scope's input usually has switched attenuators between the input jack and the actual active input amplifier. These attenuators maintain the input resistance and capacitance (and bandwidth) to very tight limits.
When the scope's input coupling is set to AC, the capacitor is inserted between the scope's input jack and the input attenuators. So that capacitor sees all the DC at the probe tip through the 9 megohm resistor. When the scope is set to DC coupling, the scope only sees 1/10th the voltage at the probe tip. When the scope's input coupling is set to GND, the input to the attenuators is grounded but a dummy 1 Meg resistor is connected to the attenuator side of the AC coupling capacitor. This allows the cap to charge or discharge without that voltage spike going to the input circuitry.
The above applies to Tektronix scopes of the general purpose variety with 1 megohm inputs. It does not apply to ultra high bandwidth or sampling input scopes or 50 ohm inputs. For other brands, YMMV.
The input cap is rated for 400V DC so with a 1X or 10X probe you should not go past 400V. However this 100MHz 4000V 4KV High Voltage Oscilloscope Clip Probe X100 w Alligator Clip New | eBay is an example of what will work. It has a resistive attenuator inside, before you get to the scope. At $50 its a bargain. The Tek equivalent I have were more like $1K new. I would definatey invest in one for HV work. The older Tek probes were also fine at those voltages but the new ones are probably better and safer. BE SURE TO CONNECT THE GROUND CLIP!!!! or the divider doesn't help and your scope chassis could be at the HV potential.
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