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Hi,
forgot to add:

in the Netherlands, Germany en Spain, they use wall sockets in a originally German model, meaning you can plug in both ways.

Devices are supposed to be designed so there is no difference no matter how you plug it in.

Eg in France they do use a keyed plug. The ground pin is the key.


Saludos,

Leo

On Wed, Feb 24, 2021 at 4:15 PM Stephen <stephen.nabet@...> wrote:

Exactly the same results...

If anything, the trace is cleaner, and what appeared to be a short line in
XY mode, now is clearly 2 sharp dots...

Hehe, so you've eliminated one possible cause. As we know "Once you
eliminate the impossible, whatever remains, no matter how improbable, must
be the truth".

I'm still concerned and/or confused by the weird voltage readings you got
from your outlet.

Hi,

Originally I'm Dutch, and in the Netherlands it's like this:

Live and neutral carry 230VAC between them.

At the powerplant the neutral is connected to a ground at the powerplant.

When the live and neutral arrive at a house, the house will have its own ground pin.

As a result there will be still 230VAC between Live and Neutral, and only a few volts between neutral and the local ground.

Now I live in Spain, and there it should be the same, however.....

I've seen situations where the Live and Neutral come from a local, nearby transformer and the power company "forgot" the ground the Neutral...

In that case you can see a proper ground, meaning low resistance between ground and eg. waterpipes, but..

If you have divided conbected that have RFI netfilters with capacitors between Live and the ground connection and between the Neutral and the ground connection these filters will "lift" that ground connection to about half the grid voltage.

So, there still might be a problem with the wiring in the house.

My 2 cents,

Leo

Maybe I’ll just go ahead and replace the 55V cap. I didn’t want to do that, because, as you all know, these things are a pain to replace. At least they are for me...
Maybe also replace the X safety cap in the process...

On Wed, Feb 24, 2021 at 10:07 AM, Siggi wrote:

Interesting, I can't explain why this would be.
For giggles try and plug the scope into the bathroom outlet and see whether
the noise goes away?

Yep, I just did that... See my last post.

I moved the scope to the bathroom and tested it on a ??better?? outlet, and guess what...
.
.
.
Exactly the same results...

If anything, the trace is cleaner, and what appeared to be a short line in XY mode, now is clearly 2 sharp dots...

Francesco and Michael,

Measure the heater voltage first. If low, go to the second paragraph. If you know it sat a long time before you started using it, read below.

You scopes might have been sitting unused for some time, usually some years, and the crt will look weak when it is not. I have done this to TVs many times by removing the socket and putting a CRT checker on it, raising the heater voltage to about 7-8V for 10-30 minutes. That "cracks" the cathode. I was told by TV techs that a crt that sits for a long time unused will do this, new or used and that raising the heater voltage for a short time helps remove gas. I do not know how it get gas that way when it is still good. After the time is up, the original socket was put back on the end, unit powered up and it looked fine. If a checker was used to test it, it showed in the good region.I do run heaters of crts that have not been on for a long time before powering the unit up to make sure the screen lights up properly. Usually the heater is run at the regular voltage for some time, e.g. 30 minutes. I know that some transmitting tubes that have sat for some time need their heater/filament run for a while before any B+ is applied. Those are run at the rated heating voltage.

Another thing that will cause the problems you two have is the heater voltage is too low. Check the heater voltage where it goes to the socket. It should be 6,3V. The resistor from the heater winding could be high causing the heater voltage to be too low. Usually if the high voltage is right then the heater voltage is right. The meter used here should be a good VOM or DVM that will respond to the frequency of the oscillator circuit. I use my Simpson 260 for this test. If the heater reads 6,2 or 6,4V, that is close enough. Something like <6V or 6,9V is too far off. These heaters are 60mA so use Ohm's Law if needed to adjust the resistor value if necessary to change.

Mark

On Wed, Feb 24, 2021 at 3:51 PM Stephen <stephen.nabet@...> wrote:

On Wed, Feb 24, 2021 at 09:19 AM, Siggi wrote:

This means you know ONE outlet in your house is definitely grounded. What
is the AC voltage you measure from live/neutral to ground in that outlet?

What I meant is that I tested all the sockets in the house, with several
extended cables, against this pipe and the ground lug in the bathroom, and
they are ALL properly grounded. They all pass the continuity test.

HOWEVER, I found out that, unlike the other sockets in the house, the one
in the bathroom read 0.003VAC between Neutral and Ground, and 233VAC
between Hot and Ground and/or Hot and Neutral. BIG DIFFERENCE in wiring,
apparently...

Interesting, I can't explain why this would be.
For giggles try and plug the scope into the bathroom outlet and see whether
the noise goes away?

Hi Steven,

Very interesting and thoughtful approach. Will definitely test that as well.

Thank you.

On Wed, Feb 24, 2021 at 09:19 AM, Siggi wrote:

This means you know ONE outlet in your house is definitely grounded. What
is the AC voltage you measure from live/neutral to ground in that outlet?

What I meant is that I tested all the sockets in the house, with several extended cables, against this pipe and the ground lug in the bathroom, and they are ALL properly grounded. They all pass the continuity test.

HOWEVER, I found out that, unlike the other sockets in the house, the one in the bathroom read 0.003VAC between Neutral and Ground, and 233VAC between Hot and Ground and/or Hot and Neutral. BIG DIFFERENCE in wiring, apparently...

Hmmmm

Hi, All - this has been an interesting thread, but no resolution (yet).

I am neither an EE nor licensed in EU or Europe voltages. While I don’t have any 465B or 466 scopes, I have several 2445 sets that need repairs, and as a technician, having read this thread, a few things come to mind...

First, whatever leads are on your DMM, short them, and measure the baseline resistance (like 0.2 ohm).

1) I believe most Tek Scopes have 3 wires leading to an AC 3 prong plug or a NEMA Socket and plug-in cord. With the problematic 465B scope unplugged, measure the R between each pin from the AC Plug to a convenient internal point inside the scope, if a factory attached wire, effectively measuring the conductor end to end. Mark these numbers down.

2) Measure the same thing on the 466 scope that also may have a problem, write those numbers down.

3) Now, measure the same three things on one or two of the other scopes that does not have the problem.

This could find a bad line cord, shorting X Cap, bad connection to ground lug, etc. Physically move the wire around at both ends to see if the readings deviate. Any deviations or major differences?

4) If there is a line filter after the line cord, inside the various scopes, take readings again on the 465B, 466, and a good scope, also check the line filter for smell, or variations in R readings, on the input and the output after the line filter. Any noticeable Differences between the sets?

I once had an amplifier where from the AC plug to a point inside the amp, the R reading was >>100 ohms! It should be more like < 0.2 ohm on a properly working line cord, or ~ 0.1 ohm on a 14 gauge Line Cord.

Maybe something useful will show up from these readings, also visually inspect the X-caps on the PS Board inside the scope (if any).

Steven

Jean-Paul wrote:

Here is a set of two like new with all access, that I just found on epay, $199 the pair:

There are no pictures of the probe tips without the witches hats, so I would assume the worst (that the tips are busted).

I would stay away from this sale unless I were in the market for specific parts (that we can see are included and undamaged). It would be a lot to pay for two compensation boxes, a pair of witches hats, and assorted bits (though the witches hats for the subminiature probes are a bit hard to come by, they're not worth $100 each).

-- Jeff Dutky

Siggi wrote:

This means you know ONE outlet in your house is definitely grounded.

Also, grounding the outlets in the bathroom is probably the highest priority for any construction company, so even if they did a terrible job on every other outlet in the residence you might expect that the bathroom outlet would be done properly (or, at least, that the ground would be correct. There's still a question of hot and neutral being right).

-- Jeff Dutky

On Wed, Feb 24, 2021 at 3:10 PM Stephen <stephen.nabet@...> wrote:

I have tested the voltage between a water pipe and the ground lug in my
bathroom. 0.007VAC. And, as expected, the two pass the continuity test.
All the ground lugs are connected as well.
They are tied to earth. Can we now say this ground thing is a non-issue?
Or am I missing something...?

This means you know ONE outlet in your house is definitely grounded. What
is the AC voltage you measure from live/neutral to ground in that outlet?

I have tested the voltage between a water pipe and the ground lug in my bathroom. 0.007VAC. And, as expected, the two pass the continuity test.
All the ground lugs are connected as well.
They are tied to earth. Can we now say this ground thing is a non-issue? Or am I missing something...?

On Wed, Feb 24, 2021 at 12:11 PM Stephen <stephen.nabet@...> wrote:

But it doesn’t explain why none of my other scopes do that...
If the outlets were the problem (and I’m not saying they’re not),
shouldn’t all my scopes show that same behavior?

It's undefined behavior. Some scopes may incidentally be better protected
from noise infiltration under these circumstances than others. There are
scopes that have known noise issues when grounding is poor, screws are
loose, etc, and I believe the 465B is one of those. I don't own one,
though, so I haven't followed the threads here that closely.

This is also all speculation still, though the facts fit the hypothesis so
far.

Can you carry the scope over to your kitchen or bathroom and plug it in
there, see whether the noise goes away?

On Wed, Feb 24, 2021 at 10:25 AM, Jean-Paul wrote:

Here is a set of two like new with all access, that I just found on epay, $199
the pair:

But the seller clearly states, in both the ad's header, and in the item's description... that "Condition:For parts or not working."
And the definition of that on Ebay is,

An item that does not function as intended and is not fully operational. This includes items that are defective in ways that render them difficult to use, items that require service or repair, or items missing essential components. See the seller's listing for full details.

That means the seller is telling one "up front" that they are not working. And if they don't work... then the seller already told one that.
Does anyone think that the seller should give one's money back, if one purchases these non-working probes, because they actually don't work?
Give to charity.

Folks,My 7104 behaves the same way.? I don't use it daily, and have put off examining it until I have more time. I am eager to find out if there was a cause on your scope.Regards,Mike
On Wed, Feb 24, 2021 at 11:27 AM, Francesco Franzini<franzini.francesco@...> wrote: Following your advices i double checked everything, replacing resistors out of spec and checking carefully capacitors, transistors and IC's with no improvement, after a lot of power on/power off cycles i noticed that suddenly the crt regained right focus and astigmatism without any logic or correlation with anything, thinking about it i left the oscilloscope powered on for 48 hours with no readout and zero intensity (nothing on the crt screen).

After the "treatment" everything is working as expected, no loss of focus or astigmatism, trace and readout very sharp and bright.

I really have no idea on what was wrong on my 7104 but my findings seems to point to the crt, i hope the experts on this forum can have better explanation on this issue.

Thank you for your support and help

Francesco

My experience assembling a set of P6131s for my 2465DMS may be illustrative: I was able to put together 4 good probes, along with some spare parts, from eBay purchases of several lots of random accessories and six or seven used probes. Damaged tips are very common, and I don't know how to repair them (or if that is even possible). I managed to scrounge four good tips from the used probes, and also found a partial set of new tips in a collection of random accessories.

The subminiature modular probes appear to be very fragile, and also in some high demand. Finding older (and slower) probes (e.g. P6075 or P6106 200 MHz and 250 MHz probes for the 475 and 475A, or P6121 100 MHz probes for the 2236).

I have also had pretty good luck with the cheap Chinese probes, at least the lower bandwidth ones (I have a pair of 100 MHz probes that I use for the 2200-series scopes, and a pair of 200 MHz probes for the 475. Both sets were bought from Amazon, and seem to be of good quality). If I were going to get third part probes for a faster scope I would consider buying directly from Probe Master (nice probes with readout actuator pins, and the prices are not outrageous). None of the Chinese probes I've seen on Amazon have a readout actuator pin, so there are compromises.

I should really go back and test the Chinese probes again, now that I have a better understanding of how to measure the bandwidth (and better tools to do so). My impression, as of this past fall, was that the 200 MHz probes were performing just about as well as the Tek P6075s, but I don't have quantitative measures to back that feeling up.

-- Jeff Dutky

On Wed, Feb 24, 2021 at 08:07 PM, Roy Thistle wrote:

So far, I believe that Tektronix is the leader in passive probes.

I have lots of high-end Tek passive (and active) probes, including P6137, -38, and -39A/B. Very nice but not without competition. Have a look at Picotech's P2056 as an example. Measuring them (@25 Ohm source impedance, as it should be done) shows there's not much between them and the handling of the very small body and very sharp pin for e.g. SMT is excellent. Not better than Tek per se but there's more in the Tek league. BTW, LeCroy use them...

Raymond