On Mon, Mar 4, 2013 at 8:11 AM, <tubesnthings@...> wrote:

ugly and wayyy overpriced - but interesting!
english lettering....
Bernd

I think we have discussed these before... they were not Polish... they
were made by EMG in Hungary:

If your 40A is at line frequency or SMPS frequencies like 20-100 kHz, it should be no problem - the linearity and accuracy will suffer, but there shouldn't be much power dissipation when occasionally exceeding the specs.

Of course, there must be some current/frequency level that will cause damage due to overheating the secondary windings or the core, making things melt. The frequency will be most important since it causes the power induction. Picture the situation at DC - no matter how much current you shove through the link, the core will saturate, so no more signal will be induced into the secondary windings. Only the power dissipation in the link itself can generate enough heat to melt things around it. The Hall elements on DC probes are also protected by core saturation.

As frequency goes up, the problem becomes heat from the power dissipation in the windings and from core loss. When the frequency gets high enough, the core doesn't matter any more - everything will heat up from the RF current. Also, single pulses that are extremely large can damage things - but that's true with anything.

Ed

On 3/4/2013 11:48 AM, Alex wrote:

I think we all know intuitively what happens if a voltage rating is
exceeded on a probe or just in general: Bzzt and maybe poof!

But what happens if you exceed the current rating of a P6042? It's rated
at 20A up to 1MHz, I'm working on a project with a 40A rectifier.

Will there be permanent damage to the probe? (If I can even get 40A
through a wire small enough to fit the probe).

I'll probably end up using a shunt but it might still be possible to get
a malfunction current way higher than 40A at the start of this project.

Hello--

It's possible that running a current probe over its rating would
result in semipermanent magnetism of the core. You'd then need to demagnetize the core by running gradually-decreasing AC
through it (thinking of a filament transformer w/a resistive load
fed from a Variac). I've never encountered the problem,
so I'm hoping that someone else will comment.

You can fake a current shunt by connecting several wires of
equal length in parallel. Clamp onto one wire and measure
the current. Then multiply the measurement by the number
of wires in the bundle.

73--

Brad AA1IP

I think we all know intuitively what happens if a voltage rating is exceeded on a probe or just in general: Bzzt and maybe poof!

But what happens if you exceed the current rating of a P6042? It's rated at 20A up to 1MHz, I'm working on a project with a 40A rectifier.

Will there be permanent damage to the probe? (If I can even get 40A through a wire small enough to fit the probe).

I'll probably end up using a shunt but it might still be possible to get a malfunction current way higher than 40A at the start of this project.

--- In TekScopes@..., Roland Manser <roland.manser@...> wrote:

Bought a 310A for little money, in perfect condition, optically and
electrically (what a sharp trace!), lucky me.

2 Questions:

It has serial number 013491, rectifier is with silicon diodes.
Anybody has an idea on which year this little oven was built?

Currently the transformer is wired for the "middle" tap. When I measure
my line voltage, it is 230V, with very little variation. Would it make
sense to wire the scope for 240V, to reduce voltage and heat stress?


Roland

This scope model was in production for well over a decade. As mentioned several times in this forum, there is no direct way to determine production date from serial number. These records were never centralized or maintained within Tek. The best way to determine when yours might have been built is to look at the date codes on the electrolytic caps. It is safe to assume that Tek did not carry the inventory long for a higher runner like this, so the scope was probably made within four months or so of the date code.

I have found the filter caps in the 310A to be well over the size needed for maintaining regulation on low line conditions. That probably explains that why the four that I have owned all functioned perfectly with the original caps, being nearly 50 years old. If your nominal line voltage is in the high range, I would try switching to the higher tap. If you have a variac, you could test this first before you make the mod by setting it to the low end of the current range, then measuring the ripple valley of the filter caps to see home much headroom the regulators have. This measurement is easier if you have a differential comparator plug in such as a type W or 7A13.

Steve

Sorry yes its voltage. Its for testing the high voltage regulator in a 475. I cannot afford another meter or a $100 probe. The voltage divider idea may work.

开云体育

ugly and wayyy overpriced - but interesting!

english lettering....

Bernd

?

开云体育

It's the same size as the 80K-40, yellow instead of red, has the same 1 GOhm
input impedance when used with a 10 MOhm input meter, but rated only for 15
KV instead of 40 KV.

I don't really see why an 80K-40 wouldn't be useful in the same application
that the 80K-15 was made for. Or perhaps the 80K-40 came later with higher
rated insulation to 40 KV?

Joe

On 03/04/2013 07:35 AM, Bert Haskins wrote:

On 03/04/2013 05:24 AM, Mark Wendt wrote:

On 03/04/2013 01:13 AM, David wrote:

Fluke 80K-6 high voltage probes are inexpensive used and good to 6
kilovolts. They are designed to be used with a 10 megohm input
resistance multimeter which is standard. They only have 75 megohms of
input resistance though which may be a problem measuring many of the
CRT voltages like the grid or focus but will work fine for measuring
the cathode voltage which is regulated.

I knew probes could be used for a lot of things, but this is a new one
on me:

<>

Mark

No surprise, electrostatics can go to some pretty high voltages.

They can give you a nasty bite.

I'd never seen it called an Electronic Air Cleaner probe before. ;-)

Mark

On 03/04/2013 05:24 AM, Mark Wendt wrote:

On 03/04/2013 01:13 AM, David wrote:

Fluke 80K-6 high voltage probes are inexpensive used and good to 6
kilovolts. They are designed to be used with a 10 megohm input
resistance multimeter which is standard. They only have 75 megohms of
input resistance though which may be a problem measuring many of the
CRT voltages like the grid or focus but will work fine for measuring
the cathode voltage which is regulated.

I knew probes could be used for a lot of things, but this is a new one
on me:

<>

Mark

No surprise, electrostatics can go to some pretty high voltages.

They can give you a nasty bite.


settings online go to:

On 03/04/2013 01:13 AM, David wrote:

Fluke 80K-6 high voltage probes are inexpensive used and good to 6
kilovolts. They are designed to be used with a 10 megohm input
resistance multimeter which is standard. They only have 75 megohms of
input resistance though which may be a problem measuring many of the
CRT voltages like the grid or focus but will work fine for measuring
the cathode voltage which is regulated.

I knew probes could be used for a lot of things, but this is a new one on me:

<>

Mark

Hello Raymond

Fluke 80K-6 high voltage probes are inexpensive used and good to 6
kilovolts. They are designed to be used with a 10 megohm input
resistance multimeter which is standard. They only have 75 megohms of
input resistance though which may be a problem measuring many of the
CRT voltages like the grid or focus but will work fine for measuring
the cathode voltage which is regulated.

On Mon, 04 Mar 2013 04:41:16 -0000, "anson_williams@..."
<tractormananson@...> wrote:

Is there a way to take this reading without a 3k meter?

Is there a way to take this reading without a 3k meter?

I had a similar problem recently with Aerovox caps in my 564: one of these was defective, causing malfunction when erasing the storage screen.
After some checks, the only culprit was a 0.1uF 600V Aerovox capacitor. I don't have any ESR meter, but examining the erasure pulse with another scope, I immediately realized that the capacitor was lossy. I think ESR was fine, buth the dielectric absorption not.

On the component list, the caps was specified as metallized polyester.
I've temporarily replaced the defective one with two capacitor 0.1uF 630V ceramic FACON in parallel to compensate for major losses in ceramic type, waiting to have the right polyester type.

Oddly enough, since Matt states that only 549 Portland scopes used Areovox caps, my 564 is from Heerenveen, Netherlands.

Max

The 7503 needs work on the plug-in connectors. The side covers of the connectors need to be replaced. (This is a common failure mode and has been discussed in this forum.) I believe the scope is otherwise fine.

The TM506 works, but the power supply capacitors need to be replaced. It works with low-power plug-ins as is. Power-hungry plug-ins cause the DC supply to have unacceptable ripple, due to the bad capacitors.

The RM564, if I recall correctly, works in non-storage mode, but not in storage mode. I can check that. (I haven't powered it up in years.)

None of these items comes with plug-ins.

These items are available for local pickup in Manhattan, free of charge. Email me off-list if interested. thanks, -Kurt