Another approach to containing metal chips when drilling is to use a
putty-like material to catch the metal shavings.  The putty-like
material can be packed on the drill side of the sheet metal (either as a
toroid, which would allow for visual confirmation of the target hole
location, or on the "backside", as a "blob" to catch the shavings as the
drill bit pokes through.  After the hole is drilled, the putty-like
material is removed, along with the shavings that it has
caught/contained. I've heard of using chewing gum for this (but never
used it myself).  What I have used (successfully) for this purpose is
"Duct seal"- sold in electrical sections of hardware stores as a
permanently-pliable sealant for closing passage holes in sheet metal, or
masonry, that are drilled to allow for electrical cables or other
utilities.  It's not expensive, and it's quite tacky. Another option
might be "plumber's putty".

Disclaimer: I have not been following this thread to any great detail,
so if my comment is wildly inappropriate, I apologize.

Mike Dinolfo N4MWP

Well yes, but then there's nothing to lose.

I googled "welding crt filament" and came across a few stories. One guy
reported:

I recently used a neon sign transformer to weld an open heater on a B/W CRT. It took several tries to get it to hold, but eventually it did. Of course, there's no telling how long it will last.


And this, cribbed from vintage-radio.net:

Here is a transcript from the April 1969 edition of Practical Television from within an article from the late, great Les Lawry-Johns.

"The fact that a tube has an open circuited heater is usually regarded with head shaking as 'well, that's it.' This is not necessarily so. Quite often the internal break in the heater can be welded by the application of a brief pulse from the top cap of the PL500 (line output valve).

We hasten to add that this operation must be very carefully carried out for several reasons. The first is the possiblility of damage to the person doing the job, the second the possibility of damage to the line output transformer and the third the probability of destroying the tube heater completely.

The operation should be carried out as follows: Remove the tube base socket. Short pins 1 and 8 of the socket to preserve heater continuity. Connect a lead from pin 1 of the tube to chassis. Allow the set to warm up. Using a very well insulated lead, touch one end to the top cap of the line output valve and the other end to pin 8. An arc will be seen inside the tube neck. DO NOT repeat it unless it can be proved that the heater is still open circuit. Only the briefest touches is required. By this means, tube replacement may in some cases be postponed for a considerable period. In others the operation may be quite unsuccessful. This pulse application is often recommended for clearing shorts but not so often for internal welding of open-circuit electrodes."


So, it is [sometimes] possible to fix it. Looks like HV applied for short duration is the key.

Open cathodes can sometimes be fixed with something like a CR-70.

Good luck!

Paul

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows

There is always the possibility of the open being caused by bad solder joints in the tube base pins.
Bob

If you have an open heater coil, the CRT tube is probably un-fixable.

The following photos have been uploaded to the Sampling with 3S2 album of the TekScopes@groups.io group.

• 0306211734-00.jpg
• 0306211734-01.jpg
• 0306211736-00.jpg

By: Charles <charlesmorris800@...>

On Sat, Mar 6, 2021 at 01:10 PM, Marvin Moss wrote:

an open filament

Hi Marvin:
How do you know it is open?

--
Roy Thistle

OK... I set the switch while in real-time to Smooth and the display looked just like the very slow rise/fall. I suspect the Normal/Smooth switch contacts were dirty. I have exercised them a few times. So that would explain the "fix" :)

Meanwhile, I shorted the coupling cap (a .01 uf disc) and ran it to only one sampling head without the tee. It looks a lot better now. Photos added at 100 ns/div (one full cycle at 1 MHz) and at 2 ns/div.

However, I cannot get the pulses to display on 10 ns/div or faster. The timebase will trigger (trace onscreen, flat at zero) but absolutely no edges regardless of the setting of Time Position (or B Delay)! I would have thought there is something defective in the 3T77A on the faster ranges - but it works with the 600 MHz sinewave input all the way to the fastest range of 0.2 ns/div.

I also thought there might be a significant delay from trigger to display since the 3S2 has no delay line. So I connected the TD pulser directly to the Ext Trig input with the tee, then ran ~20 feet of GR cables to the sampler input. Not surprisingly, the displayed edge (with reflections) is now delayed by 30 ns or so... but it's still invisible at 10 ns/div or faster.

What's going on??

Thank you Raymond

As mentioned in the catalogs:
A1 - Universal Euro, 220VAC
A2 - UK, 240VAC
A3 - Australian, 240VAC
A4 - North American, 240VAC
A5 - Switzerland, 220VAC

Raymond

On Sun, Mar 7, 2021 at 12:41 AM, Stephen wrote:

Does anyone have any clue as to what this might b

It means it's an "International Euro, 220VAC, 50Hz" version.

Raymond

A tactic I have used when drilling sheet metal is to cover the point to be drilled with either double sided tape or folded duct tape to catch the waste material. The normal drill rotation pulls material from the hole. For the final penetration of the metal shield you could also invert the drilling - drill upwards. That would virtually guarantee no waste metal under the shield.
Don Bitters

Do you have a VGA display that you can attach to the rear video output? Do the blue stripes appear on the external VGA display?

I consider covers, or at least large plastic bags, to be essential to keep dust off of my ‘scopes. I rotate through my ‘scopes, mostly to make sure that they all keep functioning, which means that most of them sit for periods of time before they rotate back to the bench.

There is a member of this forum from whom I purchased a cover for my 2465BDV a long while back. The price was rather high (but not as high as that of a 485 cover that I had previously purchased), but I considered it to be essential.

If that member has a cover for your ‘scope, perhaps he will contact you directly (hint, hint).

DaveD

Hi,
I have a Tek 2335 that reads “OPT A1” on the front panel, next to the serial number.
So far I’ve been unable to find anything about this. It’s neither in the 2335 manual, nor the 2336 one.
These only mention an “OPTION 03”.
Does anyone have any clue as to what this might be?

Thanks

I think in the OP it was stated the 1 nSec output was "dead," but how dead?

If you're viewing on a fairly fast scope, say 500 MHz BW, you should still be able to see something of the 1 nSec signal if it's there, but you can't make any accurate assessment of the level, since it will be down the response curve rolloff, which should be not too dramatic. The 1 nSec is only one octave away from the 2 nSec, which apparently can be seen - but it already appears smaller than it really is, since you're at the scope's BW. With an analog scope, if you can see the 2 at reasonable amplitude, then you should be able to see something of the 1, if it's working. Check the amplitude spec for 1 nSec,compared to the 2. Chances are it's quite a bit smaller, but maybe enough to get by. The main thing is to see if it's there at all, and maybe it's OK, if only the scope could see it properly. Also, try to trigger the scope from one of the lower marker frequencies that's still synchronous with the 1 nSec.

Ed

Replaying to myself
I made an album with pi9ctures, same name as the post. Still not clear why I was able to directly upload pictures on Tek500 post and not here (maybe there you cannot make a picture folder; didn't check that yet)
Forgot to mention that those blue annoyances disappear when Clear Menu button is pressed (that state is presented in the last - or first - picture).
Wave-forms are from FG502, different points of triangle generator schematic - if interested about another device with abnormal behavior... there it is
TT

Replies Interleaved....

On 3/6/2021 5:21 PM, Thierry Delaitre via groups.io wrote:

When using beam finder, I can see a single vertical bar of 3cm height on the two thirds of the right hand side of the screen

Which points back at the plugin, saying that the trace is deflected all the way to the right.  Normal location for an inactive trace is the left side of the screen.

The 7B50 does not have XY mode.

It would have been nice to feed in a signal and bypass the sweep generator.

I tried to put the timebase into an input slot and I can also see horizontal bar when using beam finder

Not sure that you should be seeing a horizontal bar, but that's more or less moot for now.

The 7B50 appears to work again when the plugin was cold. The beam then disappears on the 7B50 timebase after 15/20 seconds or so after the scope is switched-on

Ok, what I suspect is that one of two things can be going on.

1) the sweep is still active, but the driver transistor that couples to the horizontal amplifier is open/leaky, or you have a capacitor that is making that transistor behave like that, thermally related.  Upsets the bias on that output stage and I think it will be turning off.

suggestions:

    if the sweep pickoff is in the plugin, then look at that.  If not, then use a separate scope to see what is hung up.  A can of freeze spray may reverse the symptoms long enough for you to figure out what part is bad.

2) the sweep itself is not working, however, the triggered light indicates (to me) that the sweep is working, since I think it's frequently driven by the sweep gate itself.

suggestion:  remove side panel from scope, remove cover from plugin, insert into far right slot, and use another scope to see what's going on.


Now, given that you do have a 7000 series scope (you'll like this part), instead of a separate scope:

put your working sweep plugin in slot #3, put the scope on chopped horizontal mode, and use the working vertical channel and sweep to debug the faulty one.

Harvey

Thanks

Thierry

Scott,

these do exist, but they are exceedingly rare. I have been searching for one for the past few months, and have only seen them sold along with the scope, and then only a couple of times.

I have a 2465 (no A, no B) with the DMM option, and I am currently using a chunk of closed-cell packing foam, with holes carved out for the knobs, in place of a front cover, so that the scope can be stood on its face in order to remove the case. I would like to try having the corners of a cover 3D printed, and then glue them together with larger panels of plastic to make a better-looking, and more durable DIY cover, but that project is far down on the list.

-- Jeff Dutky

Could you upload pictures of the malfunction ("all lighting green") and the effect of BEAM FIND ("vertical or horizontal bar")?

durechenew@... added the album TDS544A with strange display