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It would really help if people put an approximate location on ads.

Though it seems no location means the seller must be American as they are the ones that don't bother saying where they live (and not adding to the stereotype that Americans see themselves as the only place in the world...)

Try posting on the Logic Analyzers forum on groups.io.

If you're looking for direction, you'll need two of them

I'd be tempted to use a resistor and neon with a one KV diode in series with the neon.? The neon will limit the maximum voltage to about 100 volts or so.

so:? resistor connected to a neon with a series diode, connecting both across each other, and the diodes reversed.

Might be a good idea.

Harvey

Could you use a small (NE-2) neon bulb for this? I recall holding the lead
of one and shuffling across a carpet. I got the bulb to flash.

Steve H.

On Wed, May 8, 2024 at 21:03 Ed Breya via groups.io <edbreya=
[email protected]> wrote:

The LEDs would protect each other from reverse breakdown. They should be
stout enough to take the forward hit and flash. If not, you can put some C
across them or R in series to soften things up (which would also stretch
the pulse for better visibility). Try it and see.

What's really needed to assess part durability is a power rating and an
energy rating. You won't find energy rating for LEDs, so have to
experiment. If you study the HBM you'll have an idea of the energy
available from your own spark. Unfortunately, I don't think there's a spec
for SCM, but you can be sure it would be quite a bit more C, and nearly
zero R. Good luck.

Ed

Very nice. How do you get such a smooth cut of the can?

George KD6NEW

Yes indeed, Steve gets the prize. That's what it would be called if such a thing existed.

Ed

Shopping Cart Model??

Steve Hendrix

Sorry, what's SCM?

On Thu, May 9, 2024 at 3:03?AM Ed Breya via groups.io
<edbreya@...> wrote:

The LEDs would protect each other from reverse breakdown. They should be stout enough to take the forward hit and flash. If not, you can put some C across them or R in series to soften things up (which would also stretch the pulse for better visibility). Try it and see.

What's really needed to assess part durability is a power rating and an energy rating. You won't find energy rating for LEDs, so have to experiment. If you study the HBM you'll have an idea of the energy available from your own spark. Unfortunately, I don't think there's a spec for SCM, but you can be sure it would be quite a bit more C, and nearly zero R. Good luck.

Ed

The LEDs would protect each other from reverse breakdown. They should be stout enough to take the forward hit and flash. If not, you can put some C across them or R in series to soften things up (which would also stretch the pulse for better visibility). Try it and see.

What's really needed to assess part durability is a power rating and an energy rating. You won't find energy rating for LEDs, so have to experiment. If you study the HBM you'll have an idea of the energy available from your own spark. Unfortunately, I don't think there's a spec for SCM, but you can be sure it would be quite a bit more C, and nearly zero R. Good luck.

Ed

Still looking.

Anyone have any experience of the TLA622 logic analyser, trying to sort display issues on one I have aquired

On Wed, May 8, 2024 at 6:29?AM Ed Breya via groups.io
<edbreya@...> wrote:

When one object dumps charge to another with enough energy to make a spark, then you don't need any sophisticated instruments to tell the polarity. A couple of anti-parallel-connected LEDs will suffice. Electrostatics was pretty well figured out by brilliant minds long ago, with comparatively crude instruments, way before tubes and transistors and ICs. Except for scientific curiosity, there's no need to recreate it (aka reinvent the wheel) to answer the question.

Any DMM in its voltage mode can sense the currents flowing in an electrostatic situation, so just bring a handheld DMM in its lowest VDC range, clamped with those anti-paralleled LEDs or regular diodes, and have at it. Use a simple, cheap DMM, like a Harbor Freight one, in case you accidentally discharge into a bad spot. Or, just leave out the DMM and use the LEDs. Don't forget the clipboard, paper, and pen to record the results, and try to look cool while doing it. Don't use a phone - keep it well away from all this activity.

One thing that may help is to look at the various HBM (human body model) electrostatic specifications, to get an idea of magnitudes involved. You can only store so much energy in practical conditions.

Ed

the led idea is pretty good. i was considering something like that for
a moment, but then i thought maybe the voltages involved would just
burn through a silicone junction.

my phone's been in my pocket during each esd event in that store, and
it still works. those things are really well made nowadays.

Hi everyone, I'm searching for some Tektronix 500 series plugins and wondered if anyone on here may have one for sale. They don't need to be working, but do need to be in good cosmetic condition and complete. I'm trying to find :

1l5, 1l10, 1l30, 1l40, 1l60
S type
Q type
1S2

If you have anything, please let me know!

Julian

This is probably familiar to most people who have ever tried to replace an old electrolytic capacitor.
It is very easy to make an adapter, at no cost.
It is enough to cut off the edge of the old electrolyte, approximately 3 millimeters from the edge.
You will get an outer ring that fits perfectly back to where it was, and the bakelite center will serve perfectly to place a modern electrolyte on it.

Here are pictures of how I usually do it:

/g/TekScopes/album?id=294954

@Beros <radiobero.bb@...> added the photo album can electrolytic adapter ( /g/TekScopes/album?id=294954 )

On Tue, May 7, 2024 at 05:12 PM, Dale H. Cook wrote:

On 5/7/2024 4:43 PM, cheater cheater wrote:

also why buy aluminium leaf? why not use alu foil?

Aluminum foil is far too thick. An electroscope needs minimum mass, and that
means leaf, not foil. The repulsive force in an electroscope is far too low
for foil to work.

I believe it's the stiffness, more than the mass, that's important, but the problem remains that the electroscope needs to be sensitive to extremely small forces.

For detecting direction of current flow you want a sensitive galvanometer, of
the type used as a detector for instruments such as a Leeds & Northrop Type
K-3 Universal Potentiometer. You would probably need an adjustable current
limiter of fairly high resistance to avoid damaging the galvo.

A galvanometer will tell you the direction of current flow, but it won't tell you which side got the built-up charge. He might be able to discern this by taking an electroscope around the store and touching it to various things, the cart: his finger, something "grounded." It should be possible to eventually pick out which item is different. Even this may be difficult, because I'm not sure what effect charge on the electroscope housing may have. It might be necessary to ground the housing with a wire that's long enough reach "ground" and also allow the electroscope to move around to reach everything he wants to check. (The problem here is that electroscopes traditionally have two glass windows, so the interior is not a completely field free region.)

--
Jim Adney
Madison, WI USA

Mark,

I checked those and one of them is well within tolerance. The other one is just at the high end of its tolerance. I may replace one or both of them but they should be okay for now.

Thanks!
Barry - N4BUQ

Barry,

These are a bleeder for the cathode circuit and partial divider for high voltage and focus circuit. I replaced mine with 1W 1% types and spaced them off the board. The 1W types I use are about 1cm in length, not 3,68 x 8,74mm types.

You will find the two 22meg resistors to be well out of tolerance. Use VR37 Vishay types.

Mark

Without looking, that sounds like the typical "focus string" divider that probably includes the focus pot somewhere, to get the right operating voltage for the function, and it possibly does other things too. Carbon composition resistors are often used for this, and they tend to drift upwards over time. Your idea to mount the replacements with more board clearance is sound.

It's also possible that strings of resistors are used for feedback in high voltage regulator circuits, but if so, they would be better grade metal film resistors. Tek hardly ever did this for CRT HV regulation - they used instead a carbon or metal film resistor network on a ceramic substrate. You can usually spot this part easily in the circuit.

Ed

Hi All,
I've a TM504 with 4 modules for sale.
Also a Scopemobile Type 204. The TM504 tucks nicely into the 204.
Both can be seen here:


Local sale & PU only.

Please respond privately off group. I will not respond here, to preserve the bandwidth/protocol of the group.

Thank you - Bob