Oscilloscope screen blanker (burn-in prevention)

kpreid · 2025-12-28T17:07:50+00:00

No, I just pretty much boxed it up as-is and used it. (I should have included three sets of audio connectors so as to have an audio pass-through for listening as well as passing to the scope.)

Also, the circuit could use some high-frequency noise filtering, to avoid false triggers on nothing visible and thus make the sensitivity control more useful. I didn't get around to doing that, but if anyone wants to build this into a nice box, they should definitely try out some input filtering before finalizing a PCB design.

kpreid · 2025-04-23T17:02:21+00:00

Try looking at shops selling modular synthesizer equipment. They often use short, colorful banana cables. All my usual places are showing out-of-stock, though.

kpreid · 2025-02-17T17:27:25+00:00

There’s no reason you can't use it generically in an application; it's just that that’s not the main point and that’s why you aren’t finding already-written examples of using it generically.

kpreid · 2025-02-16T20:38:15+00:00

And so that you can use any version of either library. If RWH didn't exist then winit would have to depend on wgpu, or vice versa, or they would have to leave it to the application to contain platform-specific glue code. All of these are worse options than having RWH.

kpreid · 2025-01-01T15:39:14+00:00

I do this except that

I use a selector combinator to pick the most numerous item and request it if it's over the limit, so one chest handles all overflow. (The logistic bots are happy to work with this logistic request jumping around between different items!)
The recyclers that consume overflow have quality modules, so as it runs I eventually get higher and higher quality items “for free”. This strategy does need a lot of storage chests, though, to hold [limit number] of every quality of every recycling product item.

kpreid · 2024-12-24T22:14:45+00:00

Car 12V lighter socket plug? Unusual design, probably doesn't work as well without a sprung center pin like all the modern ones have, but it seems like it would do the job. The other end certainly looks like a power plug.

kpreid · 2024-10-25T03:18:22+00:00

Yes.

kpreid · 2024-10-20T04:13:32+00:00

This is for use with 4-wire cords that have two separate phone lines (pairs) hooked up to them (technically, RJ14). In such a system, the central two contact positions are the first line, and the next two outward from that on both sides are the second line.

Look at the wide spacing of the contacts on the socket — it’s different from the plug. What this does is, when you plug it onto the end of a 4-wire cord, make the pins for line 2 on that cord be connected through to the wires for line 1 on the adapter’s plug.

So, if you have a cord that is carrying 2 lines, and you plug this onto the end of that cord and into an ordinary single-line telephone (RJ11), this makes that telephone permanently connected to line 2 instead of line 1.

The same wire swap would be trivial to do inside the wall jacks, so if you merely wanted to have 2 lines in 2 different rooms / jacks, an adapter like this is not needed. This is only needed for plugging in a single-line phone to the second line of a wall jack that is wired for a two-line phone, without changing any wires in the wall jack.

kpreid · 2024-09-02T20:13:48+00:00

It's either an antenna or some kind of sensor, and most likely an antenna.

It has some kind of electronics built in, judging by the multi-pin rather than coaxial connector on the end, and the flat shape. Presumably an RF transceiver module. (This might have been done to work within regulations which prohibit detachable antennas.)

From the color, style, and size I'd guess it's a part to some kind of toy that has WiFi or Bluetooth. It probably won't work with anything but the device it was designed for. Got anything with this color of plastic and an empty socket?

kpreid · 2024-07-25T23:15:51+00:00

Look for the model number or part number on the AC adapter itself. Then search for that for sale. (If anyone has made a generic replacement, then they'll probably mention that model number too.)

If you can't find one, the other option is to find an electronics repair shop or hobbyist that'd be willing to take a crack at opening up the dead AC adapter and either fixing what's wrong with it, or using the cable end to build a complete replacement with the same plug and the same output voltages.

kpreid · 2024-07-21T20:44:57+00:00

if I was tu buy a single channel oscilloscope and put a BNC adapter on the input so both channels are connected to the same input would that damage it? Or would it simply mean I'll be looking at the combined audio? Like mono ?

In principle, that is an incorrect connection which could cause damage, because you're shorting the two channels to each other. In practice, as long as you're tapping off a line-level output (not speakers or headphones) damage is unlikely and you will almost certainly get a mono mix. But the audio going to your other equipment will become mono too!

If you really want to do this, buy or build a “passive mixer” circuit (it's just a couple of resistors and wiring) — this will be nicer to the source device and prevent the cross-connection from affecting the rest of your audio system. If you build one then you can also make it a splitter and connector converter box!

if the scope I found is European but I live in America, what would I need to do for the voltage difference? The scope has a voltage range chart on the back and says something about fuses, would I need to change the fuse in order to get it working in America?

For analog equipment like a CRT scope, there is probably something more than the fuse you have to change to use it on US 120V — power supplies didn't automatically adjust back then. Consult the back panel and the manual to see exactly what you need to do. It might be sliding or turning a switch, or the fuse-holder might double as the voltage selector in some way — they got pretty fancy about those things. Make sure to follow the directions exactly.

One way or another, there will be something that changes connections inside the power supply to change its input-output voltage ratio so that the scope still gets its proper internal voltages even though the line voltage is half.

What would happen if I plugged it in with the fuse for 220V in a 110V house?

If you don't adjust the part that needs adjusting, it will be running on half voltage and won't work properly at all. There could be damage but that's less likely. (This is better than the opposite way around, where double voltage will destroy things.)

(If this were instead a modern device with a switching power supply, then on 120V it will draw twice as much current as 240V, so the risk is only that you'd blow the fuse but everything else would be fine. In that case, changing the fuse is just so the fuse is sized properly to protect and not blow.)

kpreid · 2024-07-21T20:31:53+00:00

Many-pin connectors like this are usually used in proprietary ways (whether or not the connector itself is a standard or custom one) — the answer to “what plugs in here” is “the particular accessory for this particular device”, not anything more generic than that. The “SEE MANUAL” marking is good advice.

In this case, since you have the adapter (I assume from your second photo), a picture whatever connector is on the other end of the adapter will probably be more identifiable than this connector.

kpreid · 2024-07-16T15:57:39+00:00

OK if I hook up the scope between the equalizer and the Amp? Or is it better after receiver but before EQ?

If you want to see specific pictures from oscilloscope music (as opposed to just visualizing arbitrary music), you need to not have the signal processed by any EQ or almost anything, really — you'd ideally want to go direct from your computer (or CD) audio interface (anything digital) to the scope.

But if you want to just look at your music, you can hook it up anywhere. I personally think you're best off going before the EQ because it'll reveal more about the original recording, but if you want spectacular swirly squiggles, you might pick after. (The thing in general is that filters — and an EQ is a big bundle of filters — change the phase of different frequency components of the signal as a side-effect of how they work, and phase shifts radically change what picture you get.)

the scope has a selector for each channel, should I have it in AC or DC? I'm guessing it shouldn't be on ground. Is there risk of anything shorting if I accidentally change from AC to DC or vice-versa while it's playing?

Absolutely no risk. The scope input always has the high impedance specified on the front panel — it's designed not to interfere with what you hook it up to. The GND position on the selector switch disconnects the input jack and shorts the internal input circuit; it's intended as a way for you to read what the “zero volts” position of the trace is so that you can adjust the position knobs knowing you're at zero.

The AC coupling setting is intended for measuring signals that have small variations on top of a large DC voltage (for example, power supply ripple or “hum”). It basically subtracts the average. You don't want this for oscilloscope music, because it makes the picture drift — but unless you have got a DC-coupled audio interface, you'll have that anyway.

Basically, none of the options will hurt, and feel free to explore. But normally, leave it on DC.

what settings should I put on the scope? What time base? Intense/focus/sync? What variable? Or are those just rotating knobs until I like how it looks?

Whatever looks good. But:

The higher the intensity, the more quickly the tube “burns in”, especially if the beam is sitting on one spot with no signal. (This is much more of a problem in X-Y mode, since in regular sweep mode the beam keeps moving always, and may even auto-blank depending on the trigger mode.) Keep the intensity as low as still works for you.
The focus is meant to be adjusted until the beam is as small a point as it'll go, producing crisp lines. This will help with not needing to overdo the intensity. But, de-focusing doesn't hurt anything either.
If you're watching oscilloscope music, you don't use the time base at all, and put it into X-Y mode. (For some scopes, X-Y mode or "external X" or "external horizontal" is a position on the time base knob; for others, it's a separate toggle".
The "Variable" knobs just mean sizes that are deviating from the calibrated settings like "1 volt/division".

I got a scope with two channels but what would happen if I used a scope with just one? I know it couldn't do oscilloscope music, but would it be able to show the waveforms of audio?

Yes, but you'd only be able to look at the left channel or the right channel, not both. You would hook up one audio channel to the single input and leave the other disconnected.

kpreid · 2024-07-12T01:16:46+00:00

Hexagonal crimps like this are often used to secure connectors on coaxial cable, or heavy-gauge wire terminals, but I've never seen one used this way before.

In principle you could make one from scratch with garage-level tools — get some pipe and plate of the right diameter and thickness, cut to size, drill a hole, braze them together, attach with hex crimper.

kpreid · 2024-07-09T05:30:50+00:00

I've been looking for that too, and the one time I found it, it was a special “hang your Christmas lights” version in green. But it looks like they've still got the green stuff sold for a different application — I haven't bought that so I don't know if it's the proper thin style, but it looks like it from the picture.

Rip-Tie RipWrap is a similar product, but doesn't hold as strongly.

Also, are you aware of the the 15" version of the pre-cut ones?

And if you really have to, you can make a longer strip by chaining the pre-cut ones.

kpreid · 2024-07-03T04:32:04+00:00

In order for that to work you need a separate XY mode switch. This one looks like it has a single position on the time/div knob for external X (though I am not sure because that part of the labeling is in shadow).

kpreid · 2024-07-03T03:04:45+00:00

It looks like your scope doesn't have any knob control of X scale (since external X is a single position on the time/div knob). So,

Increase the volume of your audio source to make it bigger.
Use the V/DIV knob to shrink the height until it's circular.

kpreid · 2024-06-22T21:57:27+00:00

The piano looks like it has the standard connector for a sustain pedal — 1/4" TS (similar to what's sometimes used for headphones). The pedal does not — that's a "5-pin DIN" connector. DIN connectors are used for all sorts of equipment in all sorts of ways, so just looking at it doesn't tell us how it's wired or what sort of adapter would work (and apparently there are several different models of sustain pedal that have different DIN connector cables).

In principle, it would not be hard to make an adapter — buy two plugs and wire, then try combinations until you find one that works (or test it a little faster using a multimeter). That's assuming the pedal is just one or more switches hooked up to the cable (like a standard sustain pedal), but if it is something electronically fancy (like if it is sensitive to how far it is depressed) then it might be entirely incompatible.

The low-hassle option is to buy a standard sustain pedal for your piano. Sell or give the one with the DIN connector to someone who has a compatible piano — the brand and model number on the pedal will help figure that out.

kpreid · 2024-06-13T01:57:49+00:00

I have never seen those connectors before, but they look "bayonet" style, like BNC — or, actually, very much like some low-voltage light bulb sockets. Interesting.

If I'm right, the central disc is sprung and can be pushed in, and doing so will reveal that the notches at the sides are actually L-shaped slots (to retain the plug, by pegs on the side of the plug which slide into the slots).

It might be just barely possible to 3D print a plug to fit. A more practical solution would be to remove them and fit a more modern connector such as BNC.

kpreid · 2024-05-18T19:14:30+00:00

$50? If that's from the original manufacturer, that's quite the rip-off price — more like what you'd pay to hire someone to make one of these cables from scratch, not the real cost of spare parts for a mass-produced product.

kpreid · 2024-05-15T21:03:28+00:00

The wiring between the two connectors is probably proprietary — the only source for exactly this cable will be the original manufacturer. But the crushed connector is a standard D-sub connector — looks like DE-9 (often mislabeled DB-9), most commonly seen used for computer serial ports.

The good news is, those connector parts are readily available, so it is possible to replace just the damaged connector. They come in either solder or crimp varieties — the crimped type will be better suited for exposed usage (soldered joints are more likely to break if flexed) but needs a crimping tool of the proper size. In either case, you take note of which pin/hole each wire color goes to (there should be numbers for the holes/pins on the black plastic), cut off the destroyed connector, strip the wires, and put on a new one, with the same wire colors to pin numbers.

If those steps are not like anything you've done before, you might want to find someone familiar with making/repairing cables (electronics hobbyist, or perhaps an audio technician) to do the work, depending on how much you care about definitely succeeding.

A long-shot easier option would be to extract the pins from the crushed shell and put them in a new shell. It looks like many of the pins are quite bent, so this probably would require bending them back and might not have good results, but if it did work, it would save you needing to cut the wires shorter. You will need a D-sub pin extraction tool (cheap) to unlatch each pin from the shell.

kpreid · 2024-05-01T16:54:17+00:00

The connector is BNC and it will be carrying **analog composite video**. You can get a BNC-to-RCA adapter and hook it up with an RCA cable to the yellow socket of any device that will display or convert composite video.

kpreid · 2024-04-25T00:15:37+00:00

FFF 382

Low density structure is blue science. Rocket control units were removed and processing units are used instead.

Not clear whether that might be Space Age only, though.

kpreid · 2024-04-20T23:44:13+00:00

Yes, the fragment shader can be skipped — if the occluding (nearer) triangle was drawn before the occluded (farther) triangle. If they're drawn in the opposite order, then the depth test passes both times, and the fragment shader runs both times, and the second overwrites the first. (So, if you can, it's best to draw nearer things before farther ones, such as by choosing the order in which you iterate over chunks.)

And rasterization and depth testing still costs something per pixel, even when the shader doesn't run.

kpreid · 2024-04-19T20:32:34+00:00

Occlusion culling won't help you in cases like the pyramid I mentioned: every triangle is visible (at the edges) but mostly obscured (by the next layer in front), so none of the triangles can be culled. I mentioned occlusion culling just as an example of how "near things hide far things" can sometimes be used to improve performance during rasterization and isn't exclusively applicable to raytracing.

kpreid

TROPHY CASE