Recent Posts

1

Test Equipment / Re: Amber model 3500 distortion / noise measuring set manual / service manual

« Last post by oddbits on Today at 07:26:33 am »

yes 3500 , i have 2 , one in fair condition and one in good condition , both have dead battery , one does take power the other does not, so are they worth the hassle and time to try a repair ?, Thinking i may get one good one from the 2 ? , but like i say can not find any info on the web about them.

2

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by Berni on Today at 07:21:26 am »

Resistor < Linear resistor U Nonlinear resistor
Nonlinear resistor < incandescent lamps U diodes U ...

So, you can still call it a diode, recognize that it is a nonlinear resistor and, as such, that it belongs to the more general set of resistors.

Does this make any sense to you?

It does not make sense.

All resistors exhibit electrical resistance.
All of those semiconductor devices indeed also exhibit electrical resistance.
However not all devices that exhibit electrical resistance are resistors as they are not components purposely designed to implement a well defined resistance.

Does not matter what you understand as "resistor", the vast majority of forum members you are talking to on here understand it as a device specifically designed to implement a well defined amount of resistance. You don't have the authority to redefine established industry words used by others.

What you are trying to say is that a diode exhibits the effect of "electrical resistance" or "resistivity".

This effect is not particularly special and just describes that the device can consume electrical power and turn it into something else,

The point I make is that this is ALL a diode does.
Huge resistance when reverse biased, small resistance when forward biased. This is not a side effect. It is what it does (if we neglect secondary effects due to parasitics in real devices).
It does not store energy in the electric field.
It does not store energy in the magnetic field.
It does not do whatever sorcery a memristor does.
It just oppose a resistance that takes power out of the circuit.

Yes we all agree on here that at some fixed DC operating point a diode acts like resistance.

The point is that a diode is nothing special at doing this. The laws of physics force all power consuming components to look like resistors in steady state DC. This means that at a fixed DC operating point even a memristor is actually just electrical resistance, much like a diode acts as purely electrical resistance at that DC state.

Like what else do you expect an component to do at DC? It can either act as a power source (like a voltage or current source) or it can resist the flow of current hence resistance. There is nothing else for a component to do at DC.

3

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by SiliconWizard on Today at 07:18:36 am »

That's, once again, just about modeling. You can model all your heart's content, if you find that fun or see any practical use. Ultimately, it's just MODELS.

You're taking an I-V characteristic, basically, and claim that R = U/I, except that R here is a function of U (or I). Which makes it a dubious use of the "resistor" term, as quite a few have already said.
It doesn't serve much purpose either, other than playing with I-V characteristics, which is something that is pretty basic electronics, and obviously useful in itself.

And yes, inductors and capacitors are a slightly different beast, as they involve derivatives and their model is thus a differential equation. But you can still express them in terms of a relationship between U and I; no pun intended.
If you further twist your definition of a resistor with differential terms, then inductors and capacitors also become "resistors" in your definition.

Obviously that's still playing with models, as real-world parts all have resistive, capactive and inductive components as parasitics, and while useful, even the Shockley approximation is ultimately just for the birds, as someone would say.

4

Repair / Re: Acer projector P5530 Model D1P1704

« Last post by MathWizard on Today at 07:18:18 am »

Here's some LED codes from a manual. If this thing is pretty new, you probably won't find a schematic. IDK what voltages the 240W bulb uses, but there's probably not very many voltage rails to check, if it's already running.

From the pic's I'd guess there's a boost stage like to 340V maybe, and then another stage or 2 for driving the lamp.

And the little transformer on the far left might be for 5V standby, or 5/12V for all the circuits outside the PSU. If I had this to work on, I'd make my own schematic in LTSpice, but yeah it takes time.

I'd look up all those chips on the PSU, see if they have Vcc, and if any of them have an ENABLE pin, or a power-good pin. Pretty much all those controller chips will be checking for under-voltage/over-voltge, over-current, and might be shutting down.

There could be some power problem on the other boards, you can check for shorts on some other boards. And there could be a logic signal coming back to the PSU saying to not drive the light.

If I knew the low voltage rails to the rest of the machine, I'd even try powering that from some modem or cablebox PSU, or benchPSU if you have one, just to measure the current draw.

https://global-download.acer.com/GDFiles/Document/User%20Manual/User%20Manual_Acer_1.0_A_A.pdf?acerid=636595271962374228

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Test Equipment / Re: Lecroy Wavesurfer 44MX vs WS3054

« Last post by alm on Today at 07:18:11 am »

I haven't used either scopes, but from this thread it sounds like the WS3000 series might be a bit under-powered with simpler software than the full Windows-based MAUI scopes: https://www.eevblog.com/forum/testgear/lecroy-wavesurfer-3054/

The Wavesurfer 44MX is a full Windows scope that will likely perform better, although it sounds like its power supply is not the most reliable.

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Beginners / Help Identifying an SMD component

« Last post by Jterlato on Today at 07:17:19 am »

Hi All I'm new here. Long time lurker, first time poster.

Hoping someone could help me identifying the below SMD component that I need to replace in a USB keyboard (music). Its been knocked off the board by the back of a USB B port which came apart when the keyboard was dropped with the USB cable connected.

Looks like its involved in a USB power circuit. I'm having trouble identifying it based on its markings, and i cant test it as its been destroyed. Any ideas?

7

Test Equipment / Re: SDS800X HD Bug Reports + Firmware

« Last post by electronics hobbyist on Today at 07:17:15 am »

This is not a bug. Trigger and measurement are two separate parts.

I have edited the title accordingly. I was pretty sure that it was a bug, because it really "looked" like one. 

Yes, It looks like, I also hope a manufacturer can achieve a measurement speed of 100k or even millions, but currently no manufacturer can do it unless it's capturing a frame and then measuring one frame, this will significantly decrease the capture rate, as long as the capture rate is greater than the measurement speed, this phenomenon will occur. 

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Test Equipment / Re: Siglent SDS800X HD Review & Demonstration Thread

« Last post by eTobey on Today at 07:11:52 am »

I just had a occasion, where the measurement could not keep up with a trigger rate of less than 166 times per second. Of 10 possible measurements, only 3 were measured/counted.
https://www.eevblog.com/forum/testgear/sds800x-hd-bug-reports-firmware/msg5463370/#msg5463370

Is there any information about where the limit exactly lies?

It would be an idea to add this to the table in future measurement tests.

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Power/Renewable Energy/EV's / Re: high power dc-dc isolated bidirectional

« Last post by Zero999 on Today at 07:11:17 am »

Yes. Silly thread. Ask a question about an advanced topic, then precede with beginner questions. I didn't bother responding when he asked what the turns ratio of the transformer needs to be. If you don't know how to work out something that simple, then you lack the knowledge and experience to design something as complicated as this. At least build a small scale power supply more complicated than an LM78xx circuit first.

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Test Equipment / Re: SDS800X HD Wanted Features

« Last post by electronics hobbyist on Today at 07:00:51 am »

I just turned on the scope this morning to see, that all my trigger settings were lost

What trigger type it before shutting down, and what trigger it when it turned on today? If the plug is directly unplugged, this problem may occur. If not, it may be another problem.
I haven't encountered the problem you mentioned yet, as it is currently shutting down normally(Utility - Shutdown  or  Press the power button for 2 seconds).