Recent Posts

1

Test Equipment / Re: new killer scope in town - a true game changer from R&S - RTB2002 & RTB2004

« Last post by pdenisowski on Today at 10:04:01 am »

According to the Rhode and Schwarz website, I could purchase new probes directly from the company.  Support told me as an individual, not a company or part of a company, they could not help me.  Something about being in the process of changing the way they deal with non company purchasers.  Maybe US market only.

Part of the reason I purchased this scope for the higher cost was the claimed superior support.  Other companies may have the same protocol.  Nonetheless my last Rhode and Schwarz purchase.

Did support say they could not answer technical questions or that they could not help you purchase accessories as an individual?  This is an important distinction.

2

Test Equipment / Re: Cheap oscilloscope for checking mains power quality? Also logging equipment.

« Last post by tautech on Today at 10:03:38 am »

Hello,
I am a residential electrician that occasionally has to troubleshoot issues such as LED flicker, GFI nuisance trips, and well that's about it. I am looking for a very basic oscilloscope or similar device that I can connect to the lines and check for noise / power quality issues. Mostly just to verify that X is the culprit, whether X is an ev charger or dirty power from the transformer.

As such, I do not want to spend a lot, and I have a fairly limited usage, only to be able to check for a malformed voltage or current waveform at 120/240V. What's a good selection for me? How cheap can I go, and what are the minimal specs I should look for?

Also, at times I may need to respond to an intermittent issue and attach a data logger inside a panel for a day or two that can pick up on rapid spikes or sags. Again, I would use this tool rarely and don't want to spend a lot. I know there are higher end loggers like Flukes, over $1k, which is more for industrial use, but its not nearly so critical to my job. Again, what would be minimum specs and price point for that?

Thanks

Welcome to the forum.

If 2 channels are enough and you understand the risks of ground loops then SHS810X might be a solution to your requirements.
https://siglentna.com/handheld-oscilloscopes/shs800x-series/

3

Beginners / Re: 72C5 - What Is This?

« Last post by Trurl on Today at 10:01:15 am »

I think I've found the right bugger!
 72C5 (MOSFET N-ch) 2N7002T DIODES.pdf (435.29 kB - downloaded 1 times.)

It's reassuring that this is also an N-channel MOSFET (2N7002T),  and it's produced by a more recognizable manufacturer, Diodes Inc. with a datasheet that includes a detailed "Marking Information" section;

Marking Information
"72 YM"
72 = Product Type Marking Code
YM = Date Code Marking
Y = Year (ex: H = 2020)
M = Month (ex: 9 = September)

Hence, "72C5" = product 72 produced in 2015("C"), May ("5") - which seems about right for the used Gen 9 HP server PSU I'm fiddlin' with.

The following site has been the best I've encountered so far for searching SMD codes:
www.repaircompanion.com/smd_code_search

Cheers~

4

Other Equipment & Products / Re: Three most useful tools I got from AliExpress

« Last post by wraper on Today at 10:00:30 am »

It's one of the most useless tools I have. It sucks at everything besides that it actually holds the board. The only way it's useable is if you insert TH components and bend the leads so they don't fall out before putting it in holder. Inserting while in holder is a no-go. Not to say soldering under angle means that solder tends to flow downwards, especially on large solder joints. Frankly board just laying on the desk works better.

5

Microcontrollers / Re: Looking for information on TEST pin and ways to DUMP mask ROM of PIC1650 PIC16xx

« Last post by mikeselectricstuff on Today at 09:59:53 am »

Interesting read (link #1).  Link #2 might help.  I did not go through the whole thing.

https://www.eejournal.com/article/a-history-of-early-microcontrollers-part-9-the-general-instruments-pic1650/

http://bitsavers.org/components/gi/PIC/1983_PIC_Series_Microcomputer_Data_Manual.pdf

What tools to you have to read it?

EDIT: Its program ROM is only 512 12-bit words.  Do you know what the chip actually did?  If so, it might be faster and easier just to write a program to do the same on a more modern chip.

Or decap and read it optically

6

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Harrow on Today at 09:58:47 am »

Meanwhile, there are some features that the Rigol brings to the table that I find attractive, including the slimmer size, possibility of powering from a battery pack, HDMI output, easy addition of wifi capability. VESA mount might also be valuable for my limited workspace.

The last feature I noted for the Rigol leads to the first specific question for this post: Have I understood correctly that there is no way to add wireless to the Siglent other than through the ethernet port?

Second specific question: I seem to recall reading something that suggested that the probes that come with the Rigol 804 are better (? or have a higher BW rating?) than those provided with the Siglent. Is that true, and should I care?

Third specific question: I think I would likely want to "hack" either of these units up to 100MHz and greater memory depth. From what I am seeing, this seems to be easier for the Rigol than for the Siglent - true? (This also connects to the previous question - if I want to hack up to 100Mhz, are the probes going to make that less successful with one vs. the other?)

I don't want to stop you from getting the Siglent because no doubt it's a great little machine, but I'll answer your questions regarding the Rigol, simply because I can. I've been using it for a couple of hours a day for the last few weeks and continue to be happy with it.

1. Wi-Fi - Super simple to enable this and remote web control is pretty good. You can access and adjust pretty much everything you'd want.
2. Bandwidth - the hack to 100 Mhz is equally simple.
3. Sampling rate limitation - I don't think there's any need to worry about all this talk of 4-channel operation being at lower sampling rate. Whenever you want to be sure of something, it only takes a few seconds to switch off the other channels momentarily to get the 1.25 GS/s, which puts you in the realm of 200 MHz, only to find that the waveform doesn't change and then you pull off the probe hooks and starts using the spring clip and realise that has 10 times more impact.
4. HDMI - I've done this into my 65-inch flatscreen and it looks pretty impressive, but Wi-Fi web control partly negates the need for the HDMI.
5. Hacking - I'm looking forward to having a poke around just for the fun of it.
6. Size - I didn't even realise it had a slimmer profile than the Siglent, but now I know that, I am happy I have the Rigol as I'm currently using it in an extremely confined space.

7

Microcontrollers / Re: Dumped a 64mbit rom, any idea where to go from here?

« Last post by RoGeorge on Today at 09:53:39 am »

Might be MIDI soundfonts, as upgrades/addons for MIDI keyboards and/or sound cards.  If they are soundfonts, they are under copyright, so they might be expensive enough to worth selling them.

8

Beginners / Re: The old "Replace blue LEDs with red LEDs" 7 segment question (74HC595)

« Last post by trondl on Today at 09:53:33 am »

It seems like dropping the supply to 3.3Vcc takes me exactly down to the ~5mA the blue LEDs operate under (Vf = 2.1).
Uncertain if the red LEDs are as bright though under those conditions.

I now consider this to be the most likely solution, as there is a 3.3V "supply" available on the PCB for the IR receiver.
Will need to investigate if it is powerful enough though, as I guess at least having 6-700mA available is a minimum for all the LEDs and logic (56 segments * 0.005mA = 280mA + logic and headroom).
There is also another 8 regular LEDs + 595 that handle the dBFS readings that still need their 5V.

I have some doubts though, as I can see on the layout that it appears that the IR supply is just a 3V3 Zener diode dropping the 5V line.
How much current can a small SMD Zener usually handle?
>1A?

9

Projects, Designs, and Technical Stuff / Re: TekBox TEM cell – how is it constructed ?

« Last post by tomud on Today at 09:53:17 am »

Well, we're slowly starting to start building the TEM cell. Let's see what the results of the test version will be... 

10

Other Equipment & Products / Re: Three most useful tools I got from AliExpress

« Last post by pope on Today at 09:50:04 am »

Yes, it is from "my orders" page.  Looky at the ratings as well as the number.  Came fast as well.

Regards,

Dewey

Thank you.