Recent Posts

1

General Technical Chat / Re: The strange case of phase angles

« Last post by tooki on Today at 02:39:20 pm »

And what that means is that to solve it trigonometrically, you can’t use the impedance (vector addition of resistance and reactance), but rather the admittance (vector addition of conductance and susceptance).

As an aside: as someone who sucks at trigonometry, I just use my calculator’s ability to work with polar complex numbers. So calculating I_T, for example, I just type: 0.02 + 0.008∠-90 + 0.01571∠90 and get 0.02143∠21.1.

2

Projects, Designs, and Technical Stuff / Re: Heated Ferrite == Useless Ferrite

« Last post by GelatinCapacitor on Today at 02:39:04 pm »

I definitely put effort into making sure the cores were put together the way they used to, and in the best way I could, and to hold them tightly with kapton tape.

For most of my attempts, I separated and put the core together many times just in case I did something wrong.

All of the cores kept glue were it used to be, including the center gap. I did not try to take away any glue. All of the attempts were made once everything completely cooled down. At least visually, all of the cores seemed to fit back together perfectly, with no additional gaps or anything. Perfect lego pieces.

Many of the cores were not even perfectly aligned to begin with. I replicated that misalignment just in case. I also tried better alignments for the same cores.

A couple of the cores had little square or circular shaped spacers in the middle. Of course I did not remove those. All of these cores were difficult NOT to align correctly.

For a few of the cores, I did not even take the cores apart, just made sure I got the 'ready to take apart' signal. Same results.

For all transformers, after declaring them dead, I removed all windings and, not very properly tested for loss of enamel. I did not detect any evidence of loss of enamel, but maybe the way I tested this is completely off. In the iron tests, I did not measure temperatures above 120°C on the cores and 60°C on windings, so I do not suspect the windings in the iron tests.

If I were to redo the tests, I would now also try to measure the resistance of the windings to check for loop shorts. By running current across them before and after heating.

Maybe even take the windings away before heating, and then put them back afterwards. That would drive me nuts.

3

Repair / Re: FLUKE 8920A RMS AC meter failure needs help

« Last post by daisizhou on Today at 02:35:56 pm »

I tested TP3, TP4, TP5 waveform video, please check

https://youtu.be/qDG2JKikg8s

4

FPGA / Re: Help on translate schematics to Verilog.

« Last post by Wiljan on Today at 02:35:25 pm »

[

If you use Quartus and have made a schematic, then while the schematic are selected you can click "File"/"Create/Update"/"Create HDL Design File from current file" (the schematic)  select verilog, give it a name, quartus will then make a verilog version of your schematic.

Thanks, I did it.I have these other two KiCad symbols that I'm try to identify, are they a D flip flop and a D latch with enable?Not sure though.

See the difference on the 2 flip-flops the one with clk will only change data on posedge of the clk the other will do as long enable are valid

5

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

« Last post by pdenisowski on Today at 02:14:07 pm »

lets wait HAM fellows (names with numbers and who build their own radio) to chime in what they have to say

Depends on the kind of radio you're building (or operating)   In the United States, there are amateur allocations at 902 MHz and 1240 MHz, and some experimenters go even higher.

https://www.arrl.org/files/file/Regulatory/Band%20Chart/Band%20Chart%20-%2011X17%20Color.pdf

One of my commercially-produced radios (the Icom 9700) has 144, 440, and 1200 MHz,  Icom is also investigating making amateur transceivers for the 2.4 and 5.6 GHz ISM bands

https://www.icomjapan.com/api/download.php?page_id=66&fl=JTJGdXBsb2FkcyUyRmxwJTJGc2hmJTJGU0hGX3Byb2plY3Rfdm9sMV9lbmcucGRm

73, Paul, KO4LZ

6

Test Equipment / Re: Tek 2465 Horizontal Sweep Issue

« Last post by MarkL on Today at 02:13:25 pm »

On your probing of pin 18, the ramp will take as long as the sweep, approx. 10x the sweep setting to cover all 10 divisions.  If you're measuring with a voltmeter with the prescribed test settings, you'll never see the ramp because it's too fast.   One thing you could do is turn the sweep down to 0.5s/div.  The sweep across the screen will take about 5 seconds, and you should be able to see such a slowly changing ramp on a voltmeter.

Since you're getting a vertical deflection, you could also probe pin 18 with Ch 1, again at a slow sweep.  With this problem on your scope, what you should see is a dot slowly going up and then resetting, repeatedly.

What are you seeing on the back panel A GATE OUT?  A logic high here indicates that the A sweep has been triggered.

Does XY mode work?  Seems that it probably should given the other symptoms.

I would also try removing and gently cleaning the contacts with isopropyl on hybrids U500 (trigger) and U650 (display sequencer).  Don't mess with the nut on U800; it is prone to failure from mechanical stress.

7

Repair / Re: Desoldering advice

« Last post by fmashockie on Today at 02:12:59 pm »

After seeing the photos, the reason you are having so much trouble desoldering this relay is because look how beefy the traces are that it connects to.  You need a lot of heat to get those relay leads removed.  When I am working on boards like this (with thick power traces) I use a combination of hot air station and my iron.  I hold the iron on the lead to be desoldered, and hover the hot air over it.  This probably isn't good for the tip (I haven't seen any issues with my tips and I've done this fairly often), but this works.  Of course using a larger iron could possibly work.  But this method works fine with a Hakko FX-888 station and a decent hot-air station.  When I am dealing with multi-lead components like a relay that you can't just pull out one leg at a time, I also use solder wick to suck up the solder at each leg.  Again, you are only going to be able to do this with enough heat.  Use flux as well and continue to wet the wick with flux to get the solder to adhere to it and away from the leg to be desoldered.

The same goes for getting that relay back on the board.  You're going to need a lot of heat to get it soldered back on.  Same method works.  Add solder with the iron, then heat it up with both iron and hot air to get it to form a nice joint.  Obviously do this for as short a time you can to not overheat the component.

8

Metrology / Re: ESI RV622A Resistor Repair

« Last post by gmilliorn on Today at 02:12:16 pm »

It seems Manganin can be soldered, based on web searches plus comments from Edwin G. Pettis and
others such as here:
https://www.eevblog.com/forum/metrology/manganin-zeranin-enamelled-wire-availability/

From the close up of another resistor, the Manganin appears to be soldered while the lead is welded.
Even though they look quite different, I assume the end-caps must be Manganin as well, or else the
TCR would be affected?

There are cheap spot welders on ebay, used to weld batteries.  It might be interesting to try one, it's
an inexpensive experiment and would prevent desoldering the manganin wire connection, perhaps.

9

Security / Re: Microsoft repackages apps with a telemetry .NET wrapper

« Last post by madires on Today at 02:06:56 pm »

From an EU point of view (GDPR) the rules for telemetry are quite clear. Telemetry can't be forced upon the user, i.e. the application has to run also when users deny the collection of telemetry data. Users have to be informed about all the details (what, why, how long stored, and so on).

10

Beginners / Re: Convert US standard 115V to International 230V

« Last post by radiolistener on Today at 02:04:09 pm »

Because you don’t, and that entire reply is proof of this. You just bark back, but never accept responsibility for mistakes, nor accept that others are correct. Look at the part of my sentence above that is in italics. (And which was in italics in the original.)

Your personal subjective opinion about persons is off-topic.

Your first reply in this thread, long after OP had listed the part numbers of the power supplies used, you suggested 1. using a motor-generator set, and 2. to consider switching to an SMPS inside.

Both of those suggestions are completely irrelevant and useless at that point in the discussion because it had already been established that it uses two universal-input SMPSs.

This shows you did NOT read the discussion before replying.

When I posted my first reply in this topic I didn't seen complete list of power supplies which are used on OP device. And correct me if I'm wrong, there is still no such list. Also I noted in the first OP post that his device power consumption is about 2300 Watt. And two PSU which he later provided for example is about 750-900 Watt in total, which is just about 40% of total device power consumption. So there is no way to decide if all of his PSU are compatible with all mains standards. I already explained it, but for some reason you're didn't read it.

I don't see why my post is completely irrelevant, the second part covers SMPS with universal input.

But even if all of their PSU are compatible with all mains standards, that is not enough to claim that medical device which uses these PSU will be compatible with all mains standards.


Regarding to the mains filter mentioned by IanB, it doesn't related with 50/60 Hz at all, their goal is to remove common mode currents in order to reduce EMI. I was talked about different filter which is used on device sensors ADC and in DSP stack to reject 50 or 60 Hz carrier from measured signal which appears due to interference from mains wires and due to leakage through PSU. It is software configured depends on used user environment. In medical device some signals working range may be very close to 50/60 Hz and even may cover that frequency and needs to be carefully processed with take into account the frequency of used mains line. Because interference level from mains frequency is pretty strong and it's presence can affect measurement results. This is why using PSU with universal input is not enough to decide that device is compatible with all mains standards.