Recent Posts

1

General Technical Chat / Re: Open source VNA calibration, conversion, touchstone read-write from python or C!

« Last post by scott_guthridge on Today at 06:16:53 pm »

Follow-up --

Release 0.1.4 adds delay parameters to all the Solver.add_*() and the Calibration.apply() methods.  These are one-way delays with positive values indicating the device is farther away from the VNA than the reference plane and negative values indicating closer to the VNA than the reference plane.  For consistency with frequency being in Hz, the delays are in seconds, so don't forget the e-12 exponent for picoseconds.

2

Beginners / Re: AA Ni-MH rechargeable battery showing VERY high voltage

« Last post by madires on Today at 06:16:33 pm »

But I don't really understand with the meter autoranging, why does 654 mV display as 0.654V but 107mv display as 107mV. As the significant digit for both is in the 100s of mV, I would have thought  it would make sense to either display both as V or both as mV.

Based on the number of digits DMMs have a upper/lower limit for each range. For example, 200 mV up to 2V. The DMM would display 0.200 up to 1.999 V. Below 200 mV the DMM switches to the next lower range, e.g. 0.0 up to 199.0 mV.

But I'm now still left with the puzzle of why the charger blew. Could it have been the battery at 107mV was just too low and caused an overload conditioon?

Shouldn't (unless the charger is cheap junk). Could be just pure coincidence.

3

Repair / Re: screws, bolts and fasteners used on vintage TE

« Last post by tatel on Today at 06:14:08 pm »

1/64" increments? Wow, fine fine tangerine.

In looking at this: https://www.amazon.com/Bondhus-16936-Balldriver%C2%AB-L-wrenches-BriteGuard/dp/B000E7ZQ8U/ref=sr_1_15

Hoping they will be good enough.

4

Test Equipment / Re: A look at the Uni-T UT210E

« Last post by cybermaus on Today at 06:11:09 pm »

Apologies if this was mentioned before in this very long post.

I have a UT210E, and it has a DM1106EN chip
But I have had it for a very long time. Maybe since 2015 or so, so it may be one of the first ones. PCB reads "UT210E Rev.1"

I hate the backlight going off too soon, and always having to move it to DC, so finding this tweak seems useful. And I had all the stuff like CH304 and clamp already in a drawer, so I thought I give it a try.
Using this video (YT watch?v=fX-Fhq9R4uY) and this specific post as a guideline.

And it all went very well. EXCEPT.... The content of my EEPROM is SOOO much different then the examples shown. None of the BEFORE values in the aforementioned post match.
So I do not dare to make the changes

Any suggestions?


Edit: anyone know how to link a YT video without it immediatly expanding and taking up all space?)

5

Test Equipment / Re: Portable Oscilloscopes List (cheap)

« Last post by awakephd on Today at 06:10:20 pm »

Setting timebase and vertical is much easier, too - dedicated buttons!

Yes, that is one of the best features / most intuitive parts of the design.

I like the display of where to put the multimeter cables:

Agreed, they did this very well. Even better would be a single set of inputs that are internally switched, but let's not get greedy ...

6

Beginners / Re: Lifting and tilting 0402 SMD LEDs by solder paste while soldering

« Last post by kanaron on Today at 06:09:20 pm »

Okay, so... As always I placed paste


I placed LEDs


I heated oven as in that datasheet which in fact apper to be from leaded paste
I heated to 160*C for 90 seconds. Then to 190-200*C for 60 seconds. Then it was quite strange to me that preheating phase states "or max. 210- 220˚C "... So just to be sure I heated from 180*C to 210*C and then I let it cool down... I did not make a photo. I completly forgot when I saw that paste still looks like paste. Is a bit harder in touch and under"paste" there is a bit harder part with a bit larger balls. But still... That was a paste. So I loaded it to oven again. I heated it to 220*C and turned heateing off. It overshooted to 230*C. Then it coolde down and looks like this:


I think that tomorrow I will make a call and send a mail to one company demanding explenations...

Anyway... It looks like I will need a few recomendations regarding solder paste. Preferably one that I would be able to get in Poland or at least in Europe...

7

Beginners / Re: Beginner Question

« Last post by RJSV on Today at 06:09:13 pm »

Here, I've placed photo of a greeting card type circuit, that waves the tail of a dog, graphic on paper.   The little pc board has the usual processor, (potted in black plastic), and in this case has 2 little solar cells, (no battery).

   So, when card is opened, the little paper 'tail' will oscillate, pendulum style, by way of a coil on the lower end, with fine wires to the circuit.

   Not exactly what you wanted, but an unusual circuit, that runs when in light, due to the solar cells.

8

Repair / Re: screws, bolts and fasteners used on vintage TE

« Last post by HalFoster on Today at 06:08:17 pm »

Google Wiha hex key sets: 35392 Metric, 35393 Imperial.  Amazon has them and they are what I use for all set screws.

9

Beginners / Re: AA Ni-MH rechargeable battery showing VERY high voltage

« Last post by MK14 on Today at 06:08:07 pm »

It can also be a chicken and egg thing.  Maybe the batteries were ok, as you put them into the charger (did you check the original voltages, just before trying to charge them)?

But the faulty/failed charger, damaged the batteries (or at least made their voltage drop too low).

10

General Technical Chat / Re: A DIY semiconductor experiment

« Last post by nebogeo on Today at 06:08:06 pm »

A little update on this project (let me know if there is a more suitable forum for this sort of thing).

I tried reducing the current by a couple of orders of magnitude, but it essentially stops semiconducting as far as I could tell - I need to pump quite a bit through this material to see any effect. I may well be making a simple mistake here, but I will also try galena, which was more commonly used for crystal radio purposes and may just be far more sensitive.

In the meantime here is a plot of pyrite, a far more common mineral ('fools gold') and a fairly typical curve showing only a mild effect:



And this one is chalcopyrite (a common ore of copper) showing a more obvious diode like properties - it can take a little while to find junctions by trying different points on the crystal surface but once you find one, it's fairly stable.



So the chalcocite is quite an outlier in terms of its performance - but they all tend to have their different characteristics (and strangely the same mineral can be different from the same type sourced a few miles apart).