Recent Posts

41

RF, Microwave, Ham Radio / Re: Transistor tester

« Last post by coppercone2 on Yesterday at 11:15:07 pm »

you should try this in the repair forum since a germanium transistor is a device present in much more stuff then radios. the audio people know, and people are VERY concerned about their germanium transistors

42

Projects, Designs, and Technical Stuff / Re: 3D printing company similar to PCBWAY for circuit board

« Last post by Someone on Yesterday at 11:14:49 pm »

then you discover subtractive metal enclosures are about the same price....

43

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

« Last post by ceut on Yesterday at 11:14:03 pm »

Time has passed since my contribution here...2017   
A quick follow up of a problem of one of my 2 UT210E (the one I have given to my brother).
I have to fix his FAAC D600 motherboard (from a motor garage door) which has failed and some burned part on it.

So, after having fixed it at home, I have gone to his home, and when I have rechecked the power voltage line, his UT210E reads 51V DC    (for a 24AC 86VA transfomer, which I have checked at home at 24.85V RMS on my Keysight U1233A and with my Siglent DSO 68V peak-peak (34V max and -34V min)).

=>So big fail for this 6 years UT210e old that I have flashed and contributed for mod it here  https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/msg1316832/#msg1316832

I have worked on it for about 3 hours, reflashing other 24C02 calibration file, checking many parts etc..
All other functions worked well.
Then I have removed fully the motherboard, and found the issue 
==> Wear of the rotary switch !   
2 traces have lost their solder mask  as you will see on the photos.
I have put a piece af tape, and it is working again, with the good calibration I have made 6 years ago 
Now I have to find how I can isolate this traces... will try some UV solder mask

44

Beginners / Re: LC filtering for combined Vref/VDD of ADC

« Last post by temperance on Yesterday at 11:12:20 pm »

You can power the ADC from a proper shunt reference with a voltage between 3...3.1 V. The digital part of the ADC can tolerate at its input Vcc +0.6V (absolute maximum rating)

As long as the difference between the SPI interface maximum voltage and the shunt ref. minimum voltage stays within 0.3 V, it will work fine and the SPI interface clamping diodes will not conduct.

An LM4040 is a popular shunt reference available in 3 V, 0.1 %, 100ppm. A REF2030 is 0.05 % and 8ppm.

45

Other Equipment & Products / Re: Pace ADS200 soldering station

« Last post by Hydrawerk on Yesterday at 11:08:17 pm »

It is probably made of steel and/or aluminium. Pace MBT450 looks a lot more industrial than any today's JBC station. My workmate has a JBC DDE, that is made of plastic. Especially the tiltable LCD does not look very durable. It probably cannot show the temperature of all connected tools simultaneously. On the other hand, soldering performance might be better than PACE. There is a true two-channel AT420 hot tweezer with some 160 Watts. PACE has no such hot tweezer. Only that 120 Watt "MT-200 AccuDrive MiniTweez Thermal Tweezer Handpiece" that has the two cartridges connected in parallel or something.

46

General Technical Chat / Re: new propellantless drive company

« Last post by coppercone2 on Yesterday at 11:06:59 pm »

That is no reason to investigate an effect. Then its just boring physics instead of popsci physics.

I recall reading that it was significantly above photon drive levels though (according to their experiments), IIRC the whole point was that there is a force that is bigger then the force expected from photons.

The usual problem, that is high power electronics lol. the ones that a experienced engineer sees it as a running lawn mower engine hanging on some springs, being measured with a caliper

47

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

« Last post by IanB on Yesterday at 11:03:04 pm »

I insist that with lower frequency (everything else being equal) the voltage at the filter capacitor falls further. Model an AC voltage source, followed by a rectifier bridge, a capacitor and a constant current load. My prediction is that the voltage at the capacitor and load falls further with decreasing frequency. It must be obvious to anyone.

I understand what you are saying, but surely the design would have to be very marginal before this had an impact on the following section of the power supply?

48

Repair / Re: Please help! TANNOY PRECISION 8D dead

« Last post by Valden on Yesterday at 10:59:55 pm »

Hello to owners of Tannoy Reveal 6D and 8D monitors. I've just completed another repair, which is written up in the link below where there's a useful thread. Rather than duplicate, here it is ...

https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-audio-equipment/15433-tannoy-reveal-6d/page10?view=thread

49

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

« Last post by KungFuJosh on Yesterday at 10:55:51 pm »

I meant I get a clean sine wave up to 841MHz.

Ah, I see. Well, that's just one point in time, and the display persistence hides the deviation of the peaks from the real value. What we're interested in is observing dynamically how the waveform becomes wobbly as the signal frequency increases and gets closer to that point.

It's clearly better than the Rigol, though, which is much worse at 1/2.5x the sampling rate. I wonder how the SDS800X HD scopes perform in this scenario.

Here's, BTW, a 500 MHz sine wave captured at 1.25 GSa/s sampling rate:

I didn't get any wobble within normal range, and then I still don't get anything as crazy as what you showed in your screenshot. It mostly shrinks and the counter gets farther and farther off. Near the end before it resets, it looks a little wonkier.

Let me know if you want different parameters than what I've got here:


TSA Ultra set at 800MHz with a 10s 500MHz sweep.

50

Projects, Designs, and Technical Stuff / Re: How is a motor run capacitor sized?

« Last post by aroby on Yesterday at 10:53:03 pm »

If you're making your own board, then presumably you can change the footprint, so long as it's not too big for the case.

Have you measured the voltage across the capacitor? Does it actually get anywhere near 106V, the RMS voltage with a peak of 150V? As mentioned above, the voltage rating is probably selected for the size.

I would use two 68µF low ESR capacitors connected back-to-back, to form a 34µF non-polarised capacitor. Choose as larger case size as you possibly can, given the space constraints and voltage rating, which presumably doesn't need to be above 50V, although check first to be sure.
[/quote]

I'll investigate that. Trouble is the actuator is 1,300 miles away!  The board is quite space challenged and has a DPDT switch on the underside that pokes through the case and secures the board.   When you say 2 68uF back to back, I assume that is two polarized caps joined on the -ves and with the +ves connected to the motor?