Recent Posts

1

General Technical Chat / Re: Power supply design/manufacture is a waste of time?

« Last post by Nominal Animal on Today at 08:09:05 pm »

It's the same problem all over Western education, from kindergarten to universities.

Practical understanding, and the ability to apply your knowledge to solve practical problems, is seen as neglible importance compared to appearances and social awareness and everything else.

The only reason I, basically a functional potato, was successful in the IT/software development/product development business, was because I didn't go by what the clients told me.  I somehow managed to investigate their actual practical needs, and address those instead.  Talking to artists, I learned how to use technical know-how and understanding the limits to guide them toward an achievable result without violating their vision/idea, and they really liked working with me.  (Except for one, who liked to exhort students to "be real humans, and not just students".)

If I can do it, it cannot be that hard.

What is hard, is convincing the administrators, leaders, and political figures that this is what works, and that their flimsy-flamsy talky-talky appearances-centered reality-ignoring crap doesn't.  So many of them are the 'Hyacinth "Bouquet" Bucket' of their positions it is uncanny.  Hints are welcome, if you've managed to do that.

2

Repair / Re: Need advice on repairing some blown MOSFETs on a Headphone circuit board

« Last post by Fulmir on Today at 08:08:11 pm »

I still need to check components, and will do so, but this may be relevant...

Some additional info on a likely failure mode is that these headphones have two connection options, one to a "base station" and another via Bluetooth, and the two can be active at the same time, as well as being able to adjust volume between the two. The specific failure is that the headphones won't connect to the base station at all, won't stay powered on unless plugged in or connected via bluetooth, and won't actually let me turn on bluetooth unless I set them into searching for connection for the base station while plugged in and then turn on bluetooth. None of this is expected, everything should turn on from any mode.

My original supposition was that the problem may have to do with some kind of current or voltage spike when turning on one or both modes, though as noted I'll definitely be checking for dead components.

If I don't find any I'd appreciate recommendations on possible upgrade paths for the MOSFETs. I'm familiar with them failing, but generally in higher power applications where I know things like the activation voltage. Here I'm rather wary of mucking things up since I don't know the expected properties, and don't have a great way of measuring.

Oh, also, is there any way to ID that Inductor? It is missing a small chunk, probably from 'shrapnel' from that one MOSFET going, and I'd rather not find out it's the cause of all my woes here when something else goes "pop"... 

3

Security / Re: Encrypted file and unencrypted copy together, can password be calculated?

« Last post by Bud on Today at 08:04:36 pm »

There are law enforcement agencies and national security agencies already storing as much encrypted content from criminals and opposing countries as possible in the hope they can soon decipher them with these new computers.

I'd like to see this proved but i am sure you wont be able to prove it, as this is just a conspiracy speculation. The economics of that is very much questionable.

4

Buy/Sell/Wanted / Re: FOC (UK) Free: Electrox Cobra 150w YAG laser (non fuctioning)

« Last post by billtodd on Today at 08:01:13 pm »

YAG lasers are extremely dangerous to your eyesight!

Yes indeed. At 150w this is extremely dangerous to all parts of a body ! You'll have to convince me you are competent before I  let you have this

5

Beginners / Re: linear regulator (igbt) schematic

« Last post by ArdWar on Today at 07:57:07 pm »

would the schematic work?

No?

I mean, that's generally not how MOSFET work (and IGBT is just MOSFET slapped into BJT). You bias your gate at 5V, and the IGBT will drop its emitter to who knows what voltage depends on V_GE(TH). You can do that with BJTs because V_BE drops are generally pretty small, it isn't the case with MOSFETs where V_GS(TH) are often large and not well controlled.

6

Test Equipment / Re: New handheld 2ch DSO, Mustool MDS120MC2, claimed 120MHz/500MSps (June 2024)

« Last post by tautech on Today at 07:56:15 pm »

Most of this info is from learnelectronics video below:
- 120MHz single channel
- 40MHz dual channel
- equivalent max sampling rate 500MSps
- looks like it uses MCX connectors
- storage depth 12.8div (?)
- vertical sensitivity 50mV-100V
- time base 6nS-50S
- trigger auto/normal/single, rising/falling edge
- signal generator: sine/triangle 100kHz, square 3MHz, 0-3V
- 320×240 2.4" display
- 124×80×35mm, 187g

At Banggood for around US$80:
https://www.banggood.com/MUSTOOL-2IN1-120MHZ-Dual-Channel-40MHZ+2-500MS-or-s-Handheld-Digital-Oscilloscope-+-Function-Signal-Generator-MDS120MC2-p-2011184.html?cur_warehouse=CN

A short review by learnelectronics, he wasn't very impressed and
thought it was a bit too expensive: https://youtu.be/JNNQ12k7EK8

Good luck even resolving 10mV of ripple on a power rail with such poor max sensitivity. 

7

Buy/Sell/Wanted / Re: WTB (UK) HPAK 3458a Faulty / Damaged

« Last post by Stray Electron on Today at 07:52:57 pm »

cheapest so far

from USA
https://www.ebay.com/itm/156171948041?
2589 $ usd ??

   You left out this part "his item is used, and power tested ONLY. It DOES power on. Sold AS-IS for Parts/ Repair. No"

from japan  with problems
£2,830.74
https://www.ebay.com/itm/156171948041?

8

Test Equipment / Re: New PicoScope 3000E Series 500 MHz 5 GS/s digital USB oscilloscope

« Last post by electr_peter on Today at 07:50:57 pm »

I'm still surprised there aren't more good USB scopes - seems like they'd be cheaper by eliminating the need for control panels and display...  They're all software inside now anyway = just package up the front end and acquisition components and you're done.

There is Micsig VTO/VATO2004 for ~300-400€. it seems to be the same Micsig handheld battery operated scope, just without buttons/screen and controlled via Android app.

9

Buy/Sell/Wanted / Re: FOC (UK) Free: Electrox Cobra 150w YAG laser (non fuctioning)

« Last post by Stray Electron on Today at 07:49:17 pm »

    A strong word of warning here for anyone that's interested in this:  YAG lasers are extremely dangerous to your eyesight!  If you don't know what you're doing, don't mess with this or you WILL probably destroy the retinas of your eyes.

10

Projects, Designs, and Technical Stuff / Re: proper charging and discharging of dc-dc using mosfet

« Last post by xvr on Today at 07:48:38 pm »

I want to discharge the negative voltage to ground using NMOS.
Vg=5V and Vs=-2V so the NMOS is open.

When you 'close' MOSFET and set 0V to its gate you still have -2V on source, so MOSFET still open. Only when Source drops below Vth MOSFET will be closed.
This is a reason of -1V output.