Recent Posts

1

Test Equipment / Re: Who is the OEM for this PSU? Multicomp MP711057

« Last post by Hydron on Today at 01:19:24 pm »

Uh if the noise isn't an issue, then given the 60V/10A/300W version (and also the 30V/10A/300W model after discount at checkout) is only a hundred quid (VAT inc.) on amazon, why even consider aliexpress (which will charge VAT ontop of the headline price) with it's extra risk and lack of return option?

2

Projects, Designs, and Technical Stuff / Re: Help with DIY guitar pedal

« Last post by CaptDon on Today at 01:14:27 pm »

On a board like that the capacitor should not even get warm!!!! You have the cap in backwards or the power hooked up backwards!!! I would guess all of the I.C.s are probably shot. Probably time to shit can the thing and by a new one and carefully assemble starting from new. The unit you have is so hacked up by now it may never stand a prayer of working. The cap running hot tells me this thing is totally done for and you need to really decide if this project is within your skill set.

3

Projects, Designs, and Technical Stuff / Re: Emergency stop for runaway large DC motor

« Last post by CaptDon on Today at 01:08:19 pm »

Remember this very important safety item. If you sense overspeed the fault circuit must latch itself to prevent re-applying power when the RPM slows below the trip point during braking!! The circuit should be wired to self latch until manually reset!!

4

Test Equipment / Re: New Hantek DSO2X1X models?

« Last post by coastline8888 on Today at 01:04:50 pm »

Thanks David. 

I misunderstood vistorik.

I read "can, not should" to be a warning not to!

I have read further into the thread and now understand (hopefully) the 3 types of update files:

• 3209_B209 - updates firmware only (not software)
• 2024.03.26 - updates software only (not firmware)
• 2024.03.26_fpga_3209 - updates both firmware and software

So I'll use "2024.03.26_fpga_3209" to update to the latest firmware and software.

5

Beginners / Re: Put LC filter before or after LDO?

« Last post by Nominal Animal on Today at 01:04:45 pm »

for a typical +5V rail of a USB outlet, some spec says 10uF is the max capacitive load

Yes, as Manul wrote above.

If one wants their USB device to work with all sorts of USB hosts, then 10µF input capacitance should not be exceeded.
That does not mean that higher input capacitances won't usually work.

Surely I've seen much bigger caps on the input of USB devices.

Me too.  In fact, for very power hungry devices on tiny SBCs (where the USB bus voltage is the internal 5V rail), extra capacitance can add stability.  For early 3G USB 2.0 modems having exactly such issues, Olimex created USP-CAP, with 2000µF bulk capacitance between USB +5V and GND.

However, using such a device will surely trip the overcurrent protection due to initial inrush current on most modern desktop and laptop devices.

6

EEVblog Specific / Re: EEVbog 1613 -Audiophile REPAIR: Chord Hugo DAC

« Last post by coppice on Today at 01:04:29 pm »

I think i know why the battery was acting weird:

You damaged the insulation on the battery negative cable close to the wifi module when you used the yellow plastic spatula at 10:20 in the video.
I have a big screen and can see individual strands of silver wire starting at 10:46.

It also looks like you damaged the insulation on the positive wire when you pinned it down with the tweezers at 11:17, i can see a silver spot in the middle of the cable at 10:22.
While doing this you might also have produced a short between the positive wire and the through hole pad below it, which would have triggered the protection circuit. After you let go of the wire the short was removed and the battery protection circuit could recover.

At 12:15 i can count three strands of wire in the negative cable, i attached a zoomed in screenshot to this post.
I can also see some silver in the red cable.

I was puzzled that he took out the batteries and then desoldered, but put the batteries in before soldering the contacts. I would have soldered the contacts with the batteries out, giving me lots of room, and then slipped them into place.

To be fair, if you solder with batteries outside, you then may find that wires are of the wrong length or you need to bend them awkwardly.

He did have a role model for lengths that would work well in the batteries he took out.

7

Beginners / Re: 5V buck converter debugging

« Last post by davegravy on Today at 01:03:05 pm »

The Webench design (link) shows a 412kHz Fsw

The simulation link no-worky.

I tried WEBENCH using the highlighted part   LM64460CPPQRYFRQ1   
and it won't accept less than 6 V input.

WEBENCH also claims "simulation not enabled for this design"

So how did you get it to simulate to get the 412KHz Fsw ?

Strange, I used the "share public link" feature in Webench.

My design also says "simulation not enabled for this design". I assumed that TI has not programmed simulation capability for this IC, similar to how they don't have SPICE models for all their ICs. Do you think instead this is a sign the design is bad?



This is where I got the Fsw = 412KHz from, under "operating values"

Indeed I'm not operating at 16V, it's designed for a minimum of 8V input, but I can't get to 8V due to the massive current draw (and resulting IC failure) at anything above ~4V.

8

Beginners / Re: how can I measure AC voltage of bridge diode on PCB of CRT TV?

« Last post by CaptDon on Today at 01:02:29 pm »

If you want to measure the A.C. input voltage to a bridge rectifier wouldn't simple logic tell you to place your meter across the two A.C. input terminals of the rectifier?? And likewise to measure the D.C. output of the bridge you would measure across the + and - output terminals. You better be using a battery operated meter if you are probing around in the hot side of the SMPS. And be aware that on the output side of the SMPS the switching frequency could be 20KHz to 50KHz and switching waveforms in that area require an oscilloscope. Be careful and don't take any measurements in the hot side of the supply with equipment that is grounded (like a scope) unless you are using an isolation transformer to feed the device under test.

9

Other Equipment & Products / Re: Pace TT-65 cleaning

« Last post by Shock on Today at 01:02:04 pm »

You didn't say if you swapped the tips around or measured them with a caliper etc.  As mentioned above, it could possibly be a burr on the set screw hole (screw that fixes the tip in). In that case you might be able to knock the edge off. Take a look in the hole or on the outside of the tip for abrasion marks see if you can deduce where it's catching.

I suspect though the former owner may have been using just one side of the tweezer to prep boards or something and allowed oxidization to build up in the second heater. There is a cheap heater on ebay at the moment, check if you need one with a sensor first if you intend to replace it.

Just don't clean or try lubing it with anything that bakes on otherwise if it polymerizes it will be a complete headache.

10

General Technical Chat / Re: Is there a meaning to colors on a transitor?

« Last post by Psi on Today at 01:01:43 pm »

Yes, its just the part number without the prefix, like 2N etc..
Colors are the same numbering as resistor colors. So red red red red would be 2N2222 etc...


https://www.instructables.com/From-Resistors-to-ICs-Color-Codes/