Recent Posts

1

Other Equipment & Products / Re: Different bases on Amscope microscope

« Last post by HobGoblyn on Today at 03:57:13 pm »

There’s a few YouTube vids saying to avoid the articulating ones at all costs

For example

https://youtu.be/dFdrTsDIw24?feature=shared

2

Repair / Re: Help needed for repair of Efratom FRS-C rubidium oscillator

« Last post by edpalmer42 on Today at 03:56:55 pm »

One complication to keep in mind is that the input to the U39 module is high voltage DC rather than AC.  I don't know if typical AC switching power supplies will tolerate high voltage DC input.  You might have to rearrange the input power to feed them with AC.

The conversion from AC to DC is done with a straightforward rectifier. That rectifier should be able to deal with momentary mains peak voltages, so I would expect it to be ok, no?
And if the replacement power module has AC input, it can also be hooked up tot he AC line coming into the box.

It isn't clear to me why a switching supply would have trouble with high-voltage DC input.  The only thing I can think of is that with DC, the input voltage won't ramp up at mains frequency, it will just hit hard at maximum voltage.  Maybe the internal surge limiter wouldn't be able to cope with that.   

Cheers for now, variable supplies are ordered, I will report back once I have rigged up the whole shebang.

Good luck.  Let us know how it goes.

Ed

3

Networking & Wireless / Re: RESTORING EXTERNAL USB HARD DISC.

« Last post by magic on Today at 03:56:27 pm »

recover data even when you deliberately tried to remove it -- even after filling all the free space on the FS with a dummy file.

No way. It only works on files whose data blocks have not been overwritten.

4

Beginners / Re: buying a oscilloscoop

« Last post by pcprogrammer on Today at 03:55:55 pm »

iam not a expert or even a amateur like you guys. i work with elderly people thats my day job ,this is just my hobby nothing more
i think the 300 euro scope is good enough for me ,dont see the need for 4 channels and more options etc like the 500 euros scopes and up
i found a commodore 1901 monitor for 15 euros working just needs some love ,more projects 

Based on this my advice would be to buy a cheaper portable hantek or even owon like this one: https://eleshop.eu/test-measure/oscilloscopes/all-oscilloscopes/owon-hds272s-handheld-oscilloscope.html
Gives you more functions in one device, is cheaper and will do the things you want while fault finding in old computers and monitors.

No need for 12 bits in your case. Sure it is more accurate, but won't aid better in finding faults. 8 bits is plenty for your use cases.



Adrian used the Hantek version in the above video, and he can make his repairs with it.

5

Repair / Re: Sony J30 PSU repair

« Last post by john2021 on Today at 03:50:13 pm »

The second controller markings are hard to read, but I believe it is ST L6574D.

The last measurements were with B3 installed.

I said I had took out the rectifier schotcky diode TRANSISTOR FCH30A04 on the secondary side, so there will be no load there.

6

Microcontrollers / Controlling LED with a button

« Last post by Tadeuszh on Today at 03:49:33 pm »

Hi there,
so I have a simple problem, I am trying to controll the LED with a button. I want it to flash when the button is set, and darken when it's on reset. I've used the TogglePin function, and it doesn't work. It changes the LED state and leaves it as it is. I've tried removing the else statement cauze I thought it might be enough for one if to be written - but when i did, it crashes. I mean it works but once it lights up, the communication between button and LED breaks and clicking the button doesn't change the LED's state. I have to mention that it is supposed to be controlled by ISR. Any advices what do I do?


void ToggleDiode()
{
       if (HAL_GPIO_ReadPin(GPIOA, GPIO_PIN_5) == GPIO_PIN_RESET)
       {
           HAL_GPIO_TogglePin(GPIOA,GPIO_PIN_7);
       }
       else
       {
          HAL_GPIO_TogglePin(GPIOA,GPIO_PIN_7);
       }
}

void handleButtonInterrupt(void)
{
   ToggleDiode();
}

7

Test Equipment / Re: Keithley 2231A-30-3 Communication

« Last post by BennoG on Today at 03:48:35 pm »

Be also aware that the RS232 output uses the same ground level as CH3 output.
So I put also a isolator in the USB-RS232 converter (there is 5V on the 9 pin sub-D to supply the psu part of the logic)

P.S. I figured a way around the slow communication, see my other post in  on the 2231A, including C# source code and a nice HMI you can use to click on.

Benno

8

Other Equipment & Products / Re: Different bases on Amscope microscope

« Last post by KE5FX on Today at 03:47:58 pm »

You want an articulating boom.  Those fixed stands suck.

9

Projects, Designs, and Technical Stuff / Re: 120V AC power path for solar charge controller

« Last post by davegravy on Today at 03:46:51 pm »

I like the simplicity but doesn't this have the same issue due to the fact the panel can be higher voltage than than the AC source even when it's not actually sunny, (ie can't provide meaningful current)?

I measured my panel Voc face down on the floor (almost no light condition) and it's higher than I expect to get from the AC source. I expect voltage drops sharply as soon as any current is drawn in this condition, but does that then lead to oscillation where the MOSFET turns on, voltage drops, MOSFET turns off, etc?

10

RF, Microwave, Ham Radio / Re: 120 or 125 ohm coax

« Last post by tchicago on Today at 03:41:52 pm »

Plumbing tubes and pipes have standard dimensions, with 3 grades of wall thickness
Engineering ToolBox:  "CTS-CopperTube Sizes"   "NPS-Nominal Pipe Size"

My biggest issue is the inability to bend the thicker pipes. It was kind of OK to bend the thinner "refrigeration" copper pipes, but those thicker ones - I have no idea how to do that without special equipment.