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Fluke-196B Software and power adapter.
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Lachin012:
Hello, so can someone tell me what dB means and for what purposes is it needed?
mahi:
Lachin012: I could open the power supply again and measure the dimensions but I'm not really sure what it is good for. You can't get the Fluke enclosure so what's the point of making the PCB the same size? If you really want to replicate the circuit, get the components, find a suitable enclosure that will fit everything and design a PCB for that enclosure. But honestly, I think you are over-complicating things. You get noise from your switched-mode power supply. Just replace it with a transformer-based one (admitted, these may be harder to find nowadays as pretty much all power supplies are SMPS). If you want to make one yourself, build a circuit around a transformer, full-wave rectifier, 7818 voltage regulator and some smoothing capacitors: Example circuit.

Decibel (dB) measurements are voltage measurements on a logarithmic scale and are useful to determine gain and loss (e.g. 3dB gain). There are two modes: dbV and dBm. dBV is a decibel scale relative to 1 volt (1V = 0dBV) and dBm is a decibel scale relative to 1 milliwatt in a 600 ohm impedance (0.775V = 0dBm). The latter is a common unit in audio measurements. Other common impedances are 50 and 75 ohm. Some multimeters allow the user to set a custom impedance for the dBm measurements but I don't think the Fluke Scopemeters support that.
Lachin012:

--- Quote from: mahi on November 01, 2022, 11:12:48 am ---Lachin012: I could open the power supply again and measure the dimensions but I'm not really sure what it is good for. You can't get the Fluke enclosure so what's the point of making the PCB the same size? If you really want to replicate the circuit, get the components, find a suitable enclosure that will fit everything and design a PCB for that enclosure. But honestly, I think you are over-complicating things. You get noise from your switched-mode power supply. Just replace it with a transformer-based one (admitted, these may be harder to find nowadays as pretty much all power supplies are SMPS). If you want to make one yourself, build a circuit around a transformer, full-wave rectifier, 7818 voltage regulator and some smoothing capacitors: Example circuit.

Decibel (dB) measurements are voltage measurements on a logarithmic scale and are useful to determine gain and loss (e.g. 3dB gain). There are two modes: dbV and dBm. dBV is a decibel scale relative to 1 volt (1V = 0dBV) and dBm is a decibel scale relative to 1 milliwatt in a 600 ohm impedance (0.775V = 0dBm). The latter is a common unit in audio measurements. Other common impedances are 50 and 75 ohm. Some multimeters allow the user to set a custom impedance for the dBm measurements but I don't think the Fluke Scopemeters support that.

--- End quote ---

Thank you for the detailed answer, I have already ordered everything for the transformer power supply, I want to make it as close as possible to Fluke, and therefore I wanted to know approximately the dimensions of the printed circuit board, I will find the case is approximately the same as Fluke's own, maybe a little more, but I need the dimensions of your printed circuit board, if it’s not difficult for you to open your power supply and take the dimensions of your board, I will be very grateful to you. I don’t particularly want to make third-party circuits that can harm my device, so I will make the same block power supply as per the scheme, then I will post a photo here of what happened, thanks.
Lachin012:
I don’t want to offend the author of the circuit, thanks to him for the circuit, but it seems to me that there is an error in the circuit, namely the TL431 control, maybe I’m wrong, but the resistive divider should be on the control and not on the cathode.

Could you confirm on the board is TL431 or TL432? maybe I'm wrong about something.
mahi:
Lachin012: The size of the PCB is 89x57 mm.

I looked at the SOT-23 package under a microscope but I have a hard time reading what's printed on it. It's clearly ending in 31 (not 32) but the first digit is very poorly etched and hard to read. I think it's a 4 so that would make it 431. A simple diode test seems to confirm it's a TL431 as determined by asis. I did a quick check of the connections to the nearest components and I do believe it's drawn correctly in the diagram.

Pay attention to the resistor values. The red values are measured in circuit and not the true value of the component. The 4-digit code is the proper SMD resistor code.
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