nec 2571 is the optocoupler model
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Last edited by zape; 08-31-2018, 07:42 PM. -
Re: What is a typical diode voltage that saturates an optocoupler?
The datasheet says the diode voltage typical drop is 1.2V at 10mA. Maximum current is 50mA. As with all diodes, it's current that enables it, depending on the exact optocoupler you get, the saturation voltage for one unit can destroy another.
The transistor saturation voltage is 0.3V at 2mA. -
Re: What is a typical diode voltage that saturates an optocoupler?
1 have around 1v drop on the diod.
what Vce should I expect on the other end?
I suspect bad optocoupler because I have 10v Vce where I expected less than 1vComment
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Re: What is a typical diode voltage that saturates an optocoupler?
1) How is this opto being used/connected?
2) How much is the current on the LED side?
3) Read about how to read data sheet, look at CTR: https://cdn.badcaps-static.com/pdfs/...85b94d258d.pdf
http://electronicsbeliever.com/opto-...r-explanation/Last edited by budm; 08-31-2018, 11:11 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Re: What is a typical diode voltage that saturates an optocoupler?
1V is probably 'off' though at cusp of turning on. You need to measure current through the diode somehow to really know how far 'on' it is.Comment
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Re: What is a typical diode voltage that saturates an optocoupler?
the diode current is 0.15 mAComment
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Re: What is a typical diode voltage that saturates an optocoupler?
0.15mA? That can't be right, the Ice will be low also so the Transistor will not be saturating. What is the Voltage source and how is the LED side is driven?
That is very very low, no wonder the Vf is only 1V. If you look at page 8 the Graph of Forward current VS Forward Voltage you will see what the Vf will be at around 0.15mA, about 1V @25c
What kind of circuit are we dealing with here?Last edited by budm; 08-31-2018, 11:23 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Re: What is a typical diode voltage that saturates an optocoupler?
The led is powered by 3.3v stby pulling down to ground via transistor and 470 Ohm resistor (that's how I measured the LED current). But I now checked the 3.3_stby voltage and it drops to ~2v when I try to power on the PSU!
So I think the problem is not in the optocoupler but in the Vstby source.Comment
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Re: What is a typical diode voltage that saturates an optocoupler?
It will help if you tell us what kind of power supply you are working on and also provide good clear straight shot pictures of the top and bottom side of the board.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Have an A2141 which is reading about 5.2V 0.07A on all USB jacks, started doing the measurements.
PPBUS_3GH diode: measures good .45V
PPBUS_3GH Voltage: maybe not so good 12.25V maybe bad T2? Unit did not come up in DFU on configurator.
The weird so far is
PP3v3_G3H_RTC_X diode: .104V (WTF?)
PP3v3_G3H_RTC_X voltage: 3.39V (Normal)
Stopped there attempted reverse voltage injection at PP3v3_G3H_RTC_X with 1V. Instead of the circuit sinking any current, My PSU suddenly reads 3.4V with no current draw.
Not sure what any of this means... -
This is my first attempt at troubleshooting a board like this, I know I could just buy a new board but I'm curious to figure out how this works. I've been testing different components in the evenings this week and I think the problem is with the IC failing to start up for some reason. When the board is plugged in there is no standby voltage.
Then today it randomly sprung to life like a zombie but shortly died thereafter. I have no idea why it would have done that and its the first time I've seen it running. I discharged capacitors on the board last night, then it was sitting today.... -
Hello friends,
Looking for some guidance here. The RAM voltage circuit on this motherboard keeps burning out PU301 which is a RT8231AGQW. Copy of the board with the burnt chip attached with some voltage measurements and copy of the schematics also included.
I think I've checked almost every component in the circuit, but when I change the RT8231, the laptop starts I have 1.2V on the inductor for about 10 seconds and then the RT8231 goes south and no more voltage on the inductor. All other voltages on the laptop are good, this is the only one conking out for a reason I... -
i have Gigabyte Z490 Gaming X Motherboard .it has a power on no display fault .. no vcore voltage and debug led stuck CPU LED .
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VCCSA Voltage OK
VCCPLL Voltage OK
Ram Voltage ok
RamVTT OK
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But No Core Voltage
and i want to this vrm ic datasheet or pinout (ISL69269)
anyone have this ic pinout voltages?...06-25-2025, 07:19 AM -
Hi Everyone, I am new to this forum. I have a Panasonic LED TV which doesnt turn on and is blinking 4 times repeatedly when I turn on the switch. The TV does not respond to the remote control so I had to turn on using the physical switch on the side of the TV. When I turn on the switch the 4 x blinking starts and repeat itself until I turn off the TV. There is a black screen. I turned off the light in the room to check the panel and I think there is no backlight as far as I can tell.
I have been inspecting and testing the capacitors and diodes in the power supply board to try to...
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