I have a PSU where some of the output filter caps are a tight fit, and it would help the crowding a lot if I could install a couple of the new caps about 1" above the board. Would this make the leads too long? I can solder 16 gauge wire to each lead to reduce the inductance, if it will help. Of course, each lead will be covered with heatshrink to prevent shorts.
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Re: How long can cap leads be?
i have done 1/2 in when 12.5 mm caps wouldnt clear stuff on the board.some psu use 10 or 8 mm caps.no harm done. -
Re: How long can cap leads be?
The switching frequency is only ~100 KHz, and there's already inductance (either stray or part of the circuit) in series at most locations on the secondary side where large caps are usually found. A few pH/nH additional in series won't make a difference.
Exception(s) to this are the small bypass caps next to the switching controller IC or on the output side of 78xx/79xx 3-terminal regulator(s) - these have to have very short leads to avoid instability/oscillations due to high loop-gain linear circuits.Comment
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Hello,
Today I discovered that PSU Chieftec BDF-750C PSu has died. Not sure when that happened since I didn't use PC for a long time. PSU is not that old, about three years, but just out of warranty.
I had some previous success in repairing different electronic devices including PSU. Until now, the problem was usually bad electrolytic capacitors after many years of operation, but this time is different. When trying to turn on the PC, fans move a little bit and then nothing. There is astable 5V SB (actually 5.13 V DC Standby voltage), but that's it.
I tried to jump start... -
Hi all! I'm a newbie to to the forum and electronics repair in general.
I picked up a nonfunctional ASRock Taichi X570 motherboard that someone threw away. My main goal is it to repair and use it. But even if it's not possible, I'd like to learn about the process.
I'd very much appreciate some guidance.
Here are the steps I've taken to diagnose the board:
I first tried powering the board without a CPU or memory. The lights turned on. As you'd expect, the board wouldn't boot.
Hoping the board worked, I bought a compatible CPU on amazon. I wanted... -
Hello guys,
I have a problem with my laptop as in the title, black screen, capslock displays error code 5 long 3 short, no voltage on the coils above the CPU, before removing the drive I had 0.8v there, power led flashed 5x long and the battery would not charge (current jumped from 0.5a to 2.8a), now on the power led I have a steady white light or orange when the battery is connected.
What I did:
- Laptop was not detecting ram, loose pins on ram slot, error 3.2 disappeared, ram working tested in another laptop
As far as I know the laptop was in another service center... -
Edge lit LED TV has 1/4 section backlight out. Replaced the LED bars and sharing the findings on the original 10k hour LED bar.
These are 6V LEDS (reads ~5.4+ on my LED tester) New bars read about 147V per 1/2 of each bar. Clearly original LED bar has some problems- One section is 153v with a dead LED so clearly built up resistance
- One section flickers but magically fixed itself after driving individual LEDs. All done with an LED tester so don't know if would work driven by PSU backlight circuit and how long it would last
- Connector pin to test pad resistance is nearly 0 ohms.
07-07-2025, 12:18 PM -
Problem
This is an LG edge LED lit LCD Display. The LEDs are on the bottom edge of the display. There are 2 bars (left and right) Each bar has many LEDs and a 6 pin connector. Each pin drive several LEDs thus is the highest current flow / heat junction. The weak lead free solder gradually fails with thermal expansion/contraction cycling and increases resistance. PSU will compensate up to a point, then when the current is too high, PSU just shut down the backlight causing a dark display. I have even seen one which the connector just fell off as solder points became completely detached....
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