Agent24 said, there are weird ways the switcher can fail, but haven’t seen this. So check the power input pin and see if the voltage drops to the switcher. Other than that, either the ultrafast rectifier diode, something is wrong with the feedback, the caps for that 5VSB on the output, maybe there is a starter cap on the primary. There isn’t anything else much… besides the motherboard is drawing too much power.
Read the spec sheet. VDD needs to be 12VDC to start and 6V or below it stops....
CapLeaker
Leaking Member
Last Activity: Today, 10:30 AM
Joined: 12-04-2014
Location: Atlantic Canada
-
Same here. Those tariffs suck.
...
Leave a comment:
-
I’ve seen these LNK, TNY, TOP etc. switchers do weird things, but not that. Usually the secondary output voltage is pretty much bang on too, but here not so much. Makes me wonder about the feedback circuit.
Leave a comment:
-
Not sure what to think. Are you measuring the caps when they are still hot or warm? Because that affects the ESR reading and a bad cap can look good again as long it it warm. They need to be measured at room temperature.Leave a comment:
-
Good question. It’s rather maximizing the bang for my buck. Things are rediculously expensive thanks to some government decisions and being taxed to the hills.
Leave a comment:
-
Not sure if I should buy one or not. I like to have another ESR meter. Not sure if I should buy another Agilent / Keysight one or on of these cheapo jobs.Leave a comment:
-
Preheater and good flux, that’s all you need.Leave a comment:
-
Oh boy! That’s not nice to trace with. If you do see a, electrolytic capacitor in series with the audio (DC blocker) check the audio going in on one side and the audio going out of the other side too. If the audio isn’t equal, replace that cap.
A headphone only has 3 wires. A audio left and right and GND. That’s it. You check between GND and the other 2 (left and right audio).
if you go backwards from the jack, I think it goes like this: jack, lowish ohm resistor, a dc blocker cap and audio amp. Find that dc blocker cap and check the audio there. Whatever the problem is, it...Leave a comment:
-
Yeah… putting a socket on a HV chip isn’t such a good idea. But then these TNY, LNK, TOP, etc devices like this die like flies anyway. As long as things are hospital grade clean around that chip after replacing, you should be fine until the dust builds up between the pins. Had seen a replacement fail within 24 hours, only because he didn’t clean good enough after the first repair. I did the second repair and all is well.Leave a comment:
-
All we are looking for are 3 things. Number 1 is obvious being DC voltages. Number 2 is data flow and 3 is oscillators oscillating.
Settings on the oscilloscope are a factor, otherwise you don’t see anything. I suggest you watch some tutorials on how to use an oscilloscope and get familiar with its settings and how to reset it just in case you bugger the settings up.Leave a comment:
-
Sounds like something is open or dead shorted. Did it quit all of the sudden or loss of volume over time?Leave a comment:
-
I made some green highlights around the chip to poke around with the oscilloscope....
Leave a comment:
-
That block diagram isn’t much good here, as it tells you how are things connected, but it still leaves the display out. So… in a situation like this you have to start somewhere. And the first thing to do is to check that power is getting to everything where it needs to be. After that it’s probing around with the oscilloscope. Start with the PIC IC and see what you see. Look at the SPI data line, voltage, clock, etc. My guess is that something is dead. That schematic is a pain to look at on my little iPad as I constantly need to zoom in and out and move the page around.Last edited by CapLeaker; 09-04-2025, 06:06 PM.Leave a comment:
-
Check ALL capacitors on this unit.Leave a comment:
-
I think you got lucky there. Usually DSP’s including this one are programmable....Leave a comment:
-
What happens again to the FP pin and the stby voltage, if plugged in to the main board and power mains, but not turned on, then another measurement with the computer running?Leave a comment:
-
This block diagram is somewhat helpful, but said nothing much on what we need. We know now how the boards are connected and talking to each other. But as far as the display goes there is nothing.
Under a Block Diagram I understand this: see attachment.
This block diagram is for something else, but you get the idea once you see it....Leave a comment:
-
Yeah, that’s due to the light bulb trick as it limits the current. Since nothing blew up you can take the lightbulb out of circuit. Anyway, the main principle is the PSU kinda works and the board POSTs. You know that the supervisor IC is shutting things down for one reason or other. Let it be due to bad capacitors or itself being bad. It doesn’t like something. If you want, search for my name and for a thread I started with a Powerman IP power supply a while back and read it. Ended up being the main filter cap dry.
Anyway all the power rails must be on, because otherwise it wouldn’t...Leave a comment:
-
Could be… but stil… for a cheap board, why creating yourself a headache. This story would be different, if there are no replacement boards…
But for a $50 board, not worth the hassle.Leave a comment:
-
Install a jumper between FP pin and GND (disables fault protection) turn on computer. Be very careful with this trick and don’t run the board like that for a long time. Just see if it will post.
The 2V isn’t enough drop for the opto to turn on and enabling the primary to turn on. I am guessing there is a bad cap somewhere, might be even the main filter cap on the primary.Last edited by CapLeaker; 09-03-2025, 09:41 AM.Leave a comment:
No activity results to display
Leave a comment: