CUSTOMER SENT ME A POWER SUPPLY BOARD TO TEST
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- Опубліковано 29 лис 2024
- Testing a customers power supply board. The smoke at the end is from the lamp with both elements of the lamp lit melting the rubber mat that it was sitting on. The Variac I am using has a built in isolation transformer. It is a sencore PR57. Here is a link to it. akdatabase.org/...
Here is the link to the original video from 2013 • Element Hisense Dynex ...
Clever use of the incandescent bulbs for a load. I might have come up with the same option.
Im glad you are back...you are by far the best tv repair man on UA-cam...i have learned alot from you....considering that i am almost 50 years old ...keep them videos coming...you are the champ :)
i have a clicker press with an end of life pcb..I got it fixed for about $80US.They changed a cap and a relay.I was very relieved they got it fixed .Its really a very old Italian made machine Atom G999..You Electronic guys are the greatest..sorry for my english im not a native speaker.Have an awesome day!
I have never needed to deal with a base load for the standby. However, it has been a common issue that the MAIN output ( 5 V because it provides the feedback ) has needed a minimum load. That has been listed in the data sheet. But generally that covers all worst case situations regarding line voltages and ambient temperatures. The data sheet specified value has been more than the necessary minimum load. Our experience has been that 50 to 60% of the specified minimum load has always worked. But definitely only occasionally does some power supply start without at least some load on the main output.
All switchers need a minimum load to operate. Sometimes an active load is built on the supply to ensure startup. Obviously that is not the case here. However, you can probably get away with a small load on one of the rails because it looks like they are all generated by the same switcher.
What I'm saying is that you probably could have put two lamps in series on the 24V rail and the entire supply would have come up.
Just a suggestion, not in any way a criticism. Good video, thanks.
You are probably correct. I am planning on ordering some high-wattage low-value resistors to accurately load the supplies in the future. Thank you for your support.
@@norcal715
You can probably pick up a power resistance decade box for not too much on eBay. Very handy for power supply trouble shooting and repair when an electronic load is out of the budget.
I can tell you without all of that testing what's wrong with that TV: ITS A HISENSE! 🤦♂️😂
I am in NorCal/Shingletown near Redding...My son has 1000W switching supply sodium lamp driver that delivers between 300 and 400V to the lamp for variable output. the unit runs on 220VAC supply but it was wired incorrectly, where ground got 1 of the 110V lines, and 1 of the line inputs got ground with the other getting 110V line as it's supposed to. the unit no longer works.
As expected the case (ground) has only 2 references to the circuit board. Each of the 2 only go from the ground plane/case through flat capacitors to each Line connection after induction coils but before bridge rectification, I know this to be for surge protection. This should not have caused a failure.
.
I was thinking that maybe driving the 220V lines with 110V (ground is referenced to neutral back at the electrical panel) may have cause the mosfet switcher to lock "on" instead of oscillating which would send solid current through the mosfet via one of the primary windings of the main transformer and burning it. I call it the "exciter" winding because the other primary winding gets constant filtered DC from the line input via a bridge rectifier. (actually they parallel two of them and heatsink.)
What else could be wrong?
P.S. they poured a black goop all over the board and components that melts at about 200F, how nice of them :-)
If you have any ideas, you can PM me because I don't get notifications to replies.
Great work as usual.
I had the cap problem in that power supply, took me three days of back and fourth on the chassis, I saw your video and bingo, it was fixed.
Of course, that was a few years ago .
thank you sir
Thanks! I saw some smoke there at the end...
the lamp was heating the rubber mat it was sitting on
Good video as usual. I'll be leaving it on for a while and looking for dry joints before sending it back though. Mounting in the chassis might also cause the issues that the customer has mentioned. I like your smoke machine with the bulbs and pad! Last supply I got in was from a Sami 46A650 (old but nice image) where the owner tried to fix the fuses that kept blowing by wrapping a dead one in aluminium foil. There was a short in the power fets, you wouldn't believe the damage that board suffered when he turned it back on.
Hey Norcal great video, its been a while since I seen a new video. Miss your very informative and professional skill trade videos.
OMG your back with new videos!!!
Just a safety issue. If all you're using is a plain variac, then you're NOT isolated. Variacs are autotransformers, there is only one winding. If any part of it connected to mains, the output is too. Not trying to get on anyone's case about it, just don't want folks to think a variac protects them. An actual isolation transformer is needed.
I am using a Sencore PR57 variac with built in isolation transformer. I will make a note of it in the description. Thanks
@@norcal715 That's a nice machine. I have an old Heathkit IP-5220. Lifesavers.
Is it true that if display panel is bad it’s useless to repair as cost of available is as much as a replacement tv
In most cases yes, if you can even find a display. Most companies do not supply them as a replacement part.
Smoke at the end of the video.
I noticed it too at about 9:37.
It's in the description. Melted the rubber mat I had it on.
@@norcal715 You need a proper anti-static rubber mat that won't melt so easily. :)
But was there fire ?😍
Sometime the 4.7volt need to be exactly 5.0 are something you may have intimated starting on the TV
NorCal715, You might wish to save some time and effort by recapping the supply. It's a cheap fix and prevents problems later.
I was going to get a HiSense , low cost , but CHEAPED-OUT ON ELECTRONICS ? I mean It isn't going to have Nichicon caps in it.🤣
No ESR cap testing or ripple test with a oscilloscope when under load?
Maybe at a future time
Helpful, fixing my TV now.
hello sir
what soldering iron do you use and what temperature
thank you
How did you have the power supply connected to get past the in-rush current needed by the bulbs?
Just connected in parallel to the bulb, and completely isolated from main supply or earth connections. the power supply is isolated and the variac is isolated also. Make sure to watch part 2 of this saga also. ua-cam.com/video/e5__hNFu0h4/v-deo.html Thanks for watching
It's my understanding that a variac does not provide isolation. Do you have some special power input arrangement?
Correct, a standard variac is NOT Isolated
The variac I have is a sencore PR57 and it has an isolation transformer built in as well as a variac. A standard variac transformer does not provide isolation. Here is a link to the pdf owners manual and schematic. akdatabase.org/AKview/albums/userpics/10007/Sencore%20PR-57%20Manual.pdf
great video. The resistor from STBY to PSON ...is that to limit current?
Yes exactly. just in case the manufacturer of the board didn't put current limiting to the relay drive transistor.
Thank you..
Yes i remember u had 2 tvs with the same problem in your shop
good memory
I had the same power supply and the 2 caps on the top corner 10uf 25v was dead
so smart
i see failed cap with out needs measure?how did did video maker miss it??
Where
Right. Which one? I will look at again.
I love ur watch.. 😁😁😁
replace parts from
www.boardss.com
Z
You say a variac provides mains isolation. Well they don't. What on earth, no pun intended, are you telling us it does for? You sound to be a dangerous person.
Read the video description it has an isolation transformer in it