Not necessary. I have been designing electronic, not repairing it and I am not a switch mode power supply expert either. This may make it difficult to find the fault.
The next problem is if some exotic chip or transistor is gone, it might be difficult to get a replacement.
There first place where I am going to look there is stuff like LM358, 7815, 7818, TOP244Y (Assume it matches the service manual) they are easy enough to replace (But there will be some delivery time on the last one).
But it worries me that the LCD has a quick flash a bit before the error message. I could be nothing or it could be that when the main switcher is enabled all voltages sags due to a short in the output circuit.
As for me it is all about time, if there is need to repair something i’m not familiar with - it usually takes much time.
And sometimes it is more simply and cost efficient just to buy new one, and play with new toy).
And put the old one away until passion to repair it would come)
I do agree with that, but this power supply is a bit on the expensive side: 20V/50A or 60V/20A with full computer control, is not the average small lap power supply.
That is common for SMPS with a few thousand hours runtime, cheap capacitors and running hot, I do not believe that applies here (I do have an ESR tested). Often you do not even need an ESR tester, you can just look for capacitors where the top has a bulge.
By looking at the display I can tell you have an AIMTTI QPX series power supply. What caps are used in that series, I mean what brand? In more mainstream series it is known the caps are not top-brand which one would expect due to price.
That is correct, you could also have seen that from the service manual I linked.
I did peek into it when I got it, but I have forgotten all about what capacitors was used. The supply is only a few years old and has not been running at high temperature, i.e. it is very unlikely that there is a problem with the caps.
I got the lid off. The capacitors are from Vishay and Elna.
The problem was easy enough to find, but I have not figured out how to fix it yet.
The mains switcher has an internal 24V switch mode power supply, this power supply cannot deliver stable 24V but pulses. Is this because it is overloaded due to a fault somewhere or is the switcher IC bad?
One way to check is to use an external 24V lab power supply and see how much current is drawn, but I have to be a bit careful because everything is mains connected.
It looks like the service manual is mostly correct, but there are differences.
If it is something that draws to much current when feed 24V from a PS, it will probably be easy to find with the thermal camera or maybe I can just look after the smoke.
That test with the 24V PS will have to wait a few day until I get the new PS, my small test PS can only deliver 12V and my other PS's are busy.
I just looked up the price of that thing, no wonder it’s a BAD day!
Too bad the picture you posted is such poor resolution. I was hoping to do reconnaissance flight over the landscape motherboard to see if I could find anything obvious.
Have you thought of contacting the company that makes this power supply, to say “I have been using this product, and I publish extensive and widely followed electronics tests online — here is a link ….” and asking them if someone there might help you troubleshoot it, or if they have a recommendation how to proceed?
I’d think it might be they’d respond by giving you a break on out of warranty help, or perhaps a loaner or a donation replacement.
(I’m thinking of LEDMuseum in Seattle, where Craig, who has been reviewing LEDs since 300 baud, has been gifted some hardware over the years by companies that have recognized his contributions)
Not really. If my website was about test & measuring equipment it was a good idea, but when I write about something else, I do not believe it will work.
That photo is a little better, but not good enough.
With desktop computers it is amazing how often just re-seating cards or unplugging all cables and plugging them back in works. Even though there would seem to be a physical connection, with time things happen.
I notice that the heat sink for the 7815 looks like it just clips on. Maybe that is just the pic, usually the sink would be soldered to the board for stability and the component screwed to the sink.
Hot and cold cycles can literally, through thermal expansion and contraction, cause “creep” and physical connections can loosen.
Also there is the possibility that the temperature monitoring circuit only “thinks” it is over heated. I think that is why you are are already zeroing in on that part of the board.
I suggest removing the PC board and checking for bad solder connections underneath. Reheat the solder pads for the transformers just in case. Check the ESR for all the electrolytic capacitors.
