03-02-2018, 03:45 PM
There are many switched-mode power supplies that manage without an opto-coupler for feedback. Using one should result in better regulation of the output voltage, but for non-critical applications, other techniques are adequate. But I've never seen an ATX power supply without an opto-coupler, so if this mystery supply doesn't have opto-couplers, then it's even less likely to be an ATX type...
For avoidance of doubt, the acronym "ATX" refers to a particular form-factor used by PCs. The power supply specification is a sub-set of that - more here: https://en.wikipedia.org/wiki/ATX - so I really doubt that this boombox incorporates an ATX PSU.
Including a link in a post is as simple as just typing it in. Using copy-and-paste is more convenient and less error-prone. There's no special procedure needed. At the risk of teaching you to "suck eggs", simply return to the thread on UKVRRR, click on the web address and press Ctrl+C. Then back to GVR, and paste (Ctrl+V) in the message. If you prefer, right-click on the web address and choose "Copy" from the menu that pops up, and then when you're typing the message back here, right-click followed by "Paste".
In the meantime, I will say that switched-mode power supplies are extremely complicated beasts, and no-one I know has a 100% success rate with them. And I'm talking about people who specialise in repairing them. They are a bit of a special interest for me, and I run a 4 day course about repairing them, but despite that, I reckon I can only fix "most" rather than "all" - a success-rate of perhaps 80-90%. And that's with the thing in front of me - not remotely via a forum. So in short, it might help your sanity with this sort of repair job to swallow a healthy dose of reality - part of which is learning to turn down these sorts of repair jobs.
You can download an old version of the notes for my course here: https://www.dropbox.com/s/sjswuzqxbkanw2...s.pdf?dl=0 - ignore the numerous typos - it's been updated a lot since this version. It obviously has a broadcast bias, and covers a lot of basics that you can almost certainly skip over, but it's a fairly readable introduction to the topic with minimal maths. With power supply repairs, the only way to improve your success rate (and personal safety) is to understand how they work and what typically goes wrong. Note that there is a section in there entitled "When not to attempt a repair"!
The final thing to say: is this power supply definitely faulty, or is it being pulled down by a fault elsewhere? Have you tested the power supply in isolation (into suitable dummy loads), or have you tested the rest of the unit using external power supplies? Sorry if these are obvious questions, but there's no point getting into the specifics of the PSU until we've answered this.
For avoidance of doubt, the acronym "ATX" refers to a particular form-factor used by PCs. The power supply specification is a sub-set of that - more here: https://en.wikipedia.org/wiki/ATX - so I really doubt that this boombox incorporates an ATX PSU.
Including a link in a post is as simple as just typing it in. Using copy-and-paste is more convenient and less error-prone. There's no special procedure needed. At the risk of teaching you to "suck eggs", simply return to the thread on UKVRRR, click on the web address and press Ctrl+C. Then back to GVR, and paste (Ctrl+V) in the message. If you prefer, right-click on the web address and choose "Copy" from the menu that pops up, and then when you're typing the message back here, right-click followed by "Paste".
In the meantime, I will say that switched-mode power supplies are extremely complicated beasts, and no-one I know has a 100% success rate with them. And I'm talking about people who specialise in repairing them. They are a bit of a special interest for me, and I run a 4 day course about repairing them, but despite that, I reckon I can only fix "most" rather than "all" - a success-rate of perhaps 80-90%. And that's with the thing in front of me - not remotely via a forum. So in short, it might help your sanity with this sort of repair job to swallow a healthy dose of reality - part of which is learning to turn down these sorts of repair jobs.
You can download an old version of the notes for my course here: https://www.dropbox.com/s/sjswuzqxbkanw2...s.pdf?dl=0 - ignore the numerous typos - it's been updated a lot since this version. It obviously has a broadcast bias, and covers a lot of basics that you can almost certainly skip over, but it's a fairly readable introduction to the topic with minimal maths. With power supply repairs, the only way to improve your success rate (and personal safety) is to understand how they work and what typically goes wrong. Note that there is a section in there entitled "When not to attempt a repair"!
The final thing to say: is this power supply definitely faulty, or is it being pulled down by a fault elsewhere? Have you tested the power supply in isolation (into suitable dummy loads), or have you tested the rest of the unit using external power supplies? Sorry if these are obvious questions, but there's no point getting into the specifics of the PSU until we've answered this.
