That line voltage switch brought back memories, I used to repair PC power supplies, hundreds of them, it was quite common to find them blown up with the AC voltage switch set for 110VAC so we'd disconnect and insulate one of the wires to the switch then cover the selector up with a warranty sticker. We never got a return because the 110VAC setting wasn't working. Looks like a real old school design too with the TL494, that used to be a real common SMPSU controller chip in the '286 PC days and before.
Such a pain to get out the board to diagnose it! But that unit seems to be one of the better designed low cost/high current supplies available from China. The one pre-service test I ALWAYS do on such supplies is monitor the output voltage transient after switching the unit on and after switching it off - especially on a light load. It is certainly not designed to supply a constant 30A, but it might also have been quite interesting to run it up to 30A for a very short while and look at the component temperatures. Nice work Peter!
Nice job! I like your methodical approach. I too have gone through circuit components and have found basically nothing wrong, only to clean up some poor solder connections - possibly even from manufacturing - and had equipment come back to life. I see that more often with kits, or on previous repair attempts. I think my least successful repair attempts have been on switching power supplies. Thanks for sharing your video and workbench!
In stead of desoldering the diode pack, you could have checked it in circuit using a resistance meter that is not based on a DC measurement (which goes for most multimeters) but that is based on an AC measurement. You can find those in so called ESR-meters which are often used to measure the resistance of capacitors. Because these ESR-meters use a frequencey of e.g. 100 kHz, any coil in parallel with a semiconductor will have a very high impedance. The resistance the device measures will then mostly be that of the semiconductor.
I know this idea, but it is not practical as the low impedance you measure can be everything, the transformer winding or a partly defective diode, so at the end no valid and useful result.
I was watching the video. I was all interested in it and then a heard a beeping. I had to pause and stop a second because I thought it happened in my own home. I then backed up the video and discovered it was something beeping in the background of your video. LOL. Good video as always.
Even though I would be haPPy to own this power supply, it really makes you aPPreciate well designed & manufactured units. Thank you for the video Cheers from So.CA.USA, 3rd House On the Right.
Beautiful job of troubleshooting. My Icom IC-7800 had the switching supply go out a couple years ago. I watched your video teaching about various switching supply topography. I was able to muddle through it and get it fixed in large part because of your previous video. That was made extra difficult because Icom won't provide the schematic or parts. They consider that 3rd party supply a field replacable unit at $1650! It turned out that among several bad components were 2 proprietary hybrid ICs which I could not source. After much research, I found that Yaesu also uses Futaba for some of their power supplies and one of their stand alone supplies used that same custom chip. At $75 a piece, I ordered them from Yaesu, they had to order them from Japan, I soldered them in, held my breath, and the radio fired up. Thanks for your help 🙂
I have the same on my desk. On mine, the fan starts full blow and then it settles to a low rpm. Good device, I never had to adjust the noise but I work mostly on 10m so... Greet repair, Peter!
Nice job again, Peter! You could have used an ESR meter as a "pre-test" for the double diode on the output side, as to not measure the transformer winding. I very much favour linear psu's in radio equipment, as the switchers most often generate noise in a sensitive SW receiver. Then again, the switch mode ones are much lighter with same power output..
Good vids, just a tip, always start by firmly stating the current issues with equipment along with any other know info that might help ie. customer said it produced smoke just before quitting. :}
Well done. Thank you. They are a pain to repair in my opinion. Most of the ones I have seen are so cheaply made you end up rebuilding a lot of the stages. Thanks for your videos....From an old tech.
Nice work Peter. I to was fooled by the beeps....i dont habe a high power smps on my bench, just a linear type with an external crowbar added but reading the coments about them here i may grab one. Plenty of smaller ones for various things though and ha ent had noise issues as if yet.
Excellent video. I see very similar power supplies sold here in the States for very inexpensive prices. Personally I'll stick with Samlex brand SMPS, I don't trust these cheap supplies with my valuable equipment...
Personally I don't trust my valuable equipment to SMPS at all but if I have a choice. A useful basic rule is that if it needs a 'noise' offset then it's garbage and spewing RF all over the place.
@@M0UAW_IO83 I'll take a quality SMPS over a linear any day. One shorted pass transistor and you better hope the supply has a fast enough crowbar protection circuit, otherwise you've got unregulated DC from the rectifier going directly to your equipment. On the other hand, with an SMPS, the high voltage DC is galvanically isolated from the regulated DC side so an overvolt failure mode is virtually impossible. I've used numerous high quality SMPS supplies for years, operating from 160 meters to 23CM, and never once had an issue with RFI. I do agree the knob to adjust the switching frequency so you can move the spurs around is a sign of a junk PSU. It's not difficult for a manufacturer to tame SMPS RFI with proper shielding, common mode chokes, and a handful of bypass caps.
Meins konnte ich nicht mehr reparieren, es war voller Gelber klebe Grütze (NP 75€) Aber mein altes HAMA Netzteil von 1980 20A ist unverwüstlich mit seinem Trafo.
To properly test the fan operation under load, you should have installed the top half of the enclosure, to ensure proper air flow, that way the fan would likely have come on sooner.
If you get a chance, I'd love to hear about the noise spectra on the DC output. This model (and similar such as "PSU1228") are quite affordable. But how much RF is produced? Enough RF that they include a noise offset knob, but how much? Great video, thanks again for another entertaining moment while I clean the kitchen!
Will do it with the next repair on this device. Generally spoken, a lot of those power supplies are in the market, but we have got never bad feedback on the noise..
I don't trust switching supplies for radio. I have seen that some have these variable noise suppressors / filters to chase the noise away. Has anyone done a video on how well these work? Are they really always quiet or do you have to keep adjusting them?
Thank you, Peter! Looks like a real tedious process to disassemble!! Can someone recommend a decent isolation transformer as stated at the 13:58 mark? Just want to plan ahead, should the job arise. Thank you for the guidance!
Another fantastic and informative video, thanks as always. By the way Peter, we have an identical psu at home running our cb. The problem is, that it has a broken "needle meter". This has happened out of the warranty period. Do you, or anyone reading this post, have any idea where we can obtain a replacement meter please? Many Thanks 73's Wayne, Barbara and Nina. ❤️❤️👍👍👍👍🤔🤔🤔🤔😊😊😊😊😊
Well, to be honest, the display is a bit of a gimick anyways. I'll just leave it in place and pretend that it doesn't exist!!!! Lol!!! Cheers and 73's good buddy. Wayne, Nina & Barbara ❤️❤️👍👍❌️❌️
Since I have zero knowledge of Switching Power Supply Designs...a Schematic at the outset would have allowed me to follow along intelligently. In the end, decent design and components, but shoddy soldering.?
