VOGONS


First post, by GabrielKnight123

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I just blew a fuse in a new old stock power supply its had no more than 10 hours of operation I can replace the fuse no problems there but now i'm worried it would happen again if there is something else wrong with it, does anyone know if this is a common thing and what to try to fault find it? Is this brand of PS cheaply made or is it decent? At the moment of blow out I had a VLB video card, sound blaster card, two controller cards one for serial mouse and the other for a single HDD and a DVD drive with a floppy drive, the front panel getting 5 volts for the display, and I think 12 volts for the CPU fan so the power supply wasnt getting a lot of strain. In the pics below the big capacitor on the right is oh so slightly bulging but i'm not sure about it. Should I repair this PS or pass it on to silicone chip heaven?

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Reply 3 of 17, by retardware

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Thick brown goo between the PCB and the primary's electrolytic caps. Really colophonium?
It's clearly visible that both of them are under internal pressure.
Maybe they didn't like being powered up so harshly after decades of rest.
I'd change the caps and replace the fuse, this time using a fuse holder. Often the soldering heat degrades such cheap fuses, which then blow for no apparent reason.

Reply 4 of 17, by ph4nt0m

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This one looks like a poor noname 200W AT power supply. Half bridge with a manual 230V/115V switch. Mising some input filters, varistors for surge protection and the caps don't look great either. A blown fuse means there is a blown bipolar transistor or dual diode most likely. Sure thing it can be repaired with appropriate skills and about an hour of free time. Although I suggest you just to buy an ATX to AT power cable for a few bucks and use it with a decent ATX power supply.

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Reply 5 of 17, by GabrielKnight123

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Ok everyone thanks for the information and unfortunately there is no room in the case to put an adapter in I will keep the fan and throw away the rest since my suspicion of being a cheap piece of crap is confirmed, the brown goo isnt sticky or anything and it seems to be all over the PCB it comes off with some cleaner and looks like the transformers were sealed with this and looks like a resin of some sort. When the fuse blew being next to the fan it looked like a sports cars exhaust with flames I just hope the rest of the PC is undamaged.

Reply 6 of 17, by retardware

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@phantom
Sure it is only a half bridge rectifier? To me the part right of C2 looks like a full bridge. And I saw very very few power supplies back then that had filters at all...

@OP
In my view this is just a common taiwanese PSU. And definitely one of the better ones of that time. They were (and are) really generous with that colophonium (natural resin, used to improve solder flux), which looks like brown goo. It is not aesthetic but usually harmless. What I worried about was the dark brown under the caps.

Back then when the AT form factor died out and replacement AT power supplies became scarce, I repaired AT power supplies by taking an ATX power supply board, unsolder the ATX power connector and instead solder in the P8/P9 AT cable. When I did that, I usually added some more drive cables, too, including 3.5" cable.
When connecting the fan, I took care to connect it directly to 12V, as many ATX power supplies have thermal fan regulation. Which is bad imho.
Finally, I put the ATX power supply board into the AT power supply case. This always worked with standard power supplies, where power supply boards seem all the same size.

Reply 7 of 17, by ph4nt0m

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retardware wrote:

@phantom
Sure it is only a half bridge rectifier? To me the part right of C2 looks like a full bridge. And I saw very very few power supplies back then that had filters at all...

It isn't about a rectifier. That's a regular diode bridge to the right of C2. It's about topology. There are two 200V bulk caps with balancing resistors and those two yellow wires to a 230V/115V voltage doubling switch. The heat spreader behind the bulk caps is too small for 4 BJTs. Seems a generic half bridge on 2 BJTs.

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Reply 9 of 17, by retardware

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Wow.
This image shows how puny this PSU really is.

Many ATX PSU's have way more and longer cables. This together with an additional adapter consuming even more room isn't really an option in your case.
Just unsoldering the cables from a new decent ATX PSU board, and then putting in the cables taken from the original power supply at least makes for an optically perfect restoration. (Only recommended for people with some skill and experience in electronics)

Reply 10 of 17, by gdjacobs

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Your first step should be checking the caps, MOV, and diode pack for any dead shorts.

All hail the Great Capacitor Brand Finder

Reply 11 of 17, by DAVE86

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gdjacobs wrote:

Your first step should be checking the caps, MOV, and diode pack for any dead shorts.

Yeah. Definately a short in the primary. That fuse wire just evaporated inside the glass. In an overcurrent event it would just break open.
Visually the Q1 Q2 BJTs seem fine. Probalby the primary C2 C3 caps are rotting inside and shorted.

Btw it looks like an OK 200W half bridge unit. Lacking a full EMI input stage but it's only two extra Line and Neutral coils so it forgivable.
To me the main transformet seems like a big E core maybe 39, 42 size. That's enough for 300W unit!
IC1 TL494 does the primary switching IC2 is probably supervisor nnd power good generator. It's decent despite the aging bad caps.

Reply 12 of 17, by SirNickity

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I would concur. The first pic did look like one of the mains-side reservoir caps was failing. If that's the case, it could have failed short, and that would explain the fuse. Now hopefully the fuse failed without any of the other active components getting damaged in the process. If so, it should be good to go after a re-cap. It looks like an OK (if not great) supply to me.

Reply 13 of 17, by DAVE86

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Actually it looks exactly like a HS 200 (High Perfection Technologies) Unit.

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One of their redundant 300W AT units:

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I'm not sure who are the OEM behind these though...

If you have the parts and know-how just replace the primary caps and fuse and see if it works.

Reply 14 of 17, by GabrielKnight123

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I tried a couple of stores that I could drive to but they dont have any in this range on the old caps is "85 degrees 330 uf 250 volts" are these caps electrolytic capacitors or some other type as now I would like to give it a go fixing it from what everyone said about it being a good/decent PS.

Reply 15 of 17, by Deksor

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Buy the online (farnell, mouser ...) Caps they sell in stores these days are often shit and too expensive for what they are

Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 16 of 17, by DAVE86

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GabrielKnight123 wrote:

I tried a couple of stores that I could drive to but they dont have any in this range on the old caps is "85 degrees 330 uf 250 volts" are these caps electrolytic capacitors or some other type as now I would like to give it a go fixing it from what everyone said about it being a good/decent PS.

These are aluminum electrolytic capacitors. If you buy them online make sure the caps also match physical size like height and diameter so they'll fit on the circuit board. Also you don't need to keep the exact parameters. You can look for 105C degrees 330uF 200V or higher capacitance value like 470uf 200V.

Reply 17 of 17, by SirNickity

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My procedure is to make a list of all the capacitors I remove as I pull them from the PCB. Note the designator (e.g., C2), the rating (330u, 200V), the pin spacing (10mm), the diameter (22mm), and the height. The height is usually the parameter that can vary the most, assuming there's no constraint due to overhead heatsinks or whatever.

For the film capacitors (I replace all primary-side film caps as well), note the designator, capacity, voltage rating (you might see both AC and/or DC ratings -- source your replacement based on AC rating of 250V or higher), pin spacing, LxWxH, and safety rating. There should be a mark that says X2 or X1Y1 or something like that. Try to match it like-for-like, or read up on what the rating means and make sure you understand where you can substitute.

For ceramic disc capacitors, it's much the same as the film caps. Capacity (usually expressed as a three-digit code, like 472 -- look it up or use an online calculator to convert), AC voltage rating, pin spacing, approximate size (if there's anything nearby), and safety rating.

On Digikey, I filter first by brand (I stick to Nichicon), through-hole, in stock, the exact capacity and pin spacing, then hit search and refine what's left to remove packaging that I can't buy (e.g., tape-and-reel -- high quantity stuff like that), then diameter (equal or thinner), height (if it matters), search again. Then, I select 105C parts only, and refine that to only those that specify lifetimes of at LEAST 3000 hours @ 105C. If I can't find anything in a suitable (or higher) voltage rating at that temperature and lifetime spec, I will bend to 2000 hours @ 105C, but that's pretty rare.

Film and ceramic caps are usually so plentiful that I substitute exactly the same specs just to limit to the dozen or so contenders, then I pick the pretty blue one as a tie-breaker.